This document provides an overview of nutrition including: - Nutrition is the science of food and its relationship to health. It includes everything that happens to food from consumption to use in the body. - Nutrients include macronutrients like carbohydrates, fats, proteins and micronutrients like vitamins and minerals which are required in smaller amounts. - Nutrition contributes to wellness by preventing diseases. Nutrients are obtained from foods and provide energy for bodily functions. - Recommended dietary allowances provide guidelines for adequate intake of nutrients. A balanced diet contains variety of foods in proper proportions.

1. NUTRITION
MS. MEGHALATHA T S
ASSISTANT PROFESSOR
DEPARTMENT OF BIOCHEMISTRY

2. INTRODUCTION
• ‘Nutrition’‐ the science of food and its
relationship to health. Nutrition has been
defined as food at work in the body.
• Nutrition includes everything that happens to
food from the time it is eaten until it is used
for various functions in the body.

3. • Dietetics is the practical application of the
principles of nutrition; it includes the planning
of meals for the well and the sick.
• Adequate, optimum and good nutrition are
expressions used to indicate that the supply of
the essential nutrients is correct in amount
and proportion.

4. Why is Nutrition Important?
• Nutrition contributes to wellness.
Wellness: the absence of disease
Physical, emotional, and spiritual health
• Critical components of wellness:
 Nutrition
Physical activity
• Nutrition can prevent disease.
Nutrient deficiency diseases: scurvy, goitre, rickets

5. Nutrients
Organic and inorganic complexes contained in food.
The word nutrient or “food factor” is used for specific dietary constituents
such as proteins, vitamins and minerals.
They are broadly divided in to:
 Macronutrients:
 Proteins
 Fats
 Carbohydrates
 Micronutrients:
 Vitamins
 Minerals
 Water

6. What Are Nutrients?
• Macronutrients: nutrients required in
relatively large amounts.
Provide energy to our bodies
Carbohydrates, fats and oils, proteins
• Micronutrients: nutrients required in smaller
amounts.
Vitamins and minerals

7. Energy From Nutrients
• We measure energy in kilocalories (kcal).
• Kilocalorie: amount of energy required to raise
the temperature of 1g of water by 1oC.
• On food labels, “calorie” actually refers to
kilocalories.
• The calorific value : energy density of nutrients/
energy yield per unit weight of food.

8. Carbohydrates
• Primary source of fuel for the body, especially for
the brain.
• Provide 4 kcal per gram
• Carbohydrates are found in grains (wheat, rice),
vegetables, fruits, and legumes.
• How does the body processes dietary
carbohydrates?

9. Carbohydrates –dietary fiber
• Dietary fiber:- The unavailable or indigestible
carbohydrate in the diet.
• It improves bowel motility, prevents constipation,
decreases reabsorption of bile acids thus
lowering cholesterol level and improves glucose
tolerance.
• It provides a feeling of fullness without
consumption of excess calories.
• Green leafy vegetables are good source of fiber.

10. Fats and oils
• Fats and oils are composed of lipids,
molecules that are insoluble in water
• Provide 7 kcal per gram.
• An important energy source during rest or low
intensity exercise.
• Found in butter, margarine, vegetable oils.
• How does the body processes dietary fats?

11. Proteins
• Proteins are chains of amino acids.
• Proteins can supply 4 kcal of energy per gram, but
are not a primary energy source.
• Proteins are an important source of nitrogen.
• Proteins are important for
• Building cells and tissues, Maintaining bones,
Repairing damage, Regulating metabolism
• Protein sources include meats, dairy products,
seeds, nuts, and legumes.
• How does the body processes dietary proteins?

12. Vitamins
• Vitamins: organic molecules that assist in
regulating body processes.
• Vitamins are micronutrients that do not
supply energy to our bodies.
Fat-soluble vitamins: Vitamins A, D, E and K
Water-soluble vitamins: Vitamin C and the B
vitamins

13. Minerals
• Minerals: inorganic substances required for
body processes.
• Minerals include sodium, calcium, iron,
potassium, and magnesium.
• Minerals have many different functions such
as fluid regulation, bone structure, muscle
movement, and nerve functioning.

14. Water
• Water is a critical nutrient for health and
survival.
• Water is involved in many body processes:
– fluid balance nutrient transport
– nerve impulses removal of wastes
– muscle contractions, chemical reactions
– many, many more…

15. Recommended Dietary Allowances
or Intakes (RDA or RDI)
• The average daily intake level required to
meet the needs of 97 – 98% of people in a
particular category
• The RDA of a nutrient is the amount (of that
nutrient) sufficient for the maintenance of
health in nearly all people.

16. Recommended Dietary Allowances
• These are the estimates of nutrient intakes
which individuals in a population group need
to consume to ensure that the physiological
needs of all subjects in that population are
met.
• It is not used for defining the energy
requirement, as any excess of energy intake is
as undesirable as its inadequate intake. Hence
for defining the RDA of energy only the
average requirement is considered.

17. Balanced Diet
• The diet which contains variety of foods in
such quantities and proportions that the need
for energy, amino acids, vitamins, minerals,
fats, carbohydrates & other nutrients is
adequately met for maintaining health, vitality
and general well‐being and also make a small
provision for extra nutrient to withstand short
duration of leanness.

19. Respiratory quotient(RQ)
• It is defined as the ratio of volume of CO2 (L/g)
produced to the oxygen (L/g) consumed (during
oxidation of foodstuffs).
• RQ of
– Carbohydrate - 1
– Fats - 0.7
– Proteins - 0.8
• RQ falls when the utilization of fat increases
in relation to carbohydrates
like: in diabetes mellitus

20. Determination of RQ
• Done by open circuit method
• The subjects breaths in the atmospheric air of
known composition.
• The expired air is collected in a rubber bag or
spirometer.
• The volume of expired air, the O2 content &
CO2 content are measured.
• RQ is calculated by using the formula.
Volume of CO2 produced
RQ =
Volume of O2 used

21. Utilization of energy in normal person
Three process to meet fuel demand of the
body…….
• Basal metabolic rate(BMR)
• Specific dynamic action(SDA)
• Physical activity

22. Basal metabolic rate(BMR)
• It is the energy required by an awake
individual during complete physical and
mental rest.
• Minimum energy to maintain life or sustain
vital functions like working of heart,
circulation, brain function, respiration etc.
• The metabolic rate during sleep is less than
BMR

23. Measurement of BMR
• BMR is measured directly by the heat evolved,
or indirectly by the volume of oxygen
consumed & CO2 evolved per unit
• Prerequisite conditions:
Post-absorptive state
Mental & physical relaxation
Person is awake
Temperature maintained at 20-25°C
Supine position.

24. Measurement:
• The BMR is determined either by the
apparatus of Benedict & Roth (closed circuit
device) or by the Douglas bag method (open
circuit device).
• By Benedict-Roth method, the volume of O2
consumed (recorded on a graph paper) by the
subject for a period of 2-6 minutes under
basal conditions is determined.

25. Calculation of energy consumption
The energy consumed is calculated from oxygen
consumption.
The oxygen consumed per hour is multiplied by
constant 4.825 calories.
One litre of oxygen consumption is equivalent to
4.825 calories, when RQ of diet is 0.82.

26. • For the calculation of body surface area, the
simple formula by Du Bois and Du Bois is used.
• Body surface area =H0.725 x W0.425 x 71.84
A = H0.725 x W0.425 x 71.84
A = Surface area in cm2
H = Height in cm
W = Weight in kg.

27. Normal values
BMR is expressed as cal/sq.m/hr
• Adult males: 38 cal/sqm/hr
• Adult females: 33 cal/sqm/hr
The average body surface area for Indian
males is 1.62 sqm
For females = 1.4 sqm

28. Factors affecting BMR
• Surface area:
BMR is directly proportional to surface area.
Surface area is related to weight & height.
• Sex:
Men have higher (about 5%) BMR than women.
Due to the higher proportion of lean muscle mass
in men.
• Age:
In infants & growing children, with lean muscle
mass, the BMR is higher.
In adults, BMR decreases at the rate of about 20%
per decade of life.

29. • Physical activity:
BMR is increased in persons (athletes) with
regular exercise.
Due to increase in body surface area.
• Hormones:
Thyroid hormones (T3 & T4) have a
stimulatory effect on the metabolism of the body &
BMR.
Epinephrine, cortisol, growth hormone & sex
hormones increase BMR.

30. • Environment:
In cold climates, the BMR is higher
compared to warm climates.
• Starvation:
During the periods of starvation, the
energy intake has an inverse relation with
BMR, a decrease up to 50%

31. • Fever:
Fever causes an increase in BMR.
An elevation by more than 10% in BMR is
observed for every 1°C rise in body
temperature.
• Disease states:
BMR is elevated in various infections,
leukemias, polycythemia, cardiac failure, HTN.
In Addison's disease BMR is lowered

32. Significance of BMR
• BMR is important to calculate the calorie
requirement of an individual & planning of diets.
• Determination of BMR is useful for the
assessment of thyroid disorders.
• BMR is increased in thyrotoxicosis
(hyperthyroidism).
• BMR is decreased in hypothyroidism.

33. Specific dynamic action (SDA)
• The phenomenon of the extra heat production
by the body, over and above the calculated
caloric value, when a given food is metabolized
by the body, is known as specific dynamic action
(SDA).
• It is also known as calorigenic action or
thermogenic action or thermic action (effect) of
food.

34. SDA for different foods
SDA for different foods:
For a food containing 25 g of protein, the heat
production from the caloric value is 100 Cal
(25 x 4 Cal).
When 25 g protein is utilized by the body, 130
Cal of heat is liberated.
The extra 30 Cal is the SDA of protein.

35. SDA for protein, fat and carbohydrate 32%, 13% & 5%,
• Proteins possess the highest SDA while carbohydrates
have the lowest.
SDA for mixed diet:
• The presence of fats & carbohydrates reduces the SDA
of proteins.
• Fats are most efficient in reducing SDA of foodstuffs.
• For a regularly consumed mixed diet, the SDA is around
10%

36. Significance of SDA
• For the utilization of foods by the body,
certain amount of energy is consumed from
the body stores.
• Expenditure by the body for the utilization of
foodstuffs.
• It is the highest for proteins (30%) & lowest for
carbohydrates (5%) & for mixed diet 10%

37. • Additional 10% calories should be added to
the total energy needs (of the body) towards
SDA.
• The higher SDA for protein indicates that it is
not a good source of energy

38. Mechanism of SDA
• SDA of foods is due to the energy required for
digestion, absorption, transport, metabolism and
storage of foods in the body.
• The SDA of proteins is primarily to meet the
energy requirements for deamination, synthesis
of urea, biosynthesis of proteins, synthesis of
triacylglycerol (from carbon skeleton of amino
acids).

39. • Phenylalanine, glycine and alanine increase
the SDA.
• The SDA of carbohydrates is attributed to the
energy expenditure for the conversion of
glucose to glycogen.
• Fat, the SDA may be due to its storage,
mobilization and oxidation.

40. Consumption of protein rich diet cold climates:
• In cold climates, diet rich in proteins is
recommended, it helps to maintain the body
temperature.
• Due to its high SDA, liberates extra heat.

41. Physical activity
• The energy requirement depend on the
occupation, physical activity and lifestyle of
the individual.
Light worker (teachers, doctors) 30-40%BMR
Moderate worker (housewives, students) 40-50% BMR
Heavy work (labourers) 50-60% BMR
Very heavy work (workers & rickshaw
pullers)
60-100% BMR

42. Energy requirement of men
• Individual with light work about 60% of the
calories are spent towards BMR, about 30%
for physical activity & about 10% to take care
of the SDA.
Light work 2,200 – 2,500 Cal/day
Moderate work 2,500 – 2,900 Cal/day
Heavy work 2,900 – 3,500 Cal/day
Very heavy work 3,500 – 4,000 Cal/day

43. Environmental temperature
• Low temperature increases energy expenditure
by inducing shivering & non shivering
thermogenesis
• Shivering provides heat by increasing muscle
activity in response to cold stress.
• Non-shivering thermogenesis also produce heat.
• It is due to brown adipose tissue.
• It is stimulated by epinephrine &
norepinephrine.

44. Nitrogen balance
• Nitrogen balance: the dietary intake (I) equals the
daily loss through urine(U), Feces(F) and skin(S).
I=U+F+S
• Nitrogen intake occurs through proteins/AA
Negative nitrogen balance:- When excretion
exceeds intake
Positive nitrogen balance:- intake exceeds
excretion.
Nitrogen equilibrium: seen in normal individual
where intake equals excretion.

45. Factors affecting Nitrogen Balance
• Growth
• Hormones
• Pregnancy
• Convalescence
• Acute illness
• Chronic illness
• Protein deficiency

46. Assessment of nutritional values of
Proteins
• Protein efficiency ratio (PER)
• Biological Value(BV)
• Net protein utilization (NPU)
• Chemical score

47. Protein efficiency ratio (PER)
• PER is represented by gain in the weight of
rats per gram protein ingested
gain in body weight (g)
PER =
Protein ingested(g)

48. Biological Value(BV)
• BV is the percentage of absorbed nitrogen
retained by the body
nitrogen retained
BV = x 100
nitrogen absorbed

49. • Suppose 127 mg of protein “A” was consumed
by a rat in a day and 4 mg is recovered in feces
and 24 mg is seen in urine
then,
amount ingested =127mg
amount absorbed=127-4=123mg
amount retained= 123-24=99mg
therefore BV = 99/123x100=81%

50. Net protein utilization (NPU)
• NPU= retained nitrogen/intake of nitrogen x100
• NPU is better index than biological value, since it
takes into account the digestibility factor
Nitrogen retained
NPU= x100
Nitrogen ingested

51. Chemical score
• This is based on the chemical analysis of protein
for composition of essential amino acids which is
the compared with a reference protein(egg
protein)
• The chemical score is defined as the ratio
between the quality as the ratio between the
quantity of the most limiting essential amino
acid in the test protein to the quantity of the
same amino acid in egg protein.

52. Mg of limiting AA/g test protein
Chemical score= x100
Mg of same AA/g egg protein

53. Limiting amino acids
• When an essential amino acid is not provided in
adequate amounts in the diet, protein synthesis is
limited to the rate at which the essential amino
acid is available.
• Essential amino acids then become limiting
amino acids.
• The first-limiting amino acid is the essential
amino acid that first become deficient in the diet.
• Lysine is typically the first-limiting amino acid in
most swine diets because the requirement of
lysine is greater relative to the amount provided
in the diet.

54. Mutual supplementation of proteins
• It is fortunate that humans have the habit of
consuming mixed diet, with different foods,
simultaneously.
• Which helps to overcome the deficiency of certain
essential AA in one food being supplemented from
others.
• This phenomenon is mutual supplementation
• Eg: wheat protein(lysine-deficient, metionine rich) with
kidney bean protein (methionine- deficient, Lysine-rich)
• Results in a protein mixture of improved biological
value.

55. Mutual supplementation of proteins