This document provides an overview of nutrition and key nutrients. It discusses: - The main classes of nutrients including carbohydrates, proteins, lipids, vitamins, minerals and water. - How each nutrient is digested and absorbed. - The nutrient requirements and recommended daily intakes. - Energy balance and imbalances that can lead to obesity, marasmus or kwashiorkor. - Key aspects of water, electrolytes, trace elements, calcium and phosphorus including their functions, sources, regulation and imbalance issues.

1. NUTRITION-1
DR BAKER

2. Outline
• Introduction
• Nutrient needs
• Carbohydrates
• Proteins
• Lipids
• Vitamins and minerals
• Energy balance
• Obesity, Marasmus and Kwashiokor
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3. Intro
• Nutrition is the study of food including how it
nourishes our bodies and how it influences
our health.
• Nutrients are chemical in foods critical to
human growth and function.
• Classes of food???
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4. • Nutrients may be:
– Macronutrients: required in relatively large
amounts
– Micronutrients: nutrients needed in smaller
amounts
• Energy from nutrients are measured in
Kilocalories (Kcal):
– Amount of energy needed to raise the
temperature of water by 1ᵒC
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5. • Basal Metabolic Rate
– The energy expenditure by the body at rest, but not
asleep, under conditions of thermal neutrality,
measured about 12hrs after the last meal; and
depends on age, weight, gender and level of physical
activity
• Specific Dynamic Action
– Is the total increase in heat production which occurs
after the ingestion of a meal and which continues for
the entire period of subsequent metabolic processes.
– Factors that increase SDA?
– Factors that increase BMR?
– Which nutrients have the lowest and highest SDA’s?
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6. Nutrient Needs
• Each nutrient is needed in the body at a
certain amount daily.
• This is determined by the dietary reference
intakes this is in turn determined by four
values:
– Estimated Average Requirement which is the
average daily intake level of a nutrient that will
meet the needs of half the people in a particular
category. Is used to determine the RDA of a
nutrient.
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7. – Recommended Daily Allowance is the average daily
intake level of a nutrient required to meet the needs
of 97 -98% of people in a particular category.
– Adequate Intake is the recommended average daily
intake level for a nutrient; based on observations and
estimates from experiments and is used when the
RDA is not established.
– Tolerable Upper Intake Level is the highest average
daily intake level that is not likely to have adverse
effects on the health of most people; consumption of
nutrients above this level is not considered safe.
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8. • Also, in determining the nutrient needs;
– The Estimated Energy Requirement is the
average dietary energy intake (kcal) to maintain
energy balance based on weight, age, gender,
height and level of physical activity.
– The Acceptable Macronutrient Distribution
Ranges describes the portion of the energy intake
that should come from each macronutrient.
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9. Carbohydrates
• These are the primary source of fuel for the body;
especially the brain.
• Are broken down from poly-; oligo-; and disaccharides into
monosaccharides.
• This is done through hydrolysis
• By salivary and pancreatic amylases breaking the 1,4-
glycosidic bonds
• Disaccharidases: maltase, lactase, trehalase, sucrase-
isomaltase are present on brush border on intestinal cells.
Glycemic index?
The glycemic index, simply put, is a measure how quickly a food
causes our blood sugar levels to rise. The measure ranks food on a
scale of zero to 100. foods with a high glycemic index, or GI, are
quickly digested and absorbed, causing a rapid rise in blood sugar.
Lactose intolerance?
The inability to fully digest sugar (lactose) in dairy products. Lactose
intolerance is usually caused by a deficiency of an enzyme in the
body called lactase.
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10. Lipids
• These make up the fats and oils.
• They are mostly triglycerols and to a lesser
extent, phospholipids.
• They have to be hydrolysed into very small
droplets, micelles, before they can be
absorbed.
• Fat-soluble vitamins, ADEK, and cholesterol
are dissolved in these micelles.
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11. • Hydroysis is initiated by lingual and gastric lipases
which break the ester bond forming 1,2-diacyglycerols
and free fatty acids.
• Pancreatic lipase, breaks down the ester links at
positions 1 and 3
• Pancreatic esterase hydrolyses monoacyglycerols into
glycerols and fatty acids.
• Bile salts cause emulsification of these products into
micelles which become soluble and are then absorbed.
• The bile salts are reabsorbed through the
enterohepatic circulation.
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12. Proteins
• Important source of nitrogen
• The peptide bonds are cleaved by the
peptidases; which are of two types:
– Endopeptidase which hydrolyse peptide bonds
between specific amino acids throughout the
molecule;
• Are the first to act
• Yields larger number of smaller fragments
• E.g. Pepsin and trypsin
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13. – Exopeptidases which hydrolyses peptide bonds from
the ends of the peptides.
• One bond at a time
• Includes carboxypeptidases, aminopetidases,
dipeptidases and tripeptidases.
• These proteases are secreted as inactive
zymogens and are activated by hydrolysis of a
peptide bond.
– Pepsinogen to pepsin by gastric juice and activated
pepsin.
– Trypsinogen to trypsin by entropeptidase
– What enzyme activates chymotrypsinogen,
proelstase, proaminopeptidase and pro
carboxypeptidase? All the proenzymes in the
digestive tract, are activated by trypsin.
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14. • These free amino acids are the absorbed by
sodium-dependent transport.
• Some relatively large peptides are absorbed
intact and may be large enough to stimulate
antibody production.
• This forms the basis of allergic reaction to
foods.
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15. • Protein requirement is determined by
nitrogen balance
• This is the difference between intake and
output of nitrogenous substances.
• When intake equal output = equilibrium
• When intake is more than output = positive
balance
• When intake is less than output = negative
balance.
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16. Vitamins and Minerals
• These are released from foods during
digestion
• Fat-soluble vitamins are absorbed in micelles
• Water-soluble vitamins and most mineral salts
are absorbed by active transport or carrier-
mediated diffusion.
• This is usually followed by binding to
intracellular proteins to aid maximum uptake.
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17. Iron
• Iron absorption is limited about 10% of dietary
iron.
• Iron deficiency is a common cause of anemia
• It’s overload can also cause hemachromatosis
• Nonenzymatic generation of dangerous free
radicals by iron salts is limited by strictly
regulated absorption.
• Inorganic iron transported into the mucosal
cells by a divalent metal ion transporter.
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18. • This accumulates intracellularly and is bound to ferritin. (a
blood protein that contains iron.)
• It leaves these mucosal cells via transport protein –
ferroportin (is a transmembrane protein that transport
iron from the inside of the cell to the outside of the cell)
• It then binds to free transferrin in the plasma.
• Once saturated, and iron remaining in the mucosal cells are
lost when the cells are shed.
• Hepcidin is a peptide secreted by the liver when the iron
stores are adequate.
• This peptide downregulates ferroportin gene expression.
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19. • Hepcidin synthesis is reduced by hypoxia,
anaemia or haemorrhage.
• Iron is absorbed in its reduced state
• Thus reducing agents like vitamin C, alcohol and
fructose aid its absorption
how does calcium affect iron absorption?
Calcium (Ca) can inhibit iron (Fe) absorption,
regardless of whether it is given as Ca salt or in
dairy products. This has caused concern as
increased Ca intake commonly is recommended
for children and women, the same populations
that are at risk of Fe deficiency.
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20. Energy Balance
• The energy requirement of the body is
determined by the BMR
• Food eaten in excess of the energy
expenditure leads to = overnutrition: obesity
• When intake is lesser than expenditure =
undernutrition: emaciation, wasting,
marasus, kwashiokor.
• Both extremes are associated with increased
mortality.
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21. • The Body Mass Index is used to classify people into
nutritional categories
• This varies by race and gender
• Also has been found to be flawed in muscular people or
very tall and very short people.
• Most scholars suggest use of waist to hip ratio.
• These are used to determine risk for obesity and it’s
associated complications.
Familiarize yourself with the BMI chart (for negroes/africans)
and it’s formula.
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22. Waist to Hip ratio
Excellent Good Average At risk
Men <0.85 0.85 – 0.89 0.90 – 0.95 ≥0.95
Women <0.75 0.75 – 0.79 0.80 – 0.86 ≥0.86
• The measurements are done in cm
• The waist measurement is just above the belly button
at the line joining the top of the iliac crests
• The hip measurement is at the level of the greater
trochanters when the legs are closed together.
• Both measurements are done when standing upright!
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23. Obesity
• Is defined as abnormal or excessive fat
accumulation that presents a risk to health.
(WHO)
• A body mass index over 30 is regarded as obese.
• Has been on the increase and is one of the
burdens of malnutrition.
• Today, there are more obese people than
undernourished.
• Has risk of hypertension, diabetes, heart attacks,
stroke, kidney disease, joint disease etc
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24. Marasmus
• Is a syndrome of extreme malnutrition
• It occurs in both adults and children
• It a state of extreme emaciation.
• Outcome of prolonged negative balance
• There is exhaustion of body fat reserves and
muscle wasting.
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25. KWASHIOKOR
• Occurs only in children
• Reported only in developing countries
• Involves fluid retention and fatty infiltration of
the liver.
• Children have less stunted growth than marasmic
children.
• Infection usually precipitates kwashiokor
• There is also associated deficiency of zinc,
copper,, carotene, vitamin C and E.
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26. • Both marasmus and kwashiokor have:
– When it progresses there may be loss of protein
from heart, liver and kidneys.
– Amino acids released by catabolism is used as
fuel.
– Reduced immunity, reduction in absorption of
nutrients from GI.
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27. The difference between Marasmus
and kwashiokor
Kwashiorkor Marasmus
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Causes Deficiency of proteins Deficiency both proteins and
calories
Age factors Between the age of 6 months and
3 years of age.
Between the age of 6 months
and 1 year of age.
Oedema Present Absent
Subcutaneous
fat
Present Absent
Weight Loss There is some weight loss There is severe weight loss.

28. Nutrition-2
Water

29. OUTLINE
• Introduction
• Water and electrolytes
• Dehydration
• Trace elements
• Calcium
• Phosphorus

30. Intro
• Water is the predominant chemical
component in the living human body –
60%tbw.
• It has a dipolar structure and an exceptional
capacity for forming hydrogen bonds.
• It serves as a solvent for a wide range of
organic and inorganic molecules.

31. • Water is regulated by:
– Hypothalamic thirst mechanism
– Antidiuretic hormone – excretion and retention by the
kidneys
– Evaporative loss
• This is influenced by the osmolality of plasma and
blood volume.
• Water is distributed in the human body among
two compartments:
– Intracellular Fluid – 40%
– Extracellular fluids – 20%

32. • Water is maintained at a delicate balance in the
body
• Intake = Output
• In the tropics our lost in sweat, urine and faeces
• However, 200mL is gained from endogenous
metabolism of fat.
• Thus, net requirement a day is 3,200mL a day.
Water Loss volume (mL)
Pulmonary and cutaneous 1,700
Urine 1,500
Faeces 200
Total 3,400

33. Dehydration
• Is used to describe loss of water with
accompanying disruption of electrolyte balance.
• It may be rapid or gradual.
• For signs to show, at least 4% of body weight in
liters of water.
• It causes increased osmolality, which activates
osmoreceptors of the hypothalamus which
stimulates ADH production by the pituitary gland.

34. • Some symptoms of dehydration are:
– Dry mouth
– Inelastic skin with loss of turgor
– Tachycardia
– Scanty concentrated urine
– Sweating
– Collapsed veins
– Hypotension; then hypovolemic shock
• Is treated by drinking when mild and
rehydration with fluids that supply water and
lost electrolytes; when severe.

35. Water and electrolytes
• Electrolytes such as Na⁺; K⁺; Ca ²⁺; HCOᶟ⁻and
Cl⁻ are found dissolved in these fluids and also
determine the distribution of water across the
compartments.
• These electrolytes function mainly in
mediating membrane voltage change –
membrane potential
• This is most important in excitable tissues.

36. • These electrolytes can be lost or gained from or to the
body via:
– vomiting
– diarrhea
– excessive sweating
– Kidney disease
– Cell death
– Certain drugs
– Endocrine disease
• This leads to electrolyte imbalance which causes
symptoms of abnormal functioning of excitable tissues.

37. Trace elements
• These are minor elements due to the, having
very low plasma concentration.
• They are dietary elements.
• Serve as catalysts and cofactors in oxidation-
reduction reactions.
• They are needed for adequate growth and
development.

38. • Some are essential and others are not which
are toxic at even low concentrations e.g.
Arsenic, lead, nickel and cadmium.
• Essential ones include copper, manganese,
selenium, cobalt, zinc, flourine and iodine.
• Lack of these in diet could lead to chronic
illnesses.
• These are mostly gotten from water and other
foods.

39. Calcium
• Is necessary for life
• Functions in building bones, blood clotting
and muscle contractility.
• It is found in foods like: sardines, yogurt,
cheese, kale and salmon.
• Tolerable Upper Intake Levels for dietary and
supplemental calcium is 3g/day.
• Intra and extra cellular levels are tightly
regulated by the body.

40. • Vitamin D causes gastrointestinal absorption
of Calcium.
• This occurs via synthesis of calbindin –
calcium-binding protein.
• This can be inhibited by phytate and high
concentration of fatty acids which cause
chelation and formation of insoluble calcium
salts respectively.

41. • Vitamin D also causes reduction of kidney
excretion and mobilization of bone.
• Normal plasma levels is 2.2 – 2.6mmol/L
• Hypercalcemia cause deposition of salts in
kidneys, gall bladder, and blood vessels:
– Kidney stones
– Atherosclerosis
– Confusion
– Muscle weakness
– Bone pains
– nausea

42. • Hypocalcemia causes:
– Bone demineralisation
– Tetany
– Abnormal heart rhythm
• Abnormal values are caused by abnormal
parathyroid hormone levels and low vitamin
D.

43. Phosphorus
• This is a chemical element required for life
• Used to form ATP for phosphorylation and
phospholipids.
• Also exist in compounds making up bone and
teeth enamel.
• Food sources include: proteins, milk, meat and
soya.

44. • Vitamin D increases absorption form the GI
and increases excretion from kidneys.
• Abnormally low levels are caused by
malnutrition.
• Hypophosphatemia causes depletion of ATP –
dysfunction of brain, muscle and blood cells.
• Hyperphosphatemia leads to diarrhea

45. Thank you for your attention!!!