Human Nutrition 3(3+0)

Lesson 6 : Energy – Determination of energy requirements and energy sources

Energy Sources

The main sources of dietary energy are the carbohydrates, fats and proteins. These sources of energy, on complete metabolism, yield different amounts of energy (table). An adequate and constant amount of energy must be made available to the body for cell survival and maintaining the following vital functions at optimal levels.

1. Activity of the brain and the nervous system and transmission of nerve impulses.
2. Pumping of heart and distribution of blood to supply oxygen and nutrients to various tissues, part of it against gravity.
3. Liver function for the catabolism and synthesis of nutrients and other essential bio-compounds and detoxification of toxic chemicals ingested through food and air.
4. Excretory function of the kidney.

Table: Energy yields from various sources of Energy.

Energy source	Gross energy (Kcal/g)	Metabolizable energy (Kcal/g)
Carbohydrate	4.18	4.0
Fat	9.46	9.0
Protein	5.67	4.0
Alcohol	7.10	7.0

The energy value of different groups of food stuffs is given in below Table.

Table: Energy value of foods

Foods	Energy value (Kcal/100g)	Foods	Energy value (Kcal/100g)
Rich Sources Oil and Fats (vegetable oils, ghee and vanaspati)	900	Fair Sources Roots and tubers (potato, tapioca and sweet potato)	120-160
Butter	720	Fresh fruits	30-80
Nuts and oilseeds	500-650	Dilute squash and soft drinks	40-60
Good Sources Cereals and millets	340-360	Tender pulses (green peas etc.)	80-100
Pure carbohydrate foods (sago, sugar, jaggery etc.)	280-400	Meat, fish and eggs	120-180
Dried fruits	300-320	Fresh milk, cow’s	68
Milk powder, full fat	502	Fresh milk, buffalo	117
Milk powder, skimmed	363	Poor Sources Other vegetables	30-40
		Green leafy vegetables	30-40