Energy Sources

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

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Last modified: Saturday, 17 March 2012, 5:32 AM