Chemistry of nutrition, Dietary principles of food, Basic energy consumption, Total calorie requirements, Energy providing foods, Nutrition balance, Body mass index

1. Dr. Subir Kumar Mandal
MBBS, M.Phil
Dietary Principles of
Food
..Food, Nutrition, Vitamins & Minerals..

3. Food, Growth & Development
 Food may be defined as any substance or
a composite mixture of various substances
that we eat for the purpose of maintenance,
growth and development of our body.
 Growth means a net increase in the size or
mass of tissues. It is due to multiplication of
cells and increase in the intracellular
substances.
 Development is defined as maturation of
functions.

4. Why do we need food?
 To satisfy hunger and appetite.
 To provide energy for the vital activities of
the body.
 To provide energy for different activities
of the body.
 For growth and development of body.
 To prevent deficiency diseases.
 Food stuff: Anything which can be used as
food.

6. Energy value of foods (Calorie)
 Energy value of foods is expressed in terms
of kcal or calorie (C). It is the amount of heat
required to raise the temperature of 1 gm of
H2O by [14.50C to 15.50C] 10
c.
 Energy means ability to do work or the
power which may be transmitted into motion,
effecting a physical change or overcoming
resistance.
 Calorimeter: An instrument for measuring
the amount of heat produced in any system
or organism.
1 calorie = 4.128 Joules.

7. Energy value of foods (continued)
Types of energy:
 Heat energy
 Free energy
 Kinetic energy
 Potential energy
 Chemical energy
 Electrical energy
 Nuclear energy
 Energy equivalent of food:
Carbohydrate-- 4.0 kcal/g
Protein-- 4.0 kcal/g
Fat-- 9.0 kcal/g

8. Energy balance
 Consumption of energy equal to energy
expended is called energy balance. 2 types-
 Positive energy balance: If the caloric value
of food content exceeds energy loss due to
heat, BMR and work and the food is properly
digested and absorbed, the balance is positive.
In this case energy is stored and the individual
gains weight.
 Negative energy balance: If the caloric
content of the food ingested is less than the
energy output, the balance is negative. In this
case endogenous stores are utilized. Glycogen,
body proteins and fats are catabolized and the
individual loses weight.

9. Utilization of energy in adult
The energy generated by metabolism of the
macronutrients is used for three energy-
requiring processes that occur in the body.
1) Basal/Resting metabolic rate (BMR/RMR)
2) Specific dynamic action (SDA)
3) Physical activity:
 For light activity: 25-50% BMR is added.
 For moderate activity: 50-100% BMR added
 For heavy activity: >100% BMR is added.

10. Basal metabolic rate/RMR
 The energy expended by an individual in a
resting, post absorptive state is called the
basal or resting metabolic rate.
 It represents the energy required to carry
out the normal body functions, such as
respiration, blood flow, muscle tone, ion
transport and maintenance of cellular integrity.
 Normal value of BMR in an adult male is
2000 kcal/day & in adult female is 1600
kcal/day.

11. Basal metabolic rate
Basal Conditions
 12 hours fasting.
 Overnight sound sleep.
 Complete mental & physical rest.
 Comfortable environmental temperature &
pressure.
 Awake.

12. Factors affecting BMR
1. Age: Higher in younger age.
2. Sex: Higher in male.
3. Thyroid hormone: Increase BMR.
4. Growth hormone: Increase BMR.
5. Fever, infection increases metabolic rate.
6. Sleep decreases metabolic rate.
7. Nutritional status: Decrease in starvation.
8. Climate: BMR increases in cold climate.
9. Pregnancy & lactation increases BMR.

13. Specific dynamic action (SDA)
 SDA is defined as the extra heat production
over & above the actual calorie value of a
given food when the food is metabolized with
in the body.
 It is regarded as the Calorigenic action of
food or the diet induced thermogenesis.
 The production of heat by the body
increases as much as thirty per cent above the
resting level during digestion and absorption
of food. This effect of food is called the
thermic effect of food. It may last up to 6
hours after meals.

14. SDA or Thermic effect of food
 The thermic effect
of food is due to
obligatory energy
expenditure that
occurs during
assimilation into the
body. It is 30% for
protein, 6% for
carbohydrate, 4% for
fat & 10% for mixed
diet.

15. Causes of thermic effect of food
 The exact cause of SDA is unknown.
 It may occurs due to increased sympathetic
discharge after feeding due to increased
catecholamine secretion.
 SDA of protein is due to deamination of the
amino acids in the liver after their absorption.
 SDA of carbohydrate is due to the energy
expenditure for the conversion of glucose to
glycogen.
 SDA of fat may be due to its storage,
mobilization & oxidation [direct stimulation of
metabolism by liberated fatty acids].

16. Why protein has the highest SDA?
Why a gram of fat gives about twice as m
uch calories as by same amount of CHO?
The chemical reaction for the breakdown of
proteins during digestion is more than
carbohydrates and fats.
 Some of the amino acids directly stimulate
the metabolic rate.
 The number of carbon in fat is more
(usually 16-20 C) than CHO (3-10 C). So, to
breakdown fat, more oxidation is occurred &
more energy is liberated than CHO.

17. Significance of SDA
1. The SDA of food must be considered in
calculating the total number for calorie
required for an individual.
2. The higher SDA of protein indicates that it
is not a good source of energy.
3. Fat is the best source of energy due to its
low SDA.
4. Due to high SDA, protein rich food makes
us feel warm in cold weather.

18. Physical activity
 Physical activity of an individual provides
the greatest variation in energy expenditure.
 The amount of energy consumed depends
on the duration and intensity of exercise.
 The daily expenditure of energy can be
estimated by carefully recording the type and
duration of all activities.

19. Basic calculation of energy requi
rement
 Actual requirement:
BMR+25% BMR [sedentary worker]
It is the summation of energy equivalent of
BMR & physical activity.
 Recommended requirement:
It is the actual requirement+10% of the
actual requirement. Here 10% stands for
SDA.
 For sedentary worker
Actual: BMR+25% BMR=2000+500=2500
Recommended: 2500+250= 2750 kcal/day.

20. Respiratory quotient
 The ratio of carbon dioxide production
and oxygen consumption is called respiratory
quotient (RQ).
 Use of respiratory quotient to determine
the relative utilization of different foods by
the body.
 RQ of Carbohydrate is 1, Protein is 0.8 &
Fat is 0.7.
Volume of CO2 produced
 RQ=
Volume of O2 consumed

21. Basic components of food
 Carbohydrate
 Protein
 Fat
 Vitamins
 Minerals
 Water
 Dietary fibers

22. Classification of food
Foods are classified on the basis of their
predominant functions:
1. Energy yielding food
Carbohydrate, fat (Rice, wheat, potato, sugar,
milk, cooking oil, fish, meat).
2. Body building food
Those foods which are rich in protein are
called body building foods (Meat, fish, milk,
egg, pulses)
3. Protective food
Foods which are rich in vitamins and minerals
(Fish, milk, meat, egg, liver, green leafy
vegetables and fruits).

24. Classification of food
Another way of food classification:
1. Calorigenic food: Gives energy.
2. Noncalorigenic food: Gives no energy, but
essential for energy yielding chemical
reactions in the body (vitamins and minerals).

25. Proximate principles of food:
o Carbohydrate
o Fat
o Protein
o Vitamins
o Minerals
o Water
o Fiber

26. Nutrition & Nutrients
 Nutrition may be defined as the process of
ingestion, digestion, absorption,
transportation, utilization of nutrients and
disposal of its end products.
 Nutrients are constituents of food that
must be supplied in suitable proportion and
amount to maintain health. It includes
carbohydrate, protein, fat, vitamins, minerals,
water and fibers.
 Essential nutrients are nutrients required
for normal functioning of the body that either
can’t be synthesized by the body at all or
can't be synthesized in amounts adequate for
good health, so must be obtained from
dietary sources.

27. Criteria/Indices of good nutrition
 It will protect the body from infection &
deficiency diseases.
 It will help in making a fair complexion e.g.
clean skin, bright eyes, lustrous hair & protect
from obesity.
 It will nourish the body & make the person
energetic.

28. Aims & signs of good nutrition
 Aims:
To meet up the caloric demand of the
individual needed for optimum physiological
functions.
 To meet up the specific requirements of the
individual items of food stuff.
 To formulate & plan diet in relation to
availability, cost, portability & social habits.
 Signs:
 Smooth & shiny skin.
 Glossy hair.
 Well developed muscles, bone & teeth.
 Strong built & energetic to look at.

29. DRIs- Dietary Reference Intakes
 It estimates of the amounts of nutrients
required to prevent deficiencies and maintain
optimal health. The DRIs consist of 4 (four)
dietary reference standards.
 Estimated Average Requirement (EAR):
It is the average daily nutrient intake level
estimated to meet the requirement of one
half the healthy individuals in a particular
life stage and gender group.
 The Recommended Dietary Allowance
(RDA): It represents the quantities of the
nutrients to be provided in diet daily for
maintaining good health & physical
efficiency of the body.

30. DRIs- Dietary Reference Intakes
 Adequate Intake (AI):
The AI is based on estimates of nutrient
intake by a group of apparently healthy
people that are assumed to be adequate.
 Tolerable Upper Intake Level (UL):
UL is the highest average daily nutrient intake
level that is likely to have no risk of adverse
health effects to almost all individuals in the
general population.

31. Recommended Daily Allowance
 R.D.A. is the amount of a nutrient that
should be taken by a person to maintain good
health. The amount of nutrients differ from
person to person depending on age, sex,
height, weight, life-style, etc.
 RDI (Reference Daily Intake or
Recommended Daily Intake) is another term
used almost synonymously.

32. RDA of Macronutrients
Macronutrients
Percentage of
total calorie that
should be met
RDA
Digestible
carbohydrates
55% 300-500 g/day
Digestible fats 30% 50-100 g/day
Digestible
proteins
15% 70-100 g/day

33. RDA of Vitamins
Vitamins RDA Vitamins RDA
Vitamin A (Adult)
Vitamin A (Preg.)
Vitamin A (Child)
Vitamin D
Vitamin E
Vitamin K
Vitamin C
5000 IU
6000 IU
3000 IU
400 IU
15 mg
120 mg
90 mg
Thiamin
Riboflavin
Niacin
Vit-B5
Vit-B6
Biotin
Folate
Vit-B12
1.2 mg
1.3 mg
16 mg
5 mg
1.3 mg
30 mg
400 mg
2.4 mg

34. RDA: Minerals
Macrominera
ls
RDA Micromineral
s
RDA
Sodium
Chloride
Potassium
Calcium
Magnesium
Phosphate
Iodine
1.5 g
2.3 g
4.7 g
1.0 g
400 mg
700 mg
150 mg
Iron (male)
Iron (female)
Preg/lactation
Zinc
Fluoride
Selenium
Chromium
Manganese
Copper
10 mg
18 mg
40 mg
11 mg
4 mg
55 mg
35 mg
2.3 mg
1 mg

35. Minimum daily requirement (MDR)
 It is the smallest amount of a nutrient that
is to be consumed to prevent its deficiency
symptoms.
Metabolic rate (MR)
 Metabolic rate is the energy liberated per
unit of time and it is 1.2 kcal/min at rest in
standard temperature & pressure.
 Some factors--BMR, SDA, Level of activity
& ingestion of food, Temperature, Emotional
state, Pregnancy and Lactation directly
influence metabolic rate.

36. Body Mass Index (BMI)
 BMI stands for Body Mass Index. BMI is a
measure to compare body weight to height.
It is calculated by the following simple
formula.
Weight in Kg
BMI =
(Height in meter)2
 1 feet = 30.48 cm.
 1 inch = 2.54 cm.

37. Body Mass Index (BMI)
 BMI is used for deciding whether people
have a healthy weight for their height and for
predicting the likelihood of the cardiovascular
diseases, diabetes etc.
 Obesity is gradually increasing globally.
Particularly alarming is the explosion of
childhood obesity. By some estimates, the
number of overweight and obese people in
the world is greater than the number who
lack sufficient food.
 Approximately 65% of adults in the United
States are overweight and nearly 33% of
adults are obese.

38. Body Mass Index (BMI)
BMI Physical condition
<18.5 Under nutrition
18.5 – 24.9 Healthy/Normal
25.0 – 29.9 Overweight
≥ 30.0 Obese
> 40 Extreme obese

39. Essential Nutrients
 Carbohydrate
 Protein (Essential amino acids)
 Fat (Essential fatty acids)
 Vitamins
 Minerals
 Water
 Fibers

40. Essential Nutrients

41. Non-essential Nutrients
 The nutrients which body can synthesize
and required for normal body functions but
their presence in diet is not essential.
e.g. Non essential amino acids, non essential
fatty acids.

42. Nutrients continued
Based on daily requirements:
 Macronutrients:
The nutrients that are required in larger
quantity (several grams) are called the major
or macronutrients i.e. Carbohydrate, Protein,
Fat, Macrominerals.
 Micronutrients:
The nutrients that are required in lesser
amounts (µg/mg) are called the minor or
micronutrients i.e. Vitamins, Microminerals.

43. Diet, Balanced diet
 Diet: Is a designed calculated amount of
food for an individual in a particular state of
body. Example: Diet for a pregnant woman.
 Balanced diet: Diet containing all the
nutritive factors in proper proportion for
adequate nutrition for an individual in a
particular state of body.

45. Balanced diet

46. Factors to be considered to
formulate a diet/balanced diet
1. Age
2. Sex
3. Occupation
4. Environment
5. Food habit and digestibility
6. Biological value of food
7. Economic condition
8. Religion
9. Social customs

47. Planning of balanced diet
1. Energy calculation
a) Basic energy needs (BMR+Physical activity)
b) Recommended energy needs (basic energy
need + 10% for SDA)
2. Distribution of energy to different foods
a) 60% ascribed to CHO.
b) 30% ascribed to fat.
c) 10% ascribed to protein.
3. Selection of food according to the
availability & economic status.
4. Inclusion of fibers & adequate fruits &
vegetables.

48. Criteria of a balanced diet
 Easily available.
 Sufficient to satisfy taste & appetite.
 Should be palatable.
 Should be easily digestible, absorbable &
assimiable.
 Should contain sufficient vegetables & fruits
 Vitamins & minerals should be present in
sufficient quantity,
 Ratio of carbohydrate, protein & fat must
be 4:1:1 [CHO- 400gm, Protein-100gm, Fat-100
gm].

49. Criteria of suitable diet
 It must be capable of digestion, absorption
& assimilation.
 It must be palatable.
 It must contain sufficient protein to provide
for growth, waste & repair.
 It must supply sufficient energy.
 It must have sufficient amount of fat, CHO,
water & salts in suitable proportion.
 It must contain vitamins.

50. Effects of cooking on diet
1) Inedible portions are removed.
2) Harmful bacteria & organisms are
destroyed.
3) Collagen fibers of meat are converted to
gelatin for easy digestion.
4) It increases taste & flavor of the food by
which salivary secretion containing salivary
α-amylase is increased.
5) It increases the water content &
digestibility of vegetables.
6) Fats are little changed in the process of
cooking.
7) Vitamin-B1 & Vit-C are specially destroyed
on cooking.