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Role of minerals, ions and
water in life processes
Minerals
• The mineral (inorganic) elements constitute
only a small proportion of the body weight.
• There is a wide variation in their body content.
For instance, calcium constitutes about 2% of
body weight while cobalt about 0.00004%.
General functions:
• Mineral perform several vital functions which are absolutely
essential for the very existence of the organism.
• These include calcification of bone, blood coagulation,
neuromuscular irritability, acid-base equilibrium, fluid
balance and osmotic regulation.
• Certain mineral are integral components of biologically
important compounds such as hemoglobin (Fe), thyroxine
(I), insulin(Zn) and vitamin B12(Co).
• Sulfur is present in thiamine, biotin, lipoic acid and
coenzyme A.
• Several minerals participates as cofactors for enzymes in
metabolism (e.g. Mg, Mn, Cu, Zn, K).
• Some elements are essential constituents of certain enzymes
(e.g. Co, Mo, Se)
Classification
• The minerals are classified as principal elements and trace
elements. The seven principal elements (macro-minerals)
constituents 60-80% of the body’s inorganic material. These
are calcium, phosphorus, magnesium, sodium, potassium,
chloride and sulfur.
• The principal elements are required in amounts greater than
100 mg/day. The micro-minerals are required in amounts less
100mg/day. They are subdivided into three categories.
• Essential trace elements : Iron, copper, iodine, manganese,
zinc, molybdenum, cobalt, fluorine, selenium and chromium.
• Possibly essential trace elements: Nickel, vanadium, cadmium
and barium.
• Non-essential trace elements: Aluminium, lead, mercury,
boron, sliver, bismuth etc.
Macro-elements
• Calcium
• Phosphorus
• Magnesium
• Sodium
• Potassium
• Chlorine
• Sulfur
Calcium
• Calcium is the most abundant among the
minerals in the body.
• The total content of calcium in an adult man is
about 1 to 1.5kg. As much as 99% of it is
present in the bones and teeth.
• A small fraction (1%) of the calcium, found
outside the skeletal tissue, performs a wide
variety of functions.
Biochemical functions
• Development of bones and teeth: Calcium, along with
phosphate, is required for the formation (of hydroxyapatite)
and physical strength of skeletal tissue. Bone is regarded as a
mineralized connective tissue. Bones which are in dynamic
state serve as reservoir of Ca. Osteoblasts result in
demineralization.
• Muscle contraction: Ca+ interacts with troponin C to trigger
muscle contraction. Calcium also activates ATPase, increases
the interaction between actin and myosin.
• Blood coagulation: Several reactions in the cascade of blood
clotting process are dependent on Ca+ (factor IV)
• Nerve transmission: Ca+ is necessary for the transmission of
nerve impulse.
• Membrane integrity and permeability: Ca+ influences the
membrane structure and transport of water and several ions
across it.
Biochemical functions
• Activation of enzymes: Ca+ is needed for the direct activation
of enzymes such as lipase (pancreatic), ATPase and succinate
dehydrogenase.
• Calmodulin mediated action of Ca2+: Calmodulin (mol. wt.
17,000) is a calcium binding regulatory protein. Ca-
calmodulin complex activates certain enzymes e.g. adenylate
cyclase, Ca2+ dependent protein kinase, myosin kinase,
phospholipase C, glycogen synthase.
• Calcium as intracellular messenger: Certain hormones exert
their action through the mediation of Ca2+ (instead of
cAMP). Calcium is regarded as a second messenger for such
hormonal action e.g. epinephrine in liver glycogenolysis.
Calcium serves as a third messenger for some hormones e.g.
antidiuretic hormone (ADH) acts through cAMP, and then
Ca2+.
Biochemical functions
• Release of hormones: The release of certain hormones
(insulin, PTH, calcitonin) form the endocrine glands is
facilitated by Ca2+.
• Secretory processes: Ca2+ regulate microfilament and
microtubule mediated processes such as endocytosis,
exocytosis and cell motility.
• Contact inhibition: Calcium is believed to be involved
in cell to cell contact and adhesion of cells in a tissue.
The cell to cell communication may also required Ca2+.
• Action on heart: Ca2+ acts on myocardium and prolongs
systole.
Dietary requirements
• Adult man and women – 800mg/day
• Women during pregnancy, lactation , post-
menopause – 1.5g/day
Sources:
• Best source –Milk and milk products
• Good source – Beans, leafy vegetables, fish,
cabbage, egg yolk.
Deficiency/disease states
• The blood Ca level is maintained within a
narrow range by the homeostatic control, most
predominantly by PTH. Hence abnormalities
in Ca metabolism are mainly associates with
alteration in PTH.
• Hypercalcemia
• Hypocalcemia
Hypercalcemia
• Elevation in serum Ca level (normal 9-11 mg/dl) is
hypercalcemia.
• Hypercalcemia is associated with
hyperparathyroidism caused by increased activity
of parathyroid glands.
• Decreased in serum phosphate (due to increased
renal loss) and increase in alkaline phosphate
activity are also found in hyperparathyroidism.
• Elevation in the urinary excretion of Ca and P,
often resulting in the formation of urinary calculi,
is also observed in these pateints.
Hypercalcemia
• The determination of ionized serum calcium
(elevated or 6-9mg/dl) is more useful for the
diagnosis of hyperparathyroidism.
• It has been observed that some of the patients may
have normal levels of total calcium in the serum but
differ with regard to ionized calcium.
• The symptoms of hypercalcemia include lethargy,
muscle weakness, loss of appetite, constipation,
nausea, increased myocardial contractility and
susceptibility to fracture.
Hypocalcemia
• Hypocalcemia is a more serious and life threatening
condition. It is characterized by a fall in the serum
Ca to below 7mg/dl, causing tetany.
• The symptoms of tetany include neuromuscular
irritability, and convulsions.
• Hypocalcemia is mostly due to hypoparathyroidism.
This may happen after an accidental surgical
removed of parathyroid glands or due to an
autoimmune disease.
• Treatment: Supplementation of oral calcium with
vitamin D is commonly employed. In severe cases
of hypocalcemia , calcium gluconate is
intravenously administered.
Rickets
• Rickets is a disorder of defective calcification of
bones.
• This may be due to a low levels of vitamin D in
the body or due to a dietary deficiency of Ca
and P or both.
• The concentration of serum Ca and P may be
low or normal.
• An increase in the activity of or normal.
• An increase in the activity of alkaline
phosphatase is a characteristic feature of rickets.
Renal rickets
• Renal rickets is associated with damage to renal
tissue, causing impairment in the synthesis of
calcitriol.
• It does not respond to vitamin D in ordinary
doses, therefore, some workers regard this as
vitamin D resistant rickets.
• Renal rickets can be treated by administration of
calcitriol.
Osteoporosis
• Osteoporosis is characterized by demineralization of
bone resulting in the progressive loss of bone mass.
• Occurrence: The elderly people (over 60yr.) of both
sexes are at risk for osteoporosis. However, it more
predominantly occurs in the post- menopausal
women.
• Osteoporosis results in frequent bone fractures which
are a major cause of disability among the elderly.
• It is estimated that more than 50% of the fractures in
USA are due to this disorder. Osteoporosis may be
regarded as a silent thief.
Treatment
• Estrogen administration along with calcium
supplementation (in combination with vitamin
D) to postmenopausal women reduces the risk
of fractures.
• Higher dietary intake of Ca (about 1.5g/dl) is
recommended for elderly people.
Osteopetrosis (marble bone disease)
• Osteopetrosis is characterized by increased bone
density.
• This is primarily due to inability to resorb bone.
• This disorder is mostly observed is mostly
observed in associated with renal tubular
acidosis (due to a defects in the enzyme carbonic
anhydrase)and cerebral calcification.
Phosphorus
• An adult body contains about 1kg phosphate and
it is found in every cell of the body.
• Most of it (about 80%) occurs in combination
with Ca in the bones and teeth.
• About 10% of body P is found in muscles and
blood in association with proteins, carbohydrates
and lipids.
• The remaining 10% is widely distribution in
various chemical compounds.
Biochemical functions
• Phosphorus is essential for the development of bones and
teeth.
• It plays a central role for the formation and utilization of high-
energy phosphate compounds e.g. ATP, GTP, creatine
phosphate etc.
• Phosphorus is required for the formation of phospholipids,
phosphoproteins and nucleic acids (DNA and RNA)
• It is as essential component of several nucleotide coenzymes
e.g. NAD+, NADP+, pyridoxal phosphate, ADP, AMP.
• Several proteins and enzymes are activated by
phosphorylation.
• Phosphate buffer system is important for the maintenance of
pH in the blood (around 7.4) as well as in the cells.
Dietary requirement
• The recommended dietary allowance (RDA) of
phosphate is based on the intake of calcium.
• The ratio of Ca: P of 1:1 is recommended (i.e.
800mg/day) for an adult.
• For infants, however, the ratio is around 2:1,
which is based on the ratio found in human milk.
• Calcium and phosphate are distributed in the
majority of nature foods in 1:1 ratio.
• Therefore, adequate intake of Ca generally takes
care of the P requirement also
Sources
• Milk, cereals, leafy vegetables, meat, eggs.
Deficiency/disease states
• Serum phosphate level is increased in
hypoparathyroidism and decreased in hyperpara-
thyroidism.
• In severe renal diseases, serum phosphate content is
elevated causing acidosis.
• Vitamin D deficient rickets is characterized by
decreased serum phosphate (1-2mg/dl).
• Renal rickets is associated with low serum phosphate
levels and increased alkaline phosphatase activity.
• In diabetes mellitus, serum content of organic
phosphate is lower while that of inorganic phosphate is
higher.
Magnesium
• The adult body contains about 20 g magnesium,
70% of which is found in bones in combination
with calcium and phosphorus. The remaining 30%
occurs in the soft tissues and body fluid.
• Biochemical functions:
• Magnesium is required for the formation of bones
and teeth.
• Mg2+ serves as a cofactor for several enzymes
requiring ATP e.g. hexokinase, glucokinase,
phosphofructokinase, adenylatecyclase.
• Mg2+is necessary for proper neuro-muscular
function. Low Mg2+ levels lead to neuromuscular
irritability.
Dietary requirement
• Adult man – 350mg/day
• Adult women – 300mg/day
• Sources:
• Cereals, nuts, beans, vegetables (cabbage, cauliflower),
meat, milk, fruits.
• Deficiency/disease states:
• Magnesium deficiency causes neuro-muscular irritation,
weakness and convulsions.
• These symptoms are similar to that observed in tetany
(Ca deficiency) which are relieved only by Mg.
Malnutrition, alcoholism and cirrhosis of liver may lead
to Mg deficiency.
• Low levels of Mg may be observed in uremia, rickets and
abnormal pregnancy.
Sodium
• Sodium is the chief cation of the extracellular fluid. About
50% of body sodium is present in the bones, 40% in the
extracellular fluid and the remaining (10%)in the soft
tissues.
• Biochemical functions:
• In association with chloride and biocarbonate, sodium
regulates the body’s acid-base balance.
• Sodium is required for the maintenance of osmotic
pressure and fluid balance.
• It is necessary for the normal muscle irritability and cell
permeability.
• Sodium is involved in the intestinal absorption of glucose,
galactose and amino acids.
• It is necessary for initiating and maintaining heart beat.
Dietary requirements
• For normal individuals, the requirement of sodium is
about 5-10 g/day which is mainly consumed as
NaCl.
• For persons with a family history of hypertension,
the daily NaCl intake should be less than 5g.
• For patients of hypertension, around 1g/day is
recommended.
• It may be noted that 10g of NaCl contains 4g of
sodium.
• The daily consumption of Na is generally higher
than required due to its flavor
Sources
• The common salt (NaCl) used in the cooking
medium is the cooking medium is the major
source of sodium.
• The ingested foods also contribute to sodium.
• The good sources of sodium include bread,
whole grains, leafy vegetables, nuts eggs and
milk.
Deficiency/disease states
• Hyponatremia
• This is a condition in which the serum sodium level
falls below the normal.
• Hyponatremia may occur due to diarrhea, vomiting,
chronic renal diseases, adrenocortical insufficiency
(Addison’s disease).
• Administration of salt free fluids to patients may also
cause hypoaremia.
• This is due to overhydration.
• Deceased serum sodium concentration is also observed
in edema which occurs in cirrhosis or congestive heart
failure.
• The manifestations of hyponatremia include reduced
blood pressure and circulatory failure.
Hypernatremia
• This condition is characterized by an elevation in the serum
sodium level.
• They symptoms include increase in blood volume and blood
pressure.
• It may occur due to hyperactivity of adrenal cortex (Cushing’s
syndrome), prolonged administration of cortisone, ACTH and /or
sex hormones.
• Loss of water from the body causing dehydration, as it occurs in
diabetes insipidus, results in hypernatremia. Rapid administration
of sodium salts also increases serum sodium concentration.
• It may be noted that in pregnancy, steroid and placental hormones
cause sodium and water retention in the body, leading to edema.
• In edema, along with water, sodium concentration in the body is
also elevated. Administration of diuretic drugs increases the
urinary output of water along with sodium.
• In the patients of hypertension and congestive cardiac failure salt
(Na+) restriction is advocated.
Potassium
• Potassium is the principal intracellular cation. It is
equally important in the extracellular fluid for specific
functions.
• Biochemical functions:
• Potassium maintains intracellular osmotic pressure.
• It is required for the regulation of acid-base balance and
water balance in the cells.
• The enzyme pyruvate kinase (of glycolysis) is dependent
on K+ for optimal activity.
• Potassium is required for the transmission of nerve
impulse.
• Adequate intracellular concentration K+ is necessary for
proper biosynthesis of proteins by ribosomes.
• Extracellular K+ influence cardiac muscles activity.
Dietary requirements
• About 3-4 g/days
• Sources:
• Banana, orange , pineapple, potato, beans,
chicken and liver. Tender coconut water is a
rich source of potassium.
Deficiency/disease states
• Serum potassium concentration is maintained within a
narrow range. Either high or low concentrations are
dangerous since potassium effects the contractility of
heart muscle.
• Hypokalemia: Decreased in the concentration of serum
potassium is observed due to overactivity of adrenal
cortex (Cushing’s syndrome), prolonged cortisone
therapy, intravenous administration of K+ free fluids,
treatment of diabetic coma with insulin, prolonged
diarrhea and vomiting. The symptoms of hypokalemia
include irritability, muscular weakness, tachycardia ,
cardiomegaly and cardiac arrest. Changes in the ECG
are observed (flattened waves with inverted T wave)
Hyperkalemia
• Increase in the concentration of serum potassium
is observed in renal failure, adrenocortical
insufficiency (Addison’s disease), diabetic coma,
severe dehydration, intravenous administration of
fluids with excessive potassium salts.
• The manifestations of hyperkalemia include
depression of central nervous system, mental
confusion, numbness, bradycardia with reduced
heart sounds and finally, cardiac arrest. Changes in
ECG are also observed (elevated T wave).
Chlorine
• Chlorine is a constituent of sodium chloride. Hence,
the metabolism of chlorine and sodium are
intimately related.
• Biochemical functions:
• Chlorine is involved in the regulation of acid-base
equilibrium, fluid balance and osmotic pressure.
These functions are carried out by the interaction of
chlorine with Na+ and K+.
• Chlorine is necessary for the formation of HCL in
the gastric juice.
• Chlorine shift involved the active participation of
Cl-.
• The enzyme salivary amylase is activated by
chloride.
Dietary requirement
• The daily requirement of chloride as NaCl is 5-10g.
Adequate intake of sodium will satisfy the chloride
requirement of the body.
• Sources:
• Common salt as cooking medium, whole grains,
leafy vegetables, eggs and milk.
• Deficiency/disease states:
• Hypochloremia: A reduction in the serum Cl- level
may occur due to vomiting, diarrhea, respiratory
alkalosis, Addison’s disease and excessive sweating.
• Hyperchloremia: An increase in serum Cl-
concentration may be due to dehydration, respiratory
acidosis and Cushing’s syndrome.
Sulfur
• Sulfur of the body is mostly present in the organic
form. Meithionine, cysteine and cysteine are the three
sulfur-containing amino acids present in the proteins.
Generally, proteins contains about 1% sulfur by
weight.
• Biochemical functions:
• Sulfur-containing amino acids are very essential for the
structural conformation and biological functions of
proteins (enzymes, hormones, structural proteins etc.).
The disulfide linkages( -S – S-) and sulfhydryl groups
(- SH) are largely responsible for this.
• The vitamins thiamine, biotin, lipoic acid, and
coenzyme A of pantothenic acid contain sulfur.
Biochemical functions
• Heparin, chondroitin sulfate, glutathione,
taurocholic acid are some other important sulfur-
containing compounds.
• Phosphoadenosine phosphosulfate(PAPS) is the
active sulfate utilized for several reactions e.g.
synthesis of glycosaminoglycans, detoxification
mechanism.
• The sulfur-containing amino acid methionine (as S-
adenosylmethionine) is actively involved in
transmethylation reactions.
Dietary requirements
• Dietary requirements:
• There is no specific dietary requirement for sulfur.
• Sources:
• Adequate intake of sulfur-containing essential
amino acid methionine will meet the body need.
Food proteins rich in methionine and cysteine are
the sources of sulfur.
Deficiency / disease states:
• Sulfur is part of methionine and cysteine, which are
amino acids needed in the making of proteins. So,
if there is too little sulfur, or a sulfur deficiency, it
could lead to reduced protein synthesis.
• The sulfur-containing amino acid cysteine is also
needed for making glutathione, which is somewhat
of a superhero in body because it works as a potent
antioxidant that protects cells from damage. So we
see that a sulfur deficiency can cause a cascade of
other problems. For instance, without sufficient
sulfur to make cysteine, there could be reduced
glutathione synthesis, which may contribute to cell
damage
Deficiency / disease states:
• Sulfur is also needed to create connective
tissues that support joints, such as cartilage,
tendons and ligaments.
• So, connection, have a deficiency of sulfur
could contribute to joint pain or disease.
• In fact, sulfur contained in medications designed
for joint health.
Micro-elements
• Iron
• Copper
• Iodine
• Manganese
• Zinc
• Molybdenum
• Cobalt
• Fluorine
• Selenium
• Chromium
Iron
• The total content of iron is an adult body id 3-5g. About
70% of this occurs in the erythrocytes of blood as a
constituent of hemoglobin.
• At least 5% of body iron is present in myoglobin of
muscle.
• Heme is the most predominant iron containing
substance.
• It is a constituent of several proteins/enzymes
(hemoproteins)- hemoglobin, myoglobin, cytochromes,
xanthine oxidase, catalase, tryptophan pyrrolase,
peroxidase.
• Certain other proteins contain non-heme ion e.g.
transferrin, ferritin, hemosiderin.
Biochemical functions
• Iron mainly exerts its functions through the
compounds in which it is present. Hemoglobin and
myoglobin are required for the transport of O2 and
CO2.
• Cytochromes and certain non-heme proteins are
necessary for electron transport chain and oxidative
phosphorylation.
• Peroxidase, the lysosomal enzyme, is required for
phagocytosis and killing of bacteria by neutrophils.
• Iron is associated with effective immuno-
competence of the body.
Dietary requirements
• Adult man –10 mg/day
• Menstruating woman – 18 mg/day
• Sources:
• Rich sources – Organ meats (liver, heat, kidney).
• Good sources – Leafy vegetables, pulses,
cereals, fish, apples, dried fruits, molasses,
jaggery.
• Poor sources – Milk, wheat, polished rice.
Disease states
• Iron deficiency anemia: :This is the most prevalent
nutritional disorder worldover, including the well developed
countries (e.g. USA).
• Several factors may contribute to iron deficiency anemia.
• These include inadequate intake or defective absorption of
iron, chronic blood loss, repeated pregnancies and
hookworm infections.
• Strict vegetarian are more prone for iron deficiency anemia.
This is due to the presence of inhibitors of iron absorption in
the vegetarian foods, besides the relatively low content of
iron. Iron deficiency anemia mostly occurs in growing
children, adolescent girls, pregnant and lactating women. It
is characterized by microcytic hypochromic anemia with
reduced blood hemoglobin levels(<12g/dl). The other
manifestation include apathy (dull and inactive), sluggish
metabolic activities, related growth and loss of appetite.
• Treatment: Iron deficiency is treated by supplementation of
iron along with folic acid and vitamin C.
Disease states
• Hemosiderosis:
• This is a less common disorder and is due to excessive
iron in the body, frequently referred to as iron toxicity.
• It is commonly observed in subjects receiving
repeated blood transfusions over the years, e.g.
patients of hemolytic anemia, hemophilia.
• As already stated, iron is a one-way compound, once it
enters the body, it cannot escapes.
• Excessive iron is deposited as ferritin and
hemosiderin. Hemosiderosis is commonly observed
among the bantu tribe in south Africa.
• This is attributed to a high intake of iron from their
staple diet corn and their habit of cooking food in iron
pots.
Disease states
• Hemochromatosis: This is a rate disease in which
iron is directly deposited in the tissues (liver,
spleen, pancreas and skin).
• Hemosiderosis is sometimes accompanied by
hemochromatosis.
• Bronzed- pigmentation of the skin, cirrhosis of
liver, pancreatic fibrosis are the manifestations of
this disorder.
• Hemochromatosis causes a condition known as
bronze diabetes.
Copper
• The body contains about 100mg copper distributed in
different organs. It is involved in several important functions.
• Biochemical functions:
• Copper is an essential constituent of several enzymes. These
include cytochrome oxidase, catalase, tyrosine, superoxide
dismutase, monoamine oxidase, ascorbic acid oxidase, ALA
synthase, phenol oxidase and uricase. Due to its presence in
a wide variety of enzymes, copper is involved in many
metabolic reactions.
• Copper is necessary for the synthesis of hemoglobin (Cu is a
constituent of ALA synthase, needed for heme synthesis).
• Lysyl oxidase ( a copper containing enzyme) is required for
the conversion of certain lysine residues of collagen and
elastin to allysine which are necessary for cross-linking these
structural proteins.
Biochemical functions
• Ceruloplasmin serves as ferroxidase and is involved in
the conversion of iron from Fe2+ to Fe3+ in which form
iron (transferrin) is transported in plasma.
• Copper is necessary for the synthesis of melanin and
phospholipids.
• Development of bone and nervous system (myelin)
requires Cu.
• Certain copper containing non-enzymatic proteins have
been identified, although their functions are not
clearly known. These include hepatocuprein (storage
form in liver), cerebrocuprein (in brain) and
hemocuprein (in RBC).
• Hemocyanin, a copper protein complex in
invertebrates, functions like hemoglobin for O2
transport.
Dietary requirements
• Adults – 2-3 mg/day
• Infants and children – 0.5-2 mg/day
• Sources:
• Liver, kidney, meat, egg yolk, cereals, nuts and
green leafy vegetables. Milk is a poor source.
Deficiency /disease states
• Copper deficiency: Several deficiency of copper
causes demineralization of bones, demyelination of
neural tissue, anemia, fragility of arteries,
myocardial fibrosis, hypopigmentation of skin,
greying of hair.
• Menke’s disease: This disorder is due to a defect in
the intestinal absorption of copper. It is possible that
copper may be trapped by metallothionein in the
intestinal cells. The symptoms of Menke’s disease
include decreased copper in plasma and urine,
anemia and depigmentation of hair.
Deficiency /disease states
• Wilson’s disease: Wilson’s disease (hepatolenticular
degeneration) is a rare disorder (1:50,000) of abnormal
copper metabolism and is characterized by the following
manifestations.
• Copper is deposited in abnormal amounts in liver and
lenticular nucleus of brain. This may lead to hepatic cirrhosis
and brain necrosis.
• Low levels of copper and ceruloplasmin in plasma (reference
range 20-50mg/dl) with increased excretion of copper in
urine.
• Copper deposition in kidney causes renal damage. This leads
to increased excretion of amino acid, glucose, peptides and
hemoglobin in urine.
• Intestinal absorption of copper is very high, about 4-6 times
higher than normal.
Iodine
• The total body contains about 20mg iodine most
of it (80%) being present in the thyroid gland.
Muscle, salivary glands and ovaries also contain
some amount of iodine.
• Biochemical functions:
• The only known function of iodine is its
requirement for the synthesis of thyroid
hormones namely, thyroxine (T4) and
trriodothyronine (T3). T3 is more active in its
biological functions than T4.
Biochemical functions
• Influence on the metabolic rate: Thyroid hormones
stimulate the metabolic activities and increases the
oxygen consumption in most of the tissues of the
body (exception- brain, lungs, testes and retina)
• Effect on protein synthesis: Thyroid hormones act
like steroid hormones in promoting protein
synthesis by acting at the transcriptional level
(activated DNA to produce RNA). Thyroid
hormones, thus, function as anabolic hormones and
cause positive nitrogen balance and promote
growth and development.
Biochemical functions
• Influence on carbohydrate metabolism: Thyroid
hormones promote intestinal absorption of glucose
and its utilization. These hormones increase
gluconeogenesis and glycogenolysis, with an overall
effect of enhancing blood glucose level
(hyperglycemia).
• Effect on lipid metabolism: Lipid turnover and
utilization are stimulated by thyroid hormones.
Hypothyroidism is associated with elevated plasma
cholesterol levels which can be reversed by thyroid
hormone administration.
Dietary requirements
• Adults- 100-150µg/day
• Pregnant women - 200µg/day
• Sources:
• Sea foods, drinking water, vegetables, fruits (grown
on seaboard). High altitudes are deficient in iodine
content in water as well as soil. Plant and animal
foods of these areas, therefore, contain lesser
amount of iodine. In these regions iodine is added to
drinking water or table salt.
Deficiency /disease states
• Goiter: Any abnormal increase in the size of the thyroid
gland is known as goiter. Enlargement of thyroid gland
is mostly to compensate the deceased synthesis of
thyroid hormones and is associated with elevated TSH.
Goiter is primarily due to a failure in the auto
regulation of T3and T4 synthesis. This may be caused
by deficiency or excess of iodine.
• Goitrogenic substances (goitrogens): These are the
substances that interfere with the production of thyroid
hormones. These include thiocyanates, nitrates and
perchlorates and the drugs such as thiourea, thiouracil,
thiocarbamide etc. certain plant foods – cabbage,
cauliflower and turnip – contain goitrogenic factors
(mostly thiocyanates).
Deficiency /disease states
• Simple endemic goiter: This is due to iodine deficiency
in the diet. It is mostly found in the geographical
regions away from sea coast where the water and soil
are low in iodine content. Consumption of iodized salt
is advocated to overcome the problem of endemic
goiter. In certain cases, administration of thyroid
hormone is also employed.
• Hyperthyroidism: This is also known as thyrotoxicosis
and is associated with over- production of thyroid
hormones. Hyperthyroidism is characterized by
increased metabolic rate (higher BMR) nervousness,
irritability, anxiety, rapid heart rate, loss of weight
despite increased appetite, weakness, diarrhea, sweating
sensitivity to heart and often protrusion eyeballs
(exophthalmos).
Hyperthyroidism
• Hyperthyroidism is caused by Grave’s disease (particularly
in the developed countries) or due to increased intake of
thyroid hormones. Grave’s disease is due to elevated thyroid
stimulating IgG also known as long acting thyroid stimulator
(LATS) which activates TSH and, thereby , increases thyroid
hormonal production.
• Hypothyroidism: This is due to an impairment in the function
of thyroid gland that often causes decreased circulatory
levels of T3 and T4. Disorder of pituitary or hypothalamus
also contribute to hypothyroidism. Women are more
susceptible than men. Hypothyroidism is characterized by
reduced BMR, slow heart rate, weight gain, sluggish
behaviour, constipation, sensitivity to cold, dry skin etc.
Hypothyroidism in children is associated with physical and
mental retardation, collectively known as cretinism.
Manganese
• The total body content of manganese is about 15mg.
The liver and kidney are rich in Mn. Within the cells,
Mn is mainly found in the nuclei in association with
nucleic acids.
• Biochemical functions:
• Mn serve as a cofactor for several enzymes. These
include arginase, pyruvate carboxylase, isocitrate
dehydrogenase, superoxidase dismutase
(mitrochondrial) peptidase.
• Mn is required for the formation of bone, proper
reproduction and normal functioning of nervous
system.
Biochemical functions
• Mn is necessary for the synthesis of
mucopolysaccharides and glycoproetins.
• Hemoglobin synthesis involves Mn.
• Mn inhibits lipid peroxidation.
• Mn is necessary for cholesterol biosynthesis
Dietary requirements
• The exact requirement of Mn is not known. About 2-
9mg/day is recommended for an adult.
• Sources:
• Cereals, nuts ,leafy vegetables and fruits. Tea is rich
sources of Mn.
Deficiency/ disease states
• Mn deficiency in animals causes:
• Retarded growth, bone deformities and, in severe
deficiency, sterility.
• Accumulation of fat in liver.
• Increased activity of serum alkaline phosphatase,
and
• Diminished activity of β- cells of pancreas (low
insulin).
Zinc
• The total content of zinc in an adult blood is about
2g. Prostate gland is very rich in Zn (100mg/g). Zinc
is mainly an intracellular element.
• Biochemical functions:
• Zn is an essential component of several enzymes
e.g. carbonic anhydrase, alcohol dehydrogenase,
alkaline phosphatase, carboxy-peptidase,
superoxidase dismutase (cytosolic).
• Zinc may be regarded as an antioxidant since the
enzyme superoxide dismutase (Zn containing )
protects the body against free radicals damage.
Biochemical functions
• The storage and secretion of insulin form the β-
cells of pancreas require Zn.
• Zn is necessary to maintain the normal levels of
vitamin A in serum. Zn promotes the synthesis of
retinol binding protein.
• It is required for wound healing . Zn enhances
cell growth and division, besides stabilizing
biomembranes.
• Gusten, a zinc containing protein of the saliva, is
important for taste sensation.
• Zn is essential for proper reproduction.
Dietary requirements
• Zinc requirement for an adult is 10 -15
mg/day. It is increased (by about 50%) in
pregnancy and lactation.
• Sources:
• Meat, fish, eggs, milk, beans, nuts.
Deficiency / disease states
• Zinc deficiency is associated with growth
retardation, poor wound healing, anemia, loss of
appetite , loss of taste sensation, impaired
spermatogenesis etc.
• It is reported that Zn deficiency in pregnant
animals causes congenital malformations of the
fetus.
• Deficiency of Zn may result in depression,
dementia and other psychiatric disorders.
• The neuropsychiatric manifestations of chronic
alcoholism may be partly due to zinc deficiency.
Deficiency / disease states
• Acrodermatitis enteropathica is a rare inherited
metabolic disease of zinc deficiency caused by a
defect in the absorption of Zn from, the intestine.
• Zinc toxicity is often observed in welders due to
inhalation of zinc oxide fumes. The
manifestations of Zn toxicity include nausea,
gastric ulcer, pancreatitis, anemia and excessive
salivation.
Molybdenum
• Molybdenum is a constituent of the enzymes xanthine
oxidase, aldehyde oxidase and sulfite oxidase.
• Nitrite reductase (containing Mo)is a plant enzyme,
required for nitrogen fixation.
• The requirements of Mo are not clearly known.
• However, it is widely distributed in the natural foods.
Dietary Mo is effectively (60%-70%) absorbed by the
small intestine.
• Some workers have reported that Mo decreases the
mobilization and utilization of copper in the body.
• Molybdenosis is a rare disorder caused by excessive
consumption of Mo.
• Its manifestations include impairment in growth,
diarrhea and anemia.
• Intestinal absorption of copper is diminished.
Biochemical functions
• The molybdoenzymes in man are sulphite oxidase,
xanthine oxidase/dehydrogenase and aldehyde
oxidase.
• The former is essential for detoxication of the
sulphite arising from metabolism of sulphur-
containing amino acids, from ingestion of
bisulphite preservative and from inhalation of
sulphur dioxide, an atmospheric pollutant.
• The reactions catalysed by xanthine
oxidase/dehydrogenase and aldehyde oxidase are
necessary for human well-being has yet to be
established
Dietary requirements
• Adult men and women is 109 and 76 μg/day
• Sources:
• Legumes, such as beans, lentils, and peas, are the
richest sources of molybdenum. Grain products
and nuts are considered good sources, while
animal products, fruit, and many vegetables are
generally low in molybdenum
Deficiency /Disease states
• The deficiency caused intellectual disability,
seizures, opisthotonus, and lens dislocation.
• Molybdenum deficiency resulting in sulfite
toxicity occurred in a patient receiving long-
term TPN (Total parenteral nutrition).
• Symptoms were tachycardia, tachypnea,
headache, nausea, vomiting, and coma
Cobalt
• Cobalt is only important as a constituent of
vitamin B12 (cobalamin) cobalt content of vitamin
B12 is about 4% by weight.
• The functions of cobalt are the same as that of
vitamin B12.
• Administration of cobalt stimulates the
production of the hormones erythropoietin, which
promotes erythropoiesis.
• Prolonged administration of cobalt is toxic as it
results in polycythemia (increased RBC in
blood).
Biochemical functions
• Cobalt is an essential trace element that is an
integral part of vitamin B12, which is essential in
the metabolism of folic acid and fatty acids.
• Besides cobalt is involved in the production of red
blood cells and is important for the
proper functioning of the nervous system as it can
help in creating a myelin sheath.
• Dietary requirements:
• The average adult intake of cobalt is 5–8 mcg per
day. A safe Recommended Dietary Allowance
(RDA) for cobalt hasn't been set yet.
Sources
• Meat, liver, kidneys, milk, oysters, muscles, fish,
shellfish. Smaller amounts of cobalt are found in
mushrooms (especially shitake). In fruits and
vegetables, usually there are no cobalt (with the
exception of legumes, spinach, cabbage, lettuce,
turnips, cabbage, figs).
• Deficiency /Disease states:
• If you have a cobalt deficiency, this also means you
have a vitamin B-12 deficiency. Anemia is a main
cause of a cobalt deficiency. This is the case with
pernicious anemia. Symptoms can include numbness,
fatigue and tingling in hand and feet.
Fluorine
• Fluorine is mostly found in bones and teeth. The
beneficial effects of fluoride in trace amounts are
overshadowed by its harmful effects caused by excess
consumption.
• Biochemical functions:
• Fluorine prevents the development of dental caries. It
forms a protective layer of acid resistant fluoroapatite
with hydroxyapatite of the enamel and prevents the tooth
decay by bacterial acids. Further, inhibits the bacterial
enzymes and reduces the production of acids.
• Fluorine is necessary for the proper development of
bones.
• It inhibits the activities of certain enzymes. Sodium
fluoride inhibits enolase (of glycolysis) while
fluoroacetate inhibits aconitase (of citric acid cycle).
Dietary requirements
• An intake of less than 2 ppm of fluorine will meet the daily
requirements.
• Sources:
• Drinking water is the main sources.
• Deficiency/Disease states:
• Dental caries: It is clearly established that drinking water
containing less than 0.5ppm of fluoride is associated with
the development of dental caries in children.
• Fluorosis: Excessive intake of fluoride is harmful to the
body. An intake above 2ppm (particularly >5ppm)in
children causes mottling of enamel and discoloration of
teeth. The teeth are weak and become rough with
characteristic brown or yellow patches on their surface.
These manifestations are collectively referred to as dental
fluorosis.
Selenium
• Selenium was originally identified as an element that
causes toxicity to animals (alkali disease) in some parts of
USA, containing large amounts of Se in the soil. Later
work, however, has shown that Se in smaller amounts is
biologically important.
• Biochemical functions:
• Selenium, along with vitamin E, prevents the development
of hepatic necrosis and muscular dystrophy.
• Se is involved in maintaining structural integrity of
biological membranes.
• Se as selenocysteine is an essential component of the
enzyme glutathione peroxidase. This enzyme protects the
cells against the damage caused by H2O2. It appears from
recent studies that selenocysteine is directly incorporated
during protein biosynthesis. Therefore, selenocysteine is
considered as a separate amino acid.
Dietary Requirements
• A daily intake of 50-200mg of Se has been
recommended for adults.
• Sources:
• The good sources of Se are organ meats (liver, kidney)
and sea foods.
• Deficiency / Disease states:
• Deficiency: Se deficiency in animals leads to muscular
dystrophy, pancreatic fibrosis and reproductive
disorders. In humans, keshan disease, an endemic
cardiomyopathy (in china) is attributed to the
deficiency of Se. Epidemiological studies reveal that
low serum Se levels are associated with increased risk
of cardiovascular disease, and various cancers.
Chromium
• The total human body contains about 6mg chromium.
The Cr content of blood is about 20mg/dl.
• Biochemical functions:
• In association with insulin, Cr promotes the utilization
of glucose. Cr is a component of a protein namely
chromodulim which facilities the binding of insulin to
cell receptor sites.
• Cr lowers the total serum cholesterol level.
• It is involved in lipoprotein metabolism. Cr decreases
serum low density lipoproteins (LDL) and increases
high density lipoproteins (HDL) and, thus, promotes
health.
• It is believed that Cr participates in the transport of
amino acids into the cells (heart and liver)
Dietary requirements
• The dietary requirement of Cr is not known. It is
estimated that an adult man consumed about 10
to 100mg/day.
• Sources:
• The good sources of Cr include brewer’s yeast,
grains, cereals, cheese and meat.
• Deficiency /Disease states:
• Chromium deficiency causes disturbances in
carbohydrate, lipid and protein metabolisms.
Excessive intake of Cr results in toxicity, leading
to liver and kidney damage.
Ions
• Electrolytes are the compound which readily
dissociate in solution and exist as ions i.e. positively
and negatively charged particles.
• For instance, NaCl does not exist as such, but it exist
as cation (Na+) and anion (Cl-).
• The concentration of electrolytes are expressed as
milliequivalents (mEq/l) rather than milligrams.
• A gram equivalent weight of a compound is defined as
its weight in grams that can combine or displace 1g of
hydrogen. One gram equivalent weight is equivalent
to 1,000 milliequivalents.
• The following formula is employed to convert the
concentration mg/l to mEq/l
• mEq/l=
𝑚𝑔 𝑝𝑒𝑟 𝑙𝑖𝑡𝑟𝑒×𝑉𝑎𝑙𝑒𝑛𝑐𝑦
𝐴𝑡𝑜𝑚𝑖𝑐 𝑤𝑒𝑖𝑔ℎ𝑡
Electrolyte composition of body fluid
• Electrolytes are well distributed in the body
fluids in order to maintain the osmotic
equilibrium and water balance.
• A comparison of electrolytes present in
extracellular (plasma) and intracellular
(muscles) fluid is given in table below:
Extracellular fluid (plasma) Intracellular fluid (muscle)
Cations Anion Cations Anion
Na+ 142 Cl- 103 K+ 150 HPO2-
4 140
K+ 5 HCO-
3 27 Na+ 10 HCO-
3 10
Ca2+ 5 HPO 2-
4 2 Mg2+ 40 Cl- 2
Mg2+ 3 SO2-
4 1 Ca2+ 2 SO2-
4 5
Proteins 16 Proteins 40
6 Organic acids 5 Organic acids
155 155 202
202
Electrolyte composition of body fluid
• The total concentration of cations and anions in reach
in each body compartment (ECF or ICF) is equal to
maintain electrical neutrality .
• There is a marked difference in the concentration of
electrolytes (cations and anions) between the
extracellular and intracellular fluids.
• Na+ is the principle extracellular cation while K+ is the
intracellular cation.
• This difference in the concentration is essential for the
cell survival which is maintained by Na+ - K+ pump.
• As regards anions, Cl- and HCO-
3 predominantly occur
in extracellular fluids, while HPO-
4, proteins and
organic acids are found in the intracellular fluids.
Osmolarity and osmolality of body
fluid
• There are two ways of expressing the concentration
of molecules with regard to the osmotic pressure.
• Osmolarity: The number of moles (or millimoles)
per liter of solution.
• Osmolality: The number of moles ( or millimoles)
per kg of solvent.
• If the solvent is pure water, there is almost no
difference between osmolarity and osmolality.
However, for biological fluids (containing
molecules such as proteins), the osmolality is more
commonly used. This is about 6% greater than
osmolarity.
Osmolality of plasma
• Osmolality is a measure of the solute particles
present in the fluid medium. The osmolality of
plasma is in the range of 285-295 milliosmoles/kg.
Constituent (solute ) Osmolality (mosm/kg)
Sodium 135
Associated anions 135
Potassium 3.5
Associated anions 3.5
Calcium 1.5
Associated anions 1.5
Magnesium 1.0
Associated anions 1.0
Urea 5.0
Glucose 5.0
Protein 1.0
Total 293
Osmolality of ECF and ICF
• Movement of water across the biological
membranes is dependent on the osmotic pressure
differences between the intracellular fluid (ICF)
and extracellular fluid(ECF).
• In a healthy state, the osmotic pressure of ECF,
mainly due to Na+ ions, is equal to the osmotic
pressure of ICF which is predominantly due to K+
ions.
• As such, there is no net passage of water
molecules in or out of the cells, due to this
osmotic equilibrium.
Regulation of electrolyte balance
• Electrolyte and water balance are regulated together and the
kidneys play a predominant role in this regard. The regulation
is mostly achieved through the hormones aldosterone, ADH
and renin-angiotensin.
• Aldosterone: It is a mineralocorticoid produced by adrenal
cortex. Aldosterone increases Na+ reabsorption by the renal
tubules at the expense of K+ and H+ ions. The net effect is the
retention of Na+ in the body.
• Antidiuretic hormone (ADH): An increase in the plasma
osmolality (most due to Na+) stimulates hypothalamus to
release ADH, ADH effectively increases water reabsorption by
renal tubules.
• Renin-angiotensin: The secretion of aldosterone is controlled
by renin-angiotensin system. Decrease in the blood pressure
(due to a fall in ECF volume) is sensed by juxtaglomerular
apparatus of the nephron which secrete renin. Renin acts on
angiotensinogen to produce angiotensin I. The latter is then
converted to angiotensin II which stimulates the release of
aldosterone.
Regulation of electrolyte balance
• The relation between renin, angiotensin and aldosterone
in the regulation of Na+ balance is depicted in figure.
• Aldosterone and ADH coordinate with each other to
maintain the normal fluid and electrolyte balance.
• Atrial natriuretic factor (ANF): ANF or atriopeptin is a
28 amino acids containing peptide.
• It is produced in the atrium of heart in response to
increased blood volume, elevated blood pressure and
high salt intake.
• ANF acts on kidneys to increase GFR, sodium excretion
and urine output.
• Thus ANF opposes the actions of renin and aldosterone
(which increase salt retention and blood pressure).
Na+ concentration and ECF
• It is important to realize that Na+ and its anions
(mainly Cl-) are confined to the extracellular
fluid.
• And the retention of water in the ECF is directly
related to the osmotic effects of these ions (Na+
and Cl-).
• Therefore, the amount of Na+ in the ECF
ultimately determines its volume.
Dietary intake and electrolyte balance
• Generally, the consumption of a well-balanced diet
supplies the body requirement of electrolytes.
• Humans do not possess the ability to distinguish
between the salt hunger and water hunger.
• Thirst, however, may regulate electrolyte intake
also.
• In hot climates, the loss of electrolyte intake also.
• In hot climates, the loss of electrolyte is usually
higher.
• Sometimes it may be necessary to supplement
drinking water with electrolytes.
Dehydration
• Dehydration is a condition characterized by water
depletion in the body. It may be due to insufficient
intake or excessive water loss or both. Dehydration is
generally classified into two types.
• Due to loss of water alone.
• Due to deprivation of water and electrolytes.
• Causes of dehydration:
• Dehydration may occur as a result of diarrhea,
vomiting, excessive sweating, fluid loss in burns,
adrenocortical dysfunction, kidney diseases (e.g. renal
insufficiency), deficiency of ADH (diabetes insipidus)
etc.
Characteristics features of dehydration
• There are three degrees of dehydration mild,
moderate and severe. The salient features of
dehydration are given hereunder.
• The volume of the extracellular fluid (e.g. plasma)
is decreased with a concomitant rise in electrolyte
concentration and osmotic pressure.
• Water is drawn from the intracellular fluid that
result in shrunken cells and distributed metabolism
e.g. increased protein breakdown.
Characteristics features of dehydration
• ADH secretion is increased. This causes increased
water retention in the body and consequently urine
volume is very low.
• Plasma protein and blood urea concentrations are
increased.
• Water depletion is often accompanied by a loss of
electrolytes from the body (Na+, K+ etc.)
• The principal clinical symptoms of severe
dehydration include increased pulse rate, low blood
pressure, sunken eyeballs, decreased skin turgor,
lethargy, confusion and coma.
Treatment
• The treatment of choice for dehydration is intake
of plenty of water.
• In the subjects who cannot take orally, water
should be administered intravenously in an
isotonic solution (usually 5% glucose).
• If the dehydration is accompanied by loss of
electrolytes, the same should be administered by
oral or intravenous routes.
• This has to be done by carefully monitoring the
water and electrolyte status of the body
Osmotic imbalance and dehydration in
cholera
• Cholera is transmitted through water and foods,
contaminated by the bacterium vibrio cholerae.
• This bacterium produces a toxin which stimulates the
intestinal cells to secrete various ions (Cl-, Na+, K+, HCO-
3
etc.) into the intestinal lumen.
• These ions collectively raise the osmotic pressure and suck
the water into lumen.
• This results in diarrhea with a heavy loss of water (5-
10liters/ day).
• If not treated in time, the victims of cholera will die due to
dehydration and loss of dissolved salts.
• Thus, cholera and others forms of severe diarrhea are the
major killer of young children in many developing countries
• Oral redehydration therapy (ORT) is commonly used to treat
cholera and other diarrheal diseases.
Overhydration
• Overhydration or water intoxication is caused by
excessive retention of water in the body.
• This may occur due to excessive intake of large
volumes of salt free fluids, renal failure
overproduction of ADH etc.
• Overhydration is observed after major trauma or
operation, lung infections etc.
• Water intoxication is associated with dilution of
ECF and ICF with a decrease in osmolality.
• The clinical symptoms include headache, lethargy
and convulsions.
• The treatment advocated is stoppage of water intake
and administration of hypertonic saline.
Water tank model
• The distribution of body water (in the ECF and
ICF) dehydration and overhydration can be
better understood by a water tank model.
• The tank has an inlet and outlet, respectively,
representing the water intake (mostly oral) and
water output (mainly urine) by the body.
• Dehydration is caused when the water output
exceed the intake.
• One the other hand, overhydration is due to
more water intake and less output.
Metabolism of electrolytes
• The body distribution, dietary intake, intestinal absorption
and biochemical functions of individual electrolytes.
• The electrolyte disorders, particularly hypernatremia and
hyponatremia (of sodium); hyperkalemia and
hypokalemia (of potassium)must also be referred.
• Diuretics in the treatment of edema and hypertension:
• Diuretics are the drugs that stimulate water and sodium
excretion, so that urine volume is increased.
• The commonly used diuretics are bendrofluazide,
frusemide, spironolactone and mannitol.
• Diuretics are important in the treatment of edema, heart
failure and hypertension.
Water in life processes
• Water is the solvent of life. Undoubtedly, water is
more important than any other single compound to
life. It is involved in several body functions.
• Function of water:
• Water provides the aqueous medium to the
organism which is essential for the various
biochemical reactions to occur.
• Water directly participates as a reactant in several
metabolic reactions.
• It serves as a vehicle for transport of solutes.
• Water is closely associated with the regulation of
body temperature.
Distribution of water
• Water is the major body constituent. An adult human
contains about 60% water (men 55-70%, women 45-60%).
• The women and obese individuals have relatively less
water which is due to the higher content of stored fat in an
anhydrous form.
• A 70 kg normal man contains about 42 liters of water.
• This is distributed in intracellular (inside the cells 28l) and
extracellular (outside the cell 14l) compartments,
respectively known as intracellular fluid (ICF) and
extracellular fluid (ECF).
• The ECF is future divided into interstitial fluid (10.5l) and
plasma (3.5l).
• The distribution of water in man is given in table below:
Compartment % Body weight Volume (l)
Total 60 42
Intracellular fluid (ICF) 40 28
Extracellular fluid (ECF) 20 14
Interstitial fluid 15 10.5
Plasma 5 3.5
Water turnover and balance
• The body possesses tremendous capacity regulate its water
content. In a healthy individual, this is achieved by balancing the
daily water intake and water output.
• Water intake:
• Water is supplied to the body by exogenous and endogenous
sources
• Exogenous water: Ingested water and beverage, water content of
solid foods constitute the exogenous source of water.
• Water intake is highly variable which may range from 0.5-5 litres.
It largely depends on the social habits and climate.
• In general, people living in hot climate drink more water.
Ingestion of water is mainly controlled by a thirst centre located
in the hypothalamus.
• Increased in the osmolality of plasma causes increased water
intake by stimulating thirst centre.
Water turnover and balance
• Endogenous water: The metabolic water produce
within the body is the endogenous water.
• This water (300-350ml/day) is derived from the
oxidation of foodstuffs.
• It is estimated that 1g each of carbohydrate,
protein and fat, respectively, yield 0.6ml, 0.4ml
and 1.1ml of water.
• On an average, about 125ml of water is generated
for 1,000Cal consumed by the body.
Water output
• Water losses from the body are variable. There are four
distinct routes for the elimination of water the body-urine,
skin , lungs and feces.
• Urine:
• This is the major route for water loss from the body. In a
healthy individual, the urine output is about 1 -2l/day.
• Water loss through kidneys although highly variable, is well
regulated to meet the body demands-to get rid of water or to
retain.
• It should, however, be remembered that man cannot
completely shut down urine production, despite there being
no water intake.
• This is due to the fact that some amount of water (about
500ml/day) is essential as the medium to eliminate the waste
products from the body.
Hormonal regulation of urine production
• It is indeed surprising to know that about 180litres of water is
filtered by the glomeruli into the renal tubules everyday.
However, most of this is reabsorbed and only 1-2 litres is
excreted as urine. Water excretion by the kidney is tightly
controlled by vasopressin also known as antidiuretic hormone
(ADH) of the posterior pituitary gland. The secretion of ADH is
regulated by the osmotic pressure of plasma. An increase in
osmolality promotes ADH secretion that leads to an increased
water reabsorption from the renal tubules (less urine output).
On the other hand, a decrease in osmolality suppresses ADH
secretion that results in reduced water reabsorption from the
renal tubules (more urine output). Plasma osmolality is
largely dependent on the sodium concentration, hence
sodium indirectly controls the amount of water in the body.
• Diabetes insipidus is a disorder characterized by the
deficiency of ADH which results in an increased loss of water
from the body.
Skin
• Loss of water (450ml/day) occurs through the
body surface by perspiration.
• This is an unregulated process by the body
which mostly depends on the atmospheric
temperature and humidity.
• The loss is more in hot climate. Fever causes
increased water loss through the skin.
• It is estimated that for every 1ºC rise in body
temperature, about 15% increase is observed in
the loss of water (through skin).
Lungs
• During respiration, some amount of water (about
400ml/day) is lost through the expired air.
• The latter is saturated with water and expelled from
the body.
• In hot climates and / or when the person is suffering
from fever, the water loss through lungs is
increased.
• The loss of water by perspiration (via skin) and
respiration(via lungs) is collectively referred to as
insensible water loss.
Feces
• Most of the water entering the gastrointestinal
tract is reabsorbed by the intestine.
• About 150ml/day is lost through feces in a
healthy individual.
• Fecal loss of water is tremendously increased
in diarrhea.
• A summary of the water intake and output in
the body is depicted in below figure:
Body
water
42,000ml
Foodstuffs
(700ml)
Drinking water and
beverages (1,500ml)
Metabolic water (300ml)
Feces
(150 ml)
Lungs (400ml)
Skin(450ml)
Urine
(1,500ml)
Feces
• It may be noted that water balance of the body
is regulated predominantly by controlling the
urine output.
• This happens after an obligatory water loss via
skin, lungs and feces.
• The abnormalities associated with water
balance dehydration and over hydration will be
described, following a discussion on
electrolytes balance.

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Role of minerals, ions and water in.pptx

  • 1. Role of minerals, ions and water in life processes
  • 2. Minerals • The mineral (inorganic) elements constitute only a small proportion of the body weight. • There is a wide variation in their body content. For instance, calcium constitutes about 2% of body weight while cobalt about 0.00004%.
  • 3. General functions: • Mineral perform several vital functions which are absolutely essential for the very existence of the organism. • These include calcification of bone, blood coagulation, neuromuscular irritability, acid-base equilibrium, fluid balance and osmotic regulation. • Certain mineral are integral components of biologically important compounds such as hemoglobin (Fe), thyroxine (I), insulin(Zn) and vitamin B12(Co). • Sulfur is present in thiamine, biotin, lipoic acid and coenzyme A. • Several minerals participates as cofactors for enzymes in metabolism (e.g. Mg, Mn, Cu, Zn, K). • Some elements are essential constituents of certain enzymes (e.g. Co, Mo, Se)
  • 4. Classification • The minerals are classified as principal elements and trace elements. The seven principal elements (macro-minerals) constituents 60-80% of the body’s inorganic material. These are calcium, phosphorus, magnesium, sodium, potassium, chloride and sulfur. • The principal elements are required in amounts greater than 100 mg/day. The micro-minerals are required in amounts less 100mg/day. They are subdivided into three categories. • Essential trace elements : Iron, copper, iodine, manganese, zinc, molybdenum, cobalt, fluorine, selenium and chromium. • Possibly essential trace elements: Nickel, vanadium, cadmium and barium. • Non-essential trace elements: Aluminium, lead, mercury, boron, sliver, bismuth etc.
  • 5. Macro-elements • Calcium • Phosphorus • Magnesium • Sodium • Potassium • Chlorine • Sulfur
  • 6. Calcium • Calcium is the most abundant among the minerals in the body. • The total content of calcium in an adult man is about 1 to 1.5kg. As much as 99% of it is present in the bones and teeth. • A small fraction (1%) of the calcium, found outside the skeletal tissue, performs a wide variety of functions.
  • 7. Biochemical functions • Development of bones and teeth: Calcium, along with phosphate, is required for the formation (of hydroxyapatite) and physical strength of skeletal tissue. Bone is regarded as a mineralized connective tissue. Bones which are in dynamic state serve as reservoir of Ca. Osteoblasts result in demineralization. • Muscle contraction: Ca+ interacts with troponin C to trigger muscle contraction. Calcium also activates ATPase, increases the interaction between actin and myosin. • Blood coagulation: Several reactions in the cascade of blood clotting process are dependent on Ca+ (factor IV) • Nerve transmission: Ca+ is necessary for the transmission of nerve impulse. • Membrane integrity and permeability: Ca+ influences the membrane structure and transport of water and several ions across it.
  • 8. Biochemical functions • Activation of enzymes: Ca+ is needed for the direct activation of enzymes such as lipase (pancreatic), ATPase and succinate dehydrogenase. • Calmodulin mediated action of Ca2+: Calmodulin (mol. wt. 17,000) is a calcium binding regulatory protein. Ca- calmodulin complex activates certain enzymes e.g. adenylate cyclase, Ca2+ dependent protein kinase, myosin kinase, phospholipase C, glycogen synthase. • Calcium as intracellular messenger: Certain hormones exert their action through the mediation of Ca2+ (instead of cAMP). Calcium is regarded as a second messenger for such hormonal action e.g. epinephrine in liver glycogenolysis. Calcium serves as a third messenger for some hormones e.g. antidiuretic hormone (ADH) acts through cAMP, and then Ca2+.
  • 9. Biochemical functions • Release of hormones: The release of certain hormones (insulin, PTH, calcitonin) form the endocrine glands is facilitated by Ca2+. • Secretory processes: Ca2+ regulate microfilament and microtubule mediated processes such as endocytosis, exocytosis and cell motility. • Contact inhibition: Calcium is believed to be involved in cell to cell contact and adhesion of cells in a tissue. The cell to cell communication may also required Ca2+. • Action on heart: Ca2+ acts on myocardium and prolongs systole.
  • 10. Dietary requirements • Adult man and women – 800mg/day • Women during pregnancy, lactation , post- menopause – 1.5g/day Sources: • Best source –Milk and milk products • Good source – Beans, leafy vegetables, fish, cabbage, egg yolk.
  • 11.
  • 12. Deficiency/disease states • The blood Ca level is maintained within a narrow range by the homeostatic control, most predominantly by PTH. Hence abnormalities in Ca metabolism are mainly associates with alteration in PTH. • Hypercalcemia • Hypocalcemia
  • 13. Hypercalcemia • Elevation in serum Ca level (normal 9-11 mg/dl) is hypercalcemia. • Hypercalcemia is associated with hyperparathyroidism caused by increased activity of parathyroid glands. • Decreased in serum phosphate (due to increased renal loss) and increase in alkaline phosphate activity are also found in hyperparathyroidism. • Elevation in the urinary excretion of Ca and P, often resulting in the formation of urinary calculi, is also observed in these pateints.
  • 14. Hypercalcemia • The determination of ionized serum calcium (elevated or 6-9mg/dl) is more useful for the diagnosis of hyperparathyroidism. • It has been observed that some of the patients may have normal levels of total calcium in the serum but differ with regard to ionized calcium. • The symptoms of hypercalcemia include lethargy, muscle weakness, loss of appetite, constipation, nausea, increased myocardial contractility and susceptibility to fracture.
  • 15. Hypocalcemia • Hypocalcemia is a more serious and life threatening condition. It is characterized by a fall in the serum Ca to below 7mg/dl, causing tetany. • The symptoms of tetany include neuromuscular irritability, and convulsions. • Hypocalcemia is mostly due to hypoparathyroidism. This may happen after an accidental surgical removed of parathyroid glands or due to an autoimmune disease. • Treatment: Supplementation of oral calcium with vitamin D is commonly employed. In severe cases of hypocalcemia , calcium gluconate is intravenously administered.
  • 16. Rickets • Rickets is a disorder of defective calcification of bones. • This may be due to a low levels of vitamin D in the body or due to a dietary deficiency of Ca and P or both. • The concentration of serum Ca and P may be low or normal. • An increase in the activity of or normal. • An increase in the activity of alkaline phosphatase is a characteristic feature of rickets.
  • 17.
  • 18. Renal rickets • Renal rickets is associated with damage to renal tissue, causing impairment in the synthesis of calcitriol. • It does not respond to vitamin D in ordinary doses, therefore, some workers regard this as vitamin D resistant rickets. • Renal rickets can be treated by administration of calcitriol.
  • 19.
  • 20. Osteoporosis • Osteoporosis is characterized by demineralization of bone resulting in the progressive loss of bone mass. • Occurrence: The elderly people (over 60yr.) of both sexes are at risk for osteoporosis. However, it more predominantly occurs in the post- menopausal women. • Osteoporosis results in frequent bone fractures which are a major cause of disability among the elderly. • It is estimated that more than 50% of the fractures in USA are due to this disorder. Osteoporosis may be regarded as a silent thief.
  • 21.
  • 22. Treatment • Estrogen administration along with calcium supplementation (in combination with vitamin D) to postmenopausal women reduces the risk of fractures. • Higher dietary intake of Ca (about 1.5g/dl) is recommended for elderly people.
  • 23. Osteopetrosis (marble bone disease) • Osteopetrosis is characterized by increased bone density. • This is primarily due to inability to resorb bone. • This disorder is mostly observed is mostly observed in associated with renal tubular acidosis (due to a defects in the enzyme carbonic anhydrase)and cerebral calcification.
  • 24.
  • 25. Phosphorus • An adult body contains about 1kg phosphate and it is found in every cell of the body. • Most of it (about 80%) occurs in combination with Ca in the bones and teeth. • About 10% of body P is found in muscles and blood in association with proteins, carbohydrates and lipids. • The remaining 10% is widely distribution in various chemical compounds.
  • 26. Biochemical functions • Phosphorus is essential for the development of bones and teeth. • It plays a central role for the formation and utilization of high- energy phosphate compounds e.g. ATP, GTP, creatine phosphate etc. • Phosphorus is required for the formation of phospholipids, phosphoproteins and nucleic acids (DNA and RNA) • It is as essential component of several nucleotide coenzymes e.g. NAD+, NADP+, pyridoxal phosphate, ADP, AMP. • Several proteins and enzymes are activated by phosphorylation. • Phosphate buffer system is important for the maintenance of pH in the blood (around 7.4) as well as in the cells.
  • 27. Dietary requirement • The recommended dietary allowance (RDA) of phosphate is based on the intake of calcium. • The ratio of Ca: P of 1:1 is recommended (i.e. 800mg/day) for an adult. • For infants, however, the ratio is around 2:1, which is based on the ratio found in human milk. • Calcium and phosphate are distributed in the majority of nature foods in 1:1 ratio. • Therefore, adequate intake of Ca generally takes care of the P requirement also
  • 28. Sources • Milk, cereals, leafy vegetables, meat, eggs.
  • 29. Deficiency/disease states • Serum phosphate level is increased in hypoparathyroidism and decreased in hyperpara- thyroidism. • In severe renal diseases, serum phosphate content is elevated causing acidosis. • Vitamin D deficient rickets is characterized by decreased serum phosphate (1-2mg/dl). • Renal rickets is associated with low serum phosphate levels and increased alkaline phosphatase activity. • In diabetes mellitus, serum content of organic phosphate is lower while that of inorganic phosphate is higher.
  • 30. Magnesium • The adult body contains about 20 g magnesium, 70% of which is found in bones in combination with calcium and phosphorus. The remaining 30% occurs in the soft tissues and body fluid. • Biochemical functions: • Magnesium is required for the formation of bones and teeth. • Mg2+ serves as a cofactor for several enzymes requiring ATP e.g. hexokinase, glucokinase, phosphofructokinase, adenylatecyclase. • Mg2+is necessary for proper neuro-muscular function. Low Mg2+ levels lead to neuromuscular irritability.
  • 31.
  • 32. Dietary requirement • Adult man – 350mg/day • Adult women – 300mg/day • Sources: • Cereals, nuts, beans, vegetables (cabbage, cauliflower), meat, milk, fruits. • Deficiency/disease states: • Magnesium deficiency causes neuro-muscular irritation, weakness and convulsions. • These symptoms are similar to that observed in tetany (Ca deficiency) which are relieved only by Mg. Malnutrition, alcoholism and cirrhosis of liver may lead to Mg deficiency. • Low levels of Mg may be observed in uremia, rickets and abnormal pregnancy.
  • 33. Sodium • Sodium is the chief cation of the extracellular fluid. About 50% of body sodium is present in the bones, 40% in the extracellular fluid and the remaining (10%)in the soft tissues. • Biochemical functions: • In association with chloride and biocarbonate, sodium regulates the body’s acid-base balance. • Sodium is required for the maintenance of osmotic pressure and fluid balance. • It is necessary for the normal muscle irritability and cell permeability. • Sodium is involved in the intestinal absorption of glucose, galactose and amino acids. • It is necessary for initiating and maintaining heart beat.
  • 34. Dietary requirements • For normal individuals, the requirement of sodium is about 5-10 g/day which is mainly consumed as NaCl. • For persons with a family history of hypertension, the daily NaCl intake should be less than 5g. • For patients of hypertension, around 1g/day is recommended. • It may be noted that 10g of NaCl contains 4g of sodium. • The daily consumption of Na is generally higher than required due to its flavor
  • 35. Sources • The common salt (NaCl) used in the cooking medium is the cooking medium is the major source of sodium. • The ingested foods also contribute to sodium. • The good sources of sodium include bread, whole grains, leafy vegetables, nuts eggs and milk.
  • 36.
  • 37. Deficiency/disease states • Hyponatremia • This is a condition in which the serum sodium level falls below the normal. • Hyponatremia may occur due to diarrhea, vomiting, chronic renal diseases, adrenocortical insufficiency (Addison’s disease). • Administration of salt free fluids to patients may also cause hypoaremia. • This is due to overhydration. • Deceased serum sodium concentration is also observed in edema which occurs in cirrhosis or congestive heart failure. • The manifestations of hyponatremia include reduced blood pressure and circulatory failure.
  • 38. Hypernatremia • This condition is characterized by an elevation in the serum sodium level. • They symptoms include increase in blood volume and blood pressure. • It may occur due to hyperactivity of adrenal cortex (Cushing’s syndrome), prolonged administration of cortisone, ACTH and /or sex hormones. • Loss of water from the body causing dehydration, as it occurs in diabetes insipidus, results in hypernatremia. Rapid administration of sodium salts also increases serum sodium concentration. • It may be noted that in pregnancy, steroid and placental hormones cause sodium and water retention in the body, leading to edema. • In edema, along with water, sodium concentration in the body is also elevated. Administration of diuretic drugs increases the urinary output of water along with sodium. • In the patients of hypertension and congestive cardiac failure salt (Na+) restriction is advocated.
  • 39. Potassium • Potassium is the principal intracellular cation. It is equally important in the extracellular fluid for specific functions. • Biochemical functions: • Potassium maintains intracellular osmotic pressure. • It is required for the regulation of acid-base balance and water balance in the cells. • The enzyme pyruvate kinase (of glycolysis) is dependent on K+ for optimal activity. • Potassium is required for the transmission of nerve impulse. • Adequate intracellular concentration K+ is necessary for proper biosynthesis of proteins by ribosomes. • Extracellular K+ influence cardiac muscles activity.
  • 40. Dietary requirements • About 3-4 g/days • Sources: • Banana, orange , pineapple, potato, beans, chicken and liver. Tender coconut water is a rich source of potassium.
  • 41. Deficiency/disease states • Serum potassium concentration is maintained within a narrow range. Either high or low concentrations are dangerous since potassium effects the contractility of heart muscle. • Hypokalemia: Decreased in the concentration of serum potassium is observed due to overactivity of adrenal cortex (Cushing’s syndrome), prolonged cortisone therapy, intravenous administration of K+ free fluids, treatment of diabetic coma with insulin, prolonged diarrhea and vomiting. The symptoms of hypokalemia include irritability, muscular weakness, tachycardia , cardiomegaly and cardiac arrest. Changes in the ECG are observed (flattened waves with inverted T wave)
  • 42. Hyperkalemia • Increase in the concentration of serum potassium is observed in renal failure, adrenocortical insufficiency (Addison’s disease), diabetic coma, severe dehydration, intravenous administration of fluids with excessive potassium salts. • The manifestations of hyperkalemia include depression of central nervous system, mental confusion, numbness, bradycardia with reduced heart sounds and finally, cardiac arrest. Changes in ECG are also observed (elevated T wave).
  • 43. Chlorine • Chlorine is a constituent of sodium chloride. Hence, the metabolism of chlorine and sodium are intimately related. • Biochemical functions: • Chlorine is involved in the regulation of acid-base equilibrium, fluid balance and osmotic pressure. These functions are carried out by the interaction of chlorine with Na+ and K+. • Chlorine is necessary for the formation of HCL in the gastric juice. • Chlorine shift involved the active participation of Cl-. • The enzyme salivary amylase is activated by chloride.
  • 44. Dietary requirement • The daily requirement of chloride as NaCl is 5-10g. Adequate intake of sodium will satisfy the chloride requirement of the body. • Sources: • Common salt as cooking medium, whole grains, leafy vegetables, eggs and milk. • Deficiency/disease states: • Hypochloremia: A reduction in the serum Cl- level may occur due to vomiting, diarrhea, respiratory alkalosis, Addison’s disease and excessive sweating. • Hyperchloremia: An increase in serum Cl- concentration may be due to dehydration, respiratory acidosis and Cushing’s syndrome.
  • 45. Sulfur • Sulfur of the body is mostly present in the organic form. Meithionine, cysteine and cysteine are the three sulfur-containing amino acids present in the proteins. Generally, proteins contains about 1% sulfur by weight. • Biochemical functions: • Sulfur-containing amino acids are very essential for the structural conformation and biological functions of proteins (enzymes, hormones, structural proteins etc.). The disulfide linkages( -S – S-) and sulfhydryl groups (- SH) are largely responsible for this. • The vitamins thiamine, biotin, lipoic acid, and coenzyme A of pantothenic acid contain sulfur.
  • 46. Biochemical functions • Heparin, chondroitin sulfate, glutathione, taurocholic acid are some other important sulfur- containing compounds. • Phosphoadenosine phosphosulfate(PAPS) is the active sulfate utilized for several reactions e.g. synthesis of glycosaminoglycans, detoxification mechanism. • The sulfur-containing amino acid methionine (as S- adenosylmethionine) is actively involved in transmethylation reactions.
  • 47. Dietary requirements • Dietary requirements: • There is no specific dietary requirement for sulfur. • Sources: • Adequate intake of sulfur-containing essential amino acid methionine will meet the body need. Food proteins rich in methionine and cysteine are the sources of sulfur.
  • 48. Deficiency / disease states: • Sulfur is part of methionine and cysteine, which are amino acids needed in the making of proteins. So, if there is too little sulfur, or a sulfur deficiency, it could lead to reduced protein synthesis. • The sulfur-containing amino acid cysteine is also needed for making glutathione, which is somewhat of a superhero in body because it works as a potent antioxidant that protects cells from damage. So we see that a sulfur deficiency can cause a cascade of other problems. For instance, without sufficient sulfur to make cysteine, there could be reduced glutathione synthesis, which may contribute to cell damage
  • 49. Deficiency / disease states: • Sulfur is also needed to create connective tissues that support joints, such as cartilage, tendons and ligaments. • So, connection, have a deficiency of sulfur could contribute to joint pain or disease. • In fact, sulfur contained in medications designed for joint health.
  • 50. Micro-elements • Iron • Copper • Iodine • Manganese • Zinc • Molybdenum • Cobalt • Fluorine • Selenium • Chromium
  • 51. Iron • The total content of iron is an adult body id 3-5g. About 70% of this occurs in the erythrocytes of blood as a constituent of hemoglobin. • At least 5% of body iron is present in myoglobin of muscle. • Heme is the most predominant iron containing substance. • It is a constituent of several proteins/enzymes (hemoproteins)- hemoglobin, myoglobin, cytochromes, xanthine oxidase, catalase, tryptophan pyrrolase, peroxidase. • Certain other proteins contain non-heme ion e.g. transferrin, ferritin, hemosiderin.
  • 52. Biochemical functions • Iron mainly exerts its functions through the compounds in which it is present. Hemoglobin and myoglobin are required for the transport of O2 and CO2. • Cytochromes and certain non-heme proteins are necessary for electron transport chain and oxidative phosphorylation. • Peroxidase, the lysosomal enzyme, is required for phagocytosis and killing of bacteria by neutrophils. • Iron is associated with effective immuno- competence of the body.
  • 53. Dietary requirements • Adult man –10 mg/day • Menstruating woman – 18 mg/day • Sources: • Rich sources – Organ meats (liver, heat, kidney). • Good sources – Leafy vegetables, pulses, cereals, fish, apples, dried fruits, molasses, jaggery. • Poor sources – Milk, wheat, polished rice.
  • 54. Disease states • Iron deficiency anemia: :This is the most prevalent nutritional disorder worldover, including the well developed countries (e.g. USA). • Several factors may contribute to iron deficiency anemia. • These include inadequate intake or defective absorption of iron, chronic blood loss, repeated pregnancies and hookworm infections. • Strict vegetarian are more prone for iron deficiency anemia. This is due to the presence of inhibitors of iron absorption in the vegetarian foods, besides the relatively low content of iron. Iron deficiency anemia mostly occurs in growing children, adolescent girls, pregnant and lactating women. It is characterized by microcytic hypochromic anemia with reduced blood hemoglobin levels(<12g/dl). The other manifestation include apathy (dull and inactive), sluggish metabolic activities, related growth and loss of appetite. • Treatment: Iron deficiency is treated by supplementation of iron along with folic acid and vitamin C.
  • 55. Disease states • Hemosiderosis: • This is a less common disorder and is due to excessive iron in the body, frequently referred to as iron toxicity. • It is commonly observed in subjects receiving repeated blood transfusions over the years, e.g. patients of hemolytic anemia, hemophilia. • As already stated, iron is a one-way compound, once it enters the body, it cannot escapes. • Excessive iron is deposited as ferritin and hemosiderin. Hemosiderosis is commonly observed among the bantu tribe in south Africa. • This is attributed to a high intake of iron from their staple diet corn and their habit of cooking food in iron pots.
  • 56. Disease states • Hemochromatosis: This is a rate disease in which iron is directly deposited in the tissues (liver, spleen, pancreas and skin). • Hemosiderosis is sometimes accompanied by hemochromatosis. • Bronzed- pigmentation of the skin, cirrhosis of liver, pancreatic fibrosis are the manifestations of this disorder. • Hemochromatosis causes a condition known as bronze diabetes.
  • 57. Copper • The body contains about 100mg copper distributed in different organs. It is involved in several important functions. • Biochemical functions: • Copper is an essential constituent of several enzymes. These include cytochrome oxidase, catalase, tyrosine, superoxide dismutase, monoamine oxidase, ascorbic acid oxidase, ALA synthase, phenol oxidase and uricase. Due to its presence in a wide variety of enzymes, copper is involved in many metabolic reactions. • Copper is necessary for the synthesis of hemoglobin (Cu is a constituent of ALA synthase, needed for heme synthesis). • Lysyl oxidase ( a copper containing enzyme) is required for the conversion of certain lysine residues of collagen and elastin to allysine which are necessary for cross-linking these structural proteins.
  • 58. Biochemical functions • Ceruloplasmin serves as ferroxidase and is involved in the conversion of iron from Fe2+ to Fe3+ in which form iron (transferrin) is transported in plasma. • Copper is necessary for the synthesis of melanin and phospholipids. • Development of bone and nervous system (myelin) requires Cu. • Certain copper containing non-enzymatic proteins have been identified, although their functions are not clearly known. These include hepatocuprein (storage form in liver), cerebrocuprein (in brain) and hemocuprein (in RBC). • Hemocyanin, a copper protein complex in invertebrates, functions like hemoglobin for O2 transport.
  • 59. Dietary requirements • Adults – 2-3 mg/day • Infants and children – 0.5-2 mg/day • Sources: • Liver, kidney, meat, egg yolk, cereals, nuts and green leafy vegetables. Milk is a poor source.
  • 60. Deficiency /disease states • Copper deficiency: Several deficiency of copper causes demineralization of bones, demyelination of neural tissue, anemia, fragility of arteries, myocardial fibrosis, hypopigmentation of skin, greying of hair. • Menke’s disease: This disorder is due to a defect in the intestinal absorption of copper. It is possible that copper may be trapped by metallothionein in the intestinal cells. The symptoms of Menke’s disease include decreased copper in plasma and urine, anemia and depigmentation of hair.
  • 61. Deficiency /disease states • Wilson’s disease: Wilson’s disease (hepatolenticular degeneration) is a rare disorder (1:50,000) of abnormal copper metabolism and is characterized by the following manifestations. • Copper is deposited in abnormal amounts in liver and lenticular nucleus of brain. This may lead to hepatic cirrhosis and brain necrosis. • Low levels of copper and ceruloplasmin in plasma (reference range 20-50mg/dl) with increased excretion of copper in urine. • Copper deposition in kidney causes renal damage. This leads to increased excretion of amino acid, glucose, peptides and hemoglobin in urine. • Intestinal absorption of copper is very high, about 4-6 times higher than normal.
  • 62. Iodine • The total body contains about 20mg iodine most of it (80%) being present in the thyroid gland. Muscle, salivary glands and ovaries also contain some amount of iodine. • Biochemical functions: • The only known function of iodine is its requirement for the synthesis of thyroid hormones namely, thyroxine (T4) and trriodothyronine (T3). T3 is more active in its biological functions than T4.
  • 63. Biochemical functions • Influence on the metabolic rate: Thyroid hormones stimulate the metabolic activities and increases the oxygen consumption in most of the tissues of the body (exception- brain, lungs, testes and retina) • Effect on protein synthesis: Thyroid hormones act like steroid hormones in promoting protein synthesis by acting at the transcriptional level (activated DNA to produce RNA). Thyroid hormones, thus, function as anabolic hormones and cause positive nitrogen balance and promote growth and development.
  • 64. Biochemical functions • Influence on carbohydrate metabolism: Thyroid hormones promote intestinal absorption of glucose and its utilization. These hormones increase gluconeogenesis and glycogenolysis, with an overall effect of enhancing blood glucose level (hyperglycemia). • Effect on lipid metabolism: Lipid turnover and utilization are stimulated by thyroid hormones. Hypothyroidism is associated with elevated plasma cholesterol levels which can be reversed by thyroid hormone administration.
  • 65. Dietary requirements • Adults- 100-150µg/day • Pregnant women - 200µg/day • Sources: • Sea foods, drinking water, vegetables, fruits (grown on seaboard). High altitudes are deficient in iodine content in water as well as soil. Plant and animal foods of these areas, therefore, contain lesser amount of iodine. In these regions iodine is added to drinking water or table salt.
  • 66. Deficiency /disease states • Goiter: Any abnormal increase in the size of the thyroid gland is known as goiter. Enlargement of thyroid gland is mostly to compensate the deceased synthesis of thyroid hormones and is associated with elevated TSH. Goiter is primarily due to a failure in the auto regulation of T3and T4 synthesis. This may be caused by deficiency or excess of iodine. • Goitrogenic substances (goitrogens): These are the substances that interfere with the production of thyroid hormones. These include thiocyanates, nitrates and perchlorates and the drugs such as thiourea, thiouracil, thiocarbamide etc. certain plant foods – cabbage, cauliflower and turnip – contain goitrogenic factors (mostly thiocyanates).
  • 67. Deficiency /disease states • Simple endemic goiter: This is due to iodine deficiency in the diet. It is mostly found in the geographical regions away from sea coast where the water and soil are low in iodine content. Consumption of iodized salt is advocated to overcome the problem of endemic goiter. In certain cases, administration of thyroid hormone is also employed. • Hyperthyroidism: This is also known as thyrotoxicosis and is associated with over- production of thyroid hormones. Hyperthyroidism is characterized by increased metabolic rate (higher BMR) nervousness, irritability, anxiety, rapid heart rate, loss of weight despite increased appetite, weakness, diarrhea, sweating sensitivity to heart and often protrusion eyeballs (exophthalmos).
  • 68. Hyperthyroidism • Hyperthyroidism is caused by Grave’s disease (particularly in the developed countries) or due to increased intake of thyroid hormones. Grave’s disease is due to elevated thyroid stimulating IgG also known as long acting thyroid stimulator (LATS) which activates TSH and, thereby , increases thyroid hormonal production. • Hypothyroidism: This is due to an impairment in the function of thyroid gland that often causes decreased circulatory levels of T3 and T4. Disorder of pituitary or hypothalamus also contribute to hypothyroidism. Women are more susceptible than men. Hypothyroidism is characterized by reduced BMR, slow heart rate, weight gain, sluggish behaviour, constipation, sensitivity to cold, dry skin etc. Hypothyroidism in children is associated with physical and mental retardation, collectively known as cretinism.
  • 69. Manganese • The total body content of manganese is about 15mg. The liver and kidney are rich in Mn. Within the cells, Mn is mainly found in the nuclei in association with nucleic acids. • Biochemical functions: • Mn serve as a cofactor for several enzymes. These include arginase, pyruvate carboxylase, isocitrate dehydrogenase, superoxidase dismutase (mitrochondrial) peptidase. • Mn is required for the formation of bone, proper reproduction and normal functioning of nervous system.
  • 70. Biochemical functions • Mn is necessary for the synthesis of mucopolysaccharides and glycoproetins. • Hemoglobin synthesis involves Mn. • Mn inhibits lipid peroxidation. • Mn is necessary for cholesterol biosynthesis
  • 71. Dietary requirements • The exact requirement of Mn is not known. About 2- 9mg/day is recommended for an adult. • Sources: • Cereals, nuts ,leafy vegetables and fruits. Tea is rich sources of Mn.
  • 72. Deficiency/ disease states • Mn deficiency in animals causes: • Retarded growth, bone deformities and, in severe deficiency, sterility. • Accumulation of fat in liver. • Increased activity of serum alkaline phosphatase, and • Diminished activity of β- cells of pancreas (low insulin).
  • 73. Zinc • The total content of zinc in an adult blood is about 2g. Prostate gland is very rich in Zn (100mg/g). Zinc is mainly an intracellular element. • Biochemical functions: • Zn is an essential component of several enzymes e.g. carbonic anhydrase, alcohol dehydrogenase, alkaline phosphatase, carboxy-peptidase, superoxidase dismutase (cytosolic). • Zinc may be regarded as an antioxidant since the enzyme superoxide dismutase (Zn containing ) protects the body against free radicals damage.
  • 74. Biochemical functions • The storage and secretion of insulin form the β- cells of pancreas require Zn. • Zn is necessary to maintain the normal levels of vitamin A in serum. Zn promotes the synthesis of retinol binding protein. • It is required for wound healing . Zn enhances cell growth and division, besides stabilizing biomembranes. • Gusten, a zinc containing protein of the saliva, is important for taste sensation. • Zn is essential for proper reproduction.
  • 75. Dietary requirements • Zinc requirement for an adult is 10 -15 mg/day. It is increased (by about 50%) in pregnancy and lactation. • Sources: • Meat, fish, eggs, milk, beans, nuts.
  • 76. Deficiency / disease states • Zinc deficiency is associated with growth retardation, poor wound healing, anemia, loss of appetite , loss of taste sensation, impaired spermatogenesis etc. • It is reported that Zn deficiency in pregnant animals causes congenital malformations of the fetus. • Deficiency of Zn may result in depression, dementia and other psychiatric disorders. • The neuropsychiatric manifestations of chronic alcoholism may be partly due to zinc deficiency.
  • 77. Deficiency / disease states • Acrodermatitis enteropathica is a rare inherited metabolic disease of zinc deficiency caused by a defect in the absorption of Zn from, the intestine. • Zinc toxicity is often observed in welders due to inhalation of zinc oxide fumes. The manifestations of Zn toxicity include nausea, gastric ulcer, pancreatitis, anemia and excessive salivation.
  • 78. Molybdenum • Molybdenum is a constituent of the enzymes xanthine oxidase, aldehyde oxidase and sulfite oxidase. • Nitrite reductase (containing Mo)is a plant enzyme, required for nitrogen fixation. • The requirements of Mo are not clearly known. • However, it is widely distributed in the natural foods. Dietary Mo is effectively (60%-70%) absorbed by the small intestine. • Some workers have reported that Mo decreases the mobilization and utilization of copper in the body. • Molybdenosis is a rare disorder caused by excessive consumption of Mo. • Its manifestations include impairment in growth, diarrhea and anemia. • Intestinal absorption of copper is diminished.
  • 79. Biochemical functions • The molybdoenzymes in man are sulphite oxidase, xanthine oxidase/dehydrogenase and aldehyde oxidase. • The former is essential for detoxication of the sulphite arising from metabolism of sulphur- containing amino acids, from ingestion of bisulphite preservative and from inhalation of sulphur dioxide, an atmospheric pollutant. • The reactions catalysed by xanthine oxidase/dehydrogenase and aldehyde oxidase are necessary for human well-being has yet to be established
  • 80. Dietary requirements • Adult men and women is 109 and 76 μg/day • Sources: • Legumes, such as beans, lentils, and peas, are the richest sources of molybdenum. Grain products and nuts are considered good sources, while animal products, fruit, and many vegetables are generally low in molybdenum
  • 81. Deficiency /Disease states • The deficiency caused intellectual disability, seizures, opisthotonus, and lens dislocation. • Molybdenum deficiency resulting in sulfite toxicity occurred in a patient receiving long- term TPN (Total parenteral nutrition). • Symptoms were tachycardia, tachypnea, headache, nausea, vomiting, and coma
  • 82. Cobalt • Cobalt is only important as a constituent of vitamin B12 (cobalamin) cobalt content of vitamin B12 is about 4% by weight. • The functions of cobalt are the same as that of vitamin B12. • Administration of cobalt stimulates the production of the hormones erythropoietin, which promotes erythropoiesis. • Prolonged administration of cobalt is toxic as it results in polycythemia (increased RBC in blood).
  • 83. Biochemical functions • Cobalt is an essential trace element that is an integral part of vitamin B12, which is essential in the metabolism of folic acid and fatty acids. • Besides cobalt is involved in the production of red blood cells and is important for the proper functioning of the nervous system as it can help in creating a myelin sheath. • Dietary requirements: • The average adult intake of cobalt is 5–8 mcg per day. A safe Recommended Dietary Allowance (RDA) for cobalt hasn't been set yet.
  • 84. Sources • Meat, liver, kidneys, milk, oysters, muscles, fish, shellfish. Smaller amounts of cobalt are found in mushrooms (especially shitake). In fruits and vegetables, usually there are no cobalt (with the exception of legumes, spinach, cabbage, lettuce, turnips, cabbage, figs). • Deficiency /Disease states: • If you have a cobalt deficiency, this also means you have a vitamin B-12 deficiency. Anemia is a main cause of a cobalt deficiency. This is the case with pernicious anemia. Symptoms can include numbness, fatigue and tingling in hand and feet.
  • 85. Fluorine • Fluorine is mostly found in bones and teeth. The beneficial effects of fluoride in trace amounts are overshadowed by its harmful effects caused by excess consumption. • Biochemical functions: • Fluorine prevents the development of dental caries. It forms a protective layer of acid resistant fluoroapatite with hydroxyapatite of the enamel and prevents the tooth decay by bacterial acids. Further, inhibits the bacterial enzymes and reduces the production of acids. • Fluorine is necessary for the proper development of bones. • It inhibits the activities of certain enzymes. Sodium fluoride inhibits enolase (of glycolysis) while fluoroacetate inhibits aconitase (of citric acid cycle).
  • 86. Dietary requirements • An intake of less than 2 ppm of fluorine will meet the daily requirements. • Sources: • Drinking water is the main sources. • Deficiency/Disease states: • Dental caries: It is clearly established that drinking water containing less than 0.5ppm of fluoride is associated with the development of dental caries in children. • Fluorosis: Excessive intake of fluoride is harmful to the body. An intake above 2ppm (particularly >5ppm)in children causes mottling of enamel and discoloration of teeth. The teeth are weak and become rough with characteristic brown or yellow patches on their surface. These manifestations are collectively referred to as dental fluorosis.
  • 87. Selenium • Selenium was originally identified as an element that causes toxicity to animals (alkali disease) in some parts of USA, containing large amounts of Se in the soil. Later work, however, has shown that Se in smaller amounts is biologically important. • Biochemical functions: • Selenium, along with vitamin E, prevents the development of hepatic necrosis and muscular dystrophy. • Se is involved in maintaining structural integrity of biological membranes. • Se as selenocysteine is an essential component of the enzyme glutathione peroxidase. This enzyme protects the cells against the damage caused by H2O2. It appears from recent studies that selenocysteine is directly incorporated during protein biosynthesis. Therefore, selenocysteine is considered as a separate amino acid.
  • 88. Dietary Requirements • A daily intake of 50-200mg of Se has been recommended for adults. • Sources: • The good sources of Se are organ meats (liver, kidney) and sea foods. • Deficiency / Disease states: • Deficiency: Se deficiency in animals leads to muscular dystrophy, pancreatic fibrosis and reproductive disorders. In humans, keshan disease, an endemic cardiomyopathy (in china) is attributed to the deficiency of Se. Epidemiological studies reveal that low serum Se levels are associated with increased risk of cardiovascular disease, and various cancers.
  • 89. Chromium • The total human body contains about 6mg chromium. The Cr content of blood is about 20mg/dl. • Biochemical functions: • In association with insulin, Cr promotes the utilization of glucose. Cr is a component of a protein namely chromodulim which facilities the binding of insulin to cell receptor sites. • Cr lowers the total serum cholesterol level. • It is involved in lipoprotein metabolism. Cr decreases serum low density lipoproteins (LDL) and increases high density lipoproteins (HDL) and, thus, promotes health. • It is believed that Cr participates in the transport of amino acids into the cells (heart and liver)
  • 90. Dietary requirements • The dietary requirement of Cr is not known. It is estimated that an adult man consumed about 10 to 100mg/day. • Sources: • The good sources of Cr include brewer’s yeast, grains, cereals, cheese and meat. • Deficiency /Disease states: • Chromium deficiency causes disturbances in carbohydrate, lipid and protein metabolisms. Excessive intake of Cr results in toxicity, leading to liver and kidney damage.
  • 91. Ions • Electrolytes are the compound which readily dissociate in solution and exist as ions i.e. positively and negatively charged particles. • For instance, NaCl does not exist as such, but it exist as cation (Na+) and anion (Cl-). • The concentration of electrolytes are expressed as milliequivalents (mEq/l) rather than milligrams. • A gram equivalent weight of a compound is defined as its weight in grams that can combine or displace 1g of hydrogen. One gram equivalent weight is equivalent to 1,000 milliequivalents. • The following formula is employed to convert the concentration mg/l to mEq/l • mEq/l= 𝑚𝑔 𝑝𝑒𝑟 𝑙𝑖𝑡𝑟𝑒×𝑉𝑎𝑙𝑒𝑛𝑐𝑦 𝐴𝑡𝑜𝑚𝑖𝑐 𝑤𝑒𝑖𝑔ℎ𝑡
  • 92. Electrolyte composition of body fluid • Electrolytes are well distributed in the body fluids in order to maintain the osmotic equilibrium and water balance. • A comparison of electrolytes present in extracellular (plasma) and intracellular (muscles) fluid is given in table below:
  • 93. Extracellular fluid (plasma) Intracellular fluid (muscle) Cations Anion Cations Anion Na+ 142 Cl- 103 K+ 150 HPO2- 4 140 K+ 5 HCO- 3 27 Na+ 10 HCO- 3 10 Ca2+ 5 HPO 2- 4 2 Mg2+ 40 Cl- 2 Mg2+ 3 SO2- 4 1 Ca2+ 2 SO2- 4 5 Proteins 16 Proteins 40 6 Organic acids 5 Organic acids 155 155 202 202
  • 94. Electrolyte composition of body fluid • The total concentration of cations and anions in reach in each body compartment (ECF or ICF) is equal to maintain electrical neutrality . • There is a marked difference in the concentration of electrolytes (cations and anions) between the extracellular and intracellular fluids. • Na+ is the principle extracellular cation while K+ is the intracellular cation. • This difference in the concentration is essential for the cell survival which is maintained by Na+ - K+ pump. • As regards anions, Cl- and HCO- 3 predominantly occur in extracellular fluids, while HPO- 4, proteins and organic acids are found in the intracellular fluids.
  • 95. Osmolarity and osmolality of body fluid • There are two ways of expressing the concentration of molecules with regard to the osmotic pressure. • Osmolarity: The number of moles (or millimoles) per liter of solution. • Osmolality: The number of moles ( or millimoles) per kg of solvent. • If the solvent is pure water, there is almost no difference between osmolarity and osmolality. However, for biological fluids (containing molecules such as proteins), the osmolality is more commonly used. This is about 6% greater than osmolarity.
  • 96. Osmolality of plasma • Osmolality is a measure of the solute particles present in the fluid medium. The osmolality of plasma is in the range of 285-295 milliosmoles/kg. Constituent (solute ) Osmolality (mosm/kg) Sodium 135 Associated anions 135 Potassium 3.5 Associated anions 3.5 Calcium 1.5 Associated anions 1.5 Magnesium 1.0 Associated anions 1.0 Urea 5.0 Glucose 5.0 Protein 1.0 Total 293
  • 97. Osmolality of ECF and ICF • Movement of water across the biological membranes is dependent on the osmotic pressure differences between the intracellular fluid (ICF) and extracellular fluid(ECF). • In a healthy state, the osmotic pressure of ECF, mainly due to Na+ ions, is equal to the osmotic pressure of ICF which is predominantly due to K+ ions. • As such, there is no net passage of water molecules in or out of the cells, due to this osmotic equilibrium.
  • 98. Regulation of electrolyte balance • Electrolyte and water balance are regulated together and the kidneys play a predominant role in this regard. The regulation is mostly achieved through the hormones aldosterone, ADH and renin-angiotensin. • Aldosterone: It is a mineralocorticoid produced by adrenal cortex. Aldosterone increases Na+ reabsorption by the renal tubules at the expense of K+ and H+ ions. The net effect is the retention of Na+ in the body. • Antidiuretic hormone (ADH): An increase in the plasma osmolality (most due to Na+) stimulates hypothalamus to release ADH, ADH effectively increases water reabsorption by renal tubules. • Renin-angiotensin: The secretion of aldosterone is controlled by renin-angiotensin system. Decrease in the blood pressure (due to a fall in ECF volume) is sensed by juxtaglomerular apparatus of the nephron which secrete renin. Renin acts on angiotensinogen to produce angiotensin I. The latter is then converted to angiotensin II which stimulates the release of aldosterone.
  • 99. Regulation of electrolyte balance • The relation between renin, angiotensin and aldosterone in the regulation of Na+ balance is depicted in figure. • Aldosterone and ADH coordinate with each other to maintain the normal fluid and electrolyte balance. • Atrial natriuretic factor (ANF): ANF or atriopeptin is a 28 amino acids containing peptide. • It is produced in the atrium of heart in response to increased blood volume, elevated blood pressure and high salt intake. • ANF acts on kidneys to increase GFR, sodium excretion and urine output. • Thus ANF opposes the actions of renin and aldosterone (which increase salt retention and blood pressure).
  • 100.
  • 101. Na+ concentration and ECF • It is important to realize that Na+ and its anions (mainly Cl-) are confined to the extracellular fluid. • And the retention of water in the ECF is directly related to the osmotic effects of these ions (Na+ and Cl-). • Therefore, the amount of Na+ in the ECF ultimately determines its volume.
  • 102. Dietary intake and electrolyte balance • Generally, the consumption of a well-balanced diet supplies the body requirement of electrolytes. • Humans do not possess the ability to distinguish between the salt hunger and water hunger. • Thirst, however, may regulate electrolyte intake also. • In hot climates, the loss of electrolyte intake also. • In hot climates, the loss of electrolyte is usually higher. • Sometimes it may be necessary to supplement drinking water with electrolytes.
  • 103. Dehydration • Dehydration is a condition characterized by water depletion in the body. It may be due to insufficient intake or excessive water loss or both. Dehydration is generally classified into two types. • Due to loss of water alone. • Due to deprivation of water and electrolytes. • Causes of dehydration: • Dehydration may occur as a result of diarrhea, vomiting, excessive sweating, fluid loss in burns, adrenocortical dysfunction, kidney diseases (e.g. renal insufficiency), deficiency of ADH (diabetes insipidus) etc.
  • 104. Characteristics features of dehydration • There are three degrees of dehydration mild, moderate and severe. The salient features of dehydration are given hereunder. • The volume of the extracellular fluid (e.g. plasma) is decreased with a concomitant rise in electrolyte concentration and osmotic pressure. • Water is drawn from the intracellular fluid that result in shrunken cells and distributed metabolism e.g. increased protein breakdown.
  • 105. Characteristics features of dehydration • ADH secretion is increased. This causes increased water retention in the body and consequently urine volume is very low. • Plasma protein and blood urea concentrations are increased. • Water depletion is often accompanied by a loss of electrolytes from the body (Na+, K+ etc.) • The principal clinical symptoms of severe dehydration include increased pulse rate, low blood pressure, sunken eyeballs, decreased skin turgor, lethargy, confusion and coma.
  • 106. Treatment • The treatment of choice for dehydration is intake of plenty of water. • In the subjects who cannot take orally, water should be administered intravenously in an isotonic solution (usually 5% glucose). • If the dehydration is accompanied by loss of electrolytes, the same should be administered by oral or intravenous routes. • This has to be done by carefully monitoring the water and electrolyte status of the body
  • 107. Osmotic imbalance and dehydration in cholera • Cholera is transmitted through water and foods, contaminated by the bacterium vibrio cholerae. • This bacterium produces a toxin which stimulates the intestinal cells to secrete various ions (Cl-, Na+, K+, HCO- 3 etc.) into the intestinal lumen. • These ions collectively raise the osmotic pressure and suck the water into lumen. • This results in diarrhea with a heavy loss of water (5- 10liters/ day). • If not treated in time, the victims of cholera will die due to dehydration and loss of dissolved salts. • Thus, cholera and others forms of severe diarrhea are the major killer of young children in many developing countries • Oral redehydration therapy (ORT) is commonly used to treat cholera and other diarrheal diseases.
  • 108. Overhydration • Overhydration or water intoxication is caused by excessive retention of water in the body. • This may occur due to excessive intake of large volumes of salt free fluids, renal failure overproduction of ADH etc. • Overhydration is observed after major trauma or operation, lung infections etc. • Water intoxication is associated with dilution of ECF and ICF with a decrease in osmolality. • The clinical symptoms include headache, lethargy and convulsions. • The treatment advocated is stoppage of water intake and administration of hypertonic saline.
  • 109. Water tank model • The distribution of body water (in the ECF and ICF) dehydration and overhydration can be better understood by a water tank model. • The tank has an inlet and outlet, respectively, representing the water intake (mostly oral) and water output (mainly urine) by the body. • Dehydration is caused when the water output exceed the intake. • One the other hand, overhydration is due to more water intake and less output.
  • 110.
  • 111. Metabolism of electrolytes • The body distribution, dietary intake, intestinal absorption and biochemical functions of individual electrolytes. • The electrolyte disorders, particularly hypernatremia and hyponatremia (of sodium); hyperkalemia and hypokalemia (of potassium)must also be referred. • Diuretics in the treatment of edema and hypertension: • Diuretics are the drugs that stimulate water and sodium excretion, so that urine volume is increased. • The commonly used diuretics are bendrofluazide, frusemide, spironolactone and mannitol. • Diuretics are important in the treatment of edema, heart failure and hypertension.
  • 112. Water in life processes • Water is the solvent of life. Undoubtedly, water is more important than any other single compound to life. It is involved in several body functions. • Function of water: • Water provides the aqueous medium to the organism which is essential for the various biochemical reactions to occur. • Water directly participates as a reactant in several metabolic reactions. • It serves as a vehicle for transport of solutes. • Water is closely associated with the regulation of body temperature.
  • 113. Distribution of water • Water is the major body constituent. An adult human contains about 60% water (men 55-70%, women 45-60%). • The women and obese individuals have relatively less water which is due to the higher content of stored fat in an anhydrous form. • A 70 kg normal man contains about 42 liters of water. • This is distributed in intracellular (inside the cells 28l) and extracellular (outside the cell 14l) compartments, respectively known as intracellular fluid (ICF) and extracellular fluid (ECF). • The ECF is future divided into interstitial fluid (10.5l) and plasma (3.5l). • The distribution of water in man is given in table below:
  • 114. Compartment % Body weight Volume (l) Total 60 42 Intracellular fluid (ICF) 40 28 Extracellular fluid (ECF) 20 14 Interstitial fluid 15 10.5 Plasma 5 3.5
  • 115. Water turnover and balance • The body possesses tremendous capacity regulate its water content. In a healthy individual, this is achieved by balancing the daily water intake and water output. • Water intake: • Water is supplied to the body by exogenous and endogenous sources • Exogenous water: Ingested water and beverage, water content of solid foods constitute the exogenous source of water. • Water intake is highly variable which may range from 0.5-5 litres. It largely depends on the social habits and climate. • In general, people living in hot climate drink more water. Ingestion of water is mainly controlled by a thirst centre located in the hypothalamus. • Increased in the osmolality of plasma causes increased water intake by stimulating thirst centre.
  • 116. Water turnover and balance • Endogenous water: The metabolic water produce within the body is the endogenous water. • This water (300-350ml/day) is derived from the oxidation of foodstuffs. • It is estimated that 1g each of carbohydrate, protein and fat, respectively, yield 0.6ml, 0.4ml and 1.1ml of water. • On an average, about 125ml of water is generated for 1,000Cal consumed by the body.
  • 117. Water output • Water losses from the body are variable. There are four distinct routes for the elimination of water the body-urine, skin , lungs and feces. • Urine: • This is the major route for water loss from the body. In a healthy individual, the urine output is about 1 -2l/day. • Water loss through kidneys although highly variable, is well regulated to meet the body demands-to get rid of water or to retain. • It should, however, be remembered that man cannot completely shut down urine production, despite there being no water intake. • This is due to the fact that some amount of water (about 500ml/day) is essential as the medium to eliminate the waste products from the body.
  • 118. Hormonal regulation of urine production • It is indeed surprising to know that about 180litres of water is filtered by the glomeruli into the renal tubules everyday. However, most of this is reabsorbed and only 1-2 litres is excreted as urine. Water excretion by the kidney is tightly controlled by vasopressin also known as antidiuretic hormone (ADH) of the posterior pituitary gland. The secretion of ADH is regulated by the osmotic pressure of plasma. An increase in osmolality promotes ADH secretion that leads to an increased water reabsorption from the renal tubules (less urine output). On the other hand, a decrease in osmolality suppresses ADH secretion that results in reduced water reabsorption from the renal tubules (more urine output). Plasma osmolality is largely dependent on the sodium concentration, hence sodium indirectly controls the amount of water in the body. • Diabetes insipidus is a disorder characterized by the deficiency of ADH which results in an increased loss of water from the body.
  • 119. Skin • Loss of water (450ml/day) occurs through the body surface by perspiration. • This is an unregulated process by the body which mostly depends on the atmospheric temperature and humidity. • The loss is more in hot climate. Fever causes increased water loss through the skin. • It is estimated that for every 1ºC rise in body temperature, about 15% increase is observed in the loss of water (through skin).
  • 120. Lungs • During respiration, some amount of water (about 400ml/day) is lost through the expired air. • The latter is saturated with water and expelled from the body. • In hot climates and / or when the person is suffering from fever, the water loss through lungs is increased. • The loss of water by perspiration (via skin) and respiration(via lungs) is collectively referred to as insensible water loss.
  • 121. Feces • Most of the water entering the gastrointestinal tract is reabsorbed by the intestine. • About 150ml/day is lost through feces in a healthy individual. • Fecal loss of water is tremendously increased in diarrhea. • A summary of the water intake and output in the body is depicted in below figure:
  • 122. Body water 42,000ml Foodstuffs (700ml) Drinking water and beverages (1,500ml) Metabolic water (300ml) Feces (150 ml) Lungs (400ml) Skin(450ml) Urine (1,500ml)
  • 123. Feces • It may be noted that water balance of the body is regulated predominantly by controlling the urine output. • This happens after an obligatory water loss via skin, lungs and feces. • The abnormalities associated with water balance dehydration and over hydration will be described, following a discussion on electrolytes balance.