This is a lecture class presentation about the nutritional importance of different macromolecules of the food and nutrition card for the students of Medical Biochemistry.

1. Food & Nutrition, Vitamins
&
Minerals

2. Nutritional importance of
macromolecules
Carbohydrates

3. Dietary carbohydrates are the
chief source of energy
for metabolism
by the body.

4. They make up
more than half (60-70%) of the
total caloric requirement
in most human diets.

5. Dietary carbohydrates
1. Starch:
Rice, wheat , potato etc.
2. Sucrose:
Table sugar

6. 3. Lactose:
Milk
4. Dietary fibres

7. RDA of carbohydrates:
300 – 500 g/day in adult.
Minimum daily intake of
carbohydrates should be
more than 100 g/day
to avoid protein & fat catabolism
which may leads to
ketosis.

8. Nutritional importance of carbohydrates

9. 1. Carbohydrates are the major
dietary source of energy.
About 60-80% of the caloric
requirement is provided by
carbohydrate.

10. 2. It spares endogenous protein and
fat by preventing catabolism.
Protein is necessary for
growth and development of the
body.

11. The expenditure of protein for
caloric purpose
should be restricted to prevent
negative nitrogen balance
of the body.

12. Excessive catabolism of fat
leads to ketosis.

13. 3. It serves energy during
starvation ,
in between meals &
during exercise.

14. 4. Several vital organs –
Brain , RBC , renal medulla
utilize only carbohydrates
for energy.

15. 5. Supply energy for muscle contraction.
The muscle glycogen
provides lactic acid via glycolysis
is utilized for
contraction of muscle.

16. 6. Synthesis of pentoses.

17. 6. Synthesis of non essential amino
acids.

18. 7. Endogenous synthesis of fat from
glucose.
Over consumption of
carbohydrates
leads to the formation of
fat
that is stored in the
adipose tissue.

19. 8. Essential for complete oxidation of
fat.
Fatty acid oxidation
forms a common metabolite
acetyl CoA.

20. This acetyl CoA for its
complete oxidation to form
energy via TCA cycle,
reacts with oxaloacetate
that is derived from
carbohydrates.

22. 9. Non- digestible carbohydrates
improve gut motility ,
prevent constipation ,
reduce cholesterol & carbohydrate
absorption.

23. Dietary fibres

24. Dietary fibres are the
non-digestible carbohydrates
& lignin
present in plants
which undergo
partial fermentation in the colon &
totally excreted in the
faeces.

25. Foods rich in dietary fiber
Fruits, vegetables Wheat bran
& grains

26. Types of dietary fiber

27. Depending on the solubility –
1. Soluble dietary fibres :
These are not truly soluble,
but well dispersed in water &
usually well fermented.
e.g. Pectin, gum, cutins etc.

29. 2. Insoluble dietary fibres :
These are poorly dispersed
in water & usually not fermented.
e.g. Cellulose, hemicellulose, lignin etc.

31. Sources:
Whole grain cereals Legumes
Breads Potatoes
Fruits Isphagula husk
Vegetables

32. Daily requirements:
20 – 35 g/day

33. Importance of dietary fibers

34. 1. Reduces constipation & haemorrhoid
formation by softening stool.
2. Increases bowl motility , thus reduces
exposure of gut to carcinogens.

35. 3. Decreases absorption of dietary fat
& cholesterol thereby increases
faecal loss of cholesterol.

36. 4. Delays gastric emptying &
generates sensation of fullness
thereby promotes the
feeling of satiety without
consumption of excess calories .

37. 5. Reduces postprandial
blood glucose concentration,
thus reduces the risk of
diabetes mellitus.

38. 6. Reduces the body weight &
prevents the risk of obesity.

39. 7. Decreases the incidence of
diverticulosis,
colon cancer &
atherosclerosis.

40. Excess intake of dietary fiber may
cause –
1. Diarrhoea
2. Malabsorption
3. Flatulence