Last reviewed 30 Sept 2026 · 9 min read
Nutrition
Nutrition is the process by which an organism takes in and uses food for energy, growth, repair and protection. Nutrients are the substances in food that the body needs.
- Macronutrients (needed in large amounts): carbohydrates, proteins, fats, water.
- Micronutrients (small amounts): vitamins and minerals.
- Roughage (dietary fibre) is the indigestible plant material (cellulose) that helps bowel movement and prevents constipation.
Carbohydrates
Provide energy (the main source): about 4 kcal (17 kJ) per gram. Sources: rice, wheat, potato, sugar, fruits. Types: monosaccharides (glucose, fructose, galactose), disaccharides (sucrose, maltose, lactose), polysaccharides (starch, glycogen — the animal store, cellulose). Excess carbohydrate is stored as glycogen and fat. Test for starch: iodine turns blue-black.
Proteins
Body-building food for growth and repair; enzymes, hormones, antibodies and haemoglobin are proteins. About 4 kcal/g. Made of amino acids (20 kinds; 9 essential amino acids must be taken in the diet). Sources: milk, eggs, meat, fish, pulses (dal), soya, nuts. Test: Biuret test (violet colour). Deficiency: kwashiorkor (protein deficiency with adequate energy — swollen belly and swollen limbs) and marasmus (deficiency of both protein and energy — very thin and shrunken body) in children.
Fats (lipids)
Concentrated energy source: about 9 kcal/g; also insulate, protect organs, carry fat-soluble vitamins (A, D, E, K). Sources: oil, ghee, butter, nuts. Excess leads to obesity and heart disease; cholesterol (HDL — "good", LDL — "bad").
Water and fibre
Water: about 60–70 % of body weight; solvent, temperature regulation, transport. An adult needs about 2–3 litres a day. Fibre: whole grains, fruits, vegetables.
Balanced diet
A diet containing all nutrients in the right proportions, with enough calories. The energy needs depend on age, sex and activity. Approximate needs: adult man (moderate work) about 2,300–2,700 kcal/day; woman about 1,900–2,200 kcal/day (the exact figure depends on the ICMR tables); a pregnant or lactating woman needs more.
Vitamins
Organic compounds needed in small amounts; most cannot be made by the body.
- Fat-soluble: A, D, E, K (stored in the body).
- Water-soluble: B-complex and C (not stored; needed regularly).
| Vitamin | Chemical name | Sources | Deficiency disease |
|---|---|---|---|
| A | retinol | carrot, papaya, milk, liver, fish-liver oil, green leaves | night blindness, xerophthalmia |
| B₁ | thiamine | whole grains, pulses, yeast | beri-beri |
| B₂ | riboflavin | milk, eggs, liver | cracks at the mouth corners (cheilosis), sore tongue |
| B₃ | niacin | meat, groundnuts | pellagra |
| B₅ | pantothenic acid | many foods | fatigue |
| B₆ | pyridoxine | meat, whole grains | anaemia, skin problems |
| B₇ | biotin | egg yolk | hair loss, dermatitis |
| B₉ | folic acid | green leafy vegetables | anaemia; birth defects (neural tube) |
| B₁₂ | cobalamin | only animal foods (milk, meat, fish) | pernicious anaemia |
| C | ascorbic acid | amla (richest), lemon, orange, guava, tomato | scurvy (bleeding gums) |
| D | calciferol | sunlight (made in the skin), fish-liver oil, egg yolk | rickets (children), osteomalacia (adults) |
| E | tocopherol | vegetable oils, nuts | (rare) fertility problems, muscle weakness |
| K | phylloquinone | green leafy vegetables, made by gut bacteria | delayed blood clotting |
Hints: Vitamin D is called the "sunshine vitamin"; vitamin K helps blood clotting (Koagulation); vitamin C is destroyed by heat and prolonged cooking; B₁₂ contains cobalt; vitamin B₁₂ is found only in animal foods.
Minerals
| Mineral | Function | Sources | Deficiency |
|---|---|---|---|
| Calcium | bones and teeth, muscle contraction, blood clotting | milk, ragi, green vegetables | rickets, osteoporosis, tooth decay |
| Phosphorus | bones, teeth, ATP | milk, pulses, nuts | weak bones |
| Iron | haemoglobin | green leaves, jaggery, meat, dates | anaemia |
| Iodine | thyroxine | iodised salt, seafood | goitre |
| Sodium and potassium | nerve impulses, fluid balance | salt, fruits, coconut water | muscle cramps |
| Zinc | enzymes, immunity, wound healing | nuts, meat | growth problems |
| Fluorine | tooth enamel | drinking water | tooth decay; excess causes fluorosis |
| Magnesium | enzymes, bones | green vegetables | muscle spasms |
| Copper, cobalt, selenium | trace needs |
Malnutrition and health programmes
- Malnutrition is a lack (undernutrition) or excess (overnutrition) of nutrients. Anaemia, stunting and wasting are widespread in India.
- Government programmes: Mid-Day Meal (now PM POSHAN) for school children, ICDS (Anganwadi) for young children and mothers, POSHAN Abhiyaan (National Nutrition Mission), Anaemia Mukt Bharat, and the National Food Security Act, 2013. The FSSAI regulates food safety. (Check the latest numbers before quoting.)
- Obesity is measured by the Body Mass Index (BMI) = weight (kg) / height² (m²); a BMI of 18.5–24.9 is regarded as normal by the WHO (a lower cut-off for obesity is used for Asians).
A person weighs 72 kg and is 1.80 m tall. — within the normal range.