Dietary components and their functions -Food and energy, caloric and protein value, manifestations of deficiency in calories

Ayurveda for a healthy life ! – 42/2024 on 16.12.2024

CALORIES

1.  How does food supply energy ?

On burning wood in the presence of oxygen, one gets energy in the form of light and heat. Similarly, energy is produced in the body by oxidation of food. Oxygen from air obtained by breathing combines with the food particles, i.e. carbohydrates, fats and proteins in the cells of the body. This process leads to a slow burning of the food particles and releases energy. This energy is measured in terms of calories.

2.  What is a calorie in the context of food ? How does food supply energy to sustain all the body’s activities ?

For the sake of convenience and ease, the energy derived from food is calculated in the unit of heat energy, i.e. calorie. One calorie is the amount of heat required to raise the temperature of 1 ml. of water from 14.5^oC to 15.5^oC, i.e. by 1^oC. A kilocalorie is the amount of heat required to raise the temperature of 1 litre of water from 14.5^oC to 15.5^oC, i.e. by 1^oC.

As the energy requirements of the body and food values are always calculated in terms of kilocalories, the prefix ‘kilo’ is often omitted in medical books. Hence, a calorie in medicine is equivalent to a kilocalorie in physics. When we say one teaspoonful of sugar gives us 20 calories, it implies that if all the energy in the sugar is converted into heat energy, it will raise the temperature of 20 litres of water by 1^oC or 1 litre of water by 20^oC.

All the food one consumes is not converted into heat energy in the body. Were it so, a person would have been burnt to death with the food he consumes. The energy derived from food is utilised for various purposes and assumes various forms of energy such as –

A.   Heat energy which is responsible for the maintenance of body temperature.

B.   Sound energy which produces the sound required to speak, cry, shout etc.

C.   Electrical energy necessary for the production and transmission of nerve impulses, cardiac impulses.

D.   Mechanical energy required for body movements such as walking, running, contraction and relaxation of the heart muscles.

 E.   Chemical energy required for the action of various enzymes in the body, e.g. ptyalin in saliva helps in the conversion of carbohydrates into sugar.

F.   Mental energy, e.g. energy required to store information in the mind, for memory, to think, to remember etc. Thus, energy obtained from food can be used for all the activities of the mind and body.

3.  How many calories are supplied by common food items ?

The calories, i.e. energy in food is supplied only by the  proteins, fats and carbohydrates in the food. One gram of protein and carbohydrate supplies 4.1 calories while 1 gram of fat supplies 9.3 calories.

The calories supplied by 100 grams or 100 ml. of various food items are given in the following table.

Food items (100 gm)	Calories supplied	Food items  (100 gm)	Calories supplied
Fats : Ghee and oil	900	Milk : Buffalo	117
Butter	730	Cow	65
Cashewnut	600	Eggs	170
Dry coconut	730	Fish	100
Wet coconut	440	Meat	194
Sugar based products : Sugar and jaggery	400	Liver	150
Dry dates	280	Fruits	50
Cereals : Rice and wheat	350	Leafy vegetables : Cabbage	30
Pulses : Chana, mung	350	Tubers : Potato, tapioca	100

4.  Which factors affect one’s food requirements ?

The quantity of food required depends on many factors.

A.   As per weight, growing infants in the first year & adolescents require more food per kg. of body weight than an adult.

B.   Pregnant and lactating women require more food.

C.   A man who does hard physical work or exercise would naturally require more food than a person who does sedentary work in the office the whole day.

D.   In cold weather and cold climate greater food intake is required as some of it is utilised to keep the body warm.

E.   During fever and in illness, higher amount of energy is spent to combat the illness.

F.   However, during the acute phase of any illness, the digestive power, appetite and food intake are reduced, as a result of which the patient loses some weight. During convalescence, the digestive power and appetite return to normal and the patient eats more to make up for the loss in weight.

5.  How many calories and proteins do children and adults normally require ?

The approximate daily caloric and protein requirement of children and adults as per Indian standards are as follows.

Age (Years)	Requirement of calories per kg. of body weight	Requirement of proteins in gram per kg. of body weight
Birth to one year	110	2.5 to 3.5
1 to 3 years	100	2.0 to 2.5
3 to 6 years	90	2.0
6 to 9 years	80	2.0
9 to 12 years	70	2.0
12 to 15 years	60	1.7
15 to 19 years	50	1.5
Adults	40	0.8

Normally an adult Indian male requires 2500 to 3000 calories whereas an adult Indian female requires 2200 calories per day. Pregnant and lactating women require an additional 25 gms of proteins and 300 to 500 additional calories per day.

6.  How does one’s activity affect the caloric and protein requirements of one’s body ?

Manual work and physical activity increase the requirement of calories. The daily requirement of calories and proteins for an adult Indian as recommended by the Indian Council of Medical Research is as follows.

7.  What are the manifestations of deficiency in calories ?Energy is stored in the body in the form of fat. Skipping an occasional meal does not give rise to any symptoms as our body has sufficient stores.When a child does not get enough food, i.e. calories over a long period, initially his growth gets stunted. Later, he becomes less active, undernourished and underweight and gets tired easily. His arms and legs appear like sticks and one can easily count his ribs from a distance. His face looks wrinkled like that of an aged person and his joints look prominent. His head appears large because the body is small as his growth is stunted. He becomes cranky and irritable. He is more susceptible to common infections like diarrhoea, cough, cold etc. as he has poor resistance power. Such a child is known as a marasmic child. An adult may also suffer from similar manifestations.

Age (years)	Total calories required per day	Total protein required per day in gram
A man weighing about 55 kg
Light work	2400	55
Moderate work	2800	55
Heavy work	3900	55
A woman weighing about 45 kg
Light work	2000	45
Moderate work	2300	45
Heavy work	3000	45
In pregnancy	2300	100
During lactation	2700	110

7.  What are the manifestations of deficiency in calories ?

Energy is stored in the body in the form of fat. Skipping an occasional meal does not give rise to any symptoms as our body has sufficient stores.When a child does not get enough food, i.e. calories over a long period, initially his growth gets stunted. Later, he becomes less active, undernourished and underweight and gets tired easily. His arms and legs appear like sticks and one can easily count his ribs from a distance. His face looks wrinkled like that of an aged person and his joints look prominent. His head appears large because the body is small as his growth is stunted. He becomes cranky and irritable. He is more susceptible to common infections like diarrhoea, cough, cold etc. as he has poor resistance power. Such a child is known as a marasmic child. An adult may also suffer from similar manifestations.