Balanced diet, deficiency diseases and food adulteration
A balanced diet gives every nutrient in the right amount. Too little causes deficiency diseases such as kwashiorkor, goitre and scurvy. Adulterated food harms health.
Nutrients, their jobs and sources
| Nutrient | Main job | Good sources |
|---|---|---|
| Carbohydrates (sugar, starch, cellulose) | Main source of energy | Rice, wheat, potato, sweet potato, sugarcane, fruits, milk |
| Fats | Rich source of energy; keep the body warm; carry fat-soluble vitamins | Edible oil, ghee, butter, meat, groundnuts |
| Proteins | Growth and repair of body tissues | Milk, dal, eggs, meat, soyabean |
| Vitamins | Normal growth and health; needed in small amounts | Fruits, vegetables, milk, eggs (see the next table) |
| Minerals | Bones and teeth, blood, and the body's daily work | Milk, green leafy vegetables, iodised salt, sea food |
| Water | 65 to 70% of body weight; controls body temperature; the medium for body reactions | Drinking water, fruits, milk |
| Roughage (fibre) | Helps bowel movement and prevents constipation | Salads, raw vegetables, fruits |
What is a balanced diet?
A balanced diet means eating a variety of foods every day, in proper amounts. It gives the body carbohydrates, fats, proteins, vitamins, minerals and water in the correct proportion. The amount a person needs depends on age, sex, the work they do and pregnancy. A farm labourer needs more energy foods than a person who sits at a desk. Eating too little, or the wrong food, for a long time is malnutrition. It causes deficiency diseases. Too much of some vitamins, such as A and D, is also harmful.
Vitamins and minerals: sources and deficiency diseases
| Nutrient | Good sources | Lack of it causes |
|---|---|---|
| Vitamin A | Milk, carrots, tomatoes, eggs | Night blindness (poor sight in dim light) |
| Vitamin B1 | Milk, peas, cereals, green vegetables, meat | Beri-beri (harms the nervous system) |
| Vitamin B12 | Liver, eggs, milk, fish | Anaemia (too few red blood cells) |
| Vitamin C | Amla, tomatoes, citrus fruits, singhara (water chestnut) | Scurvy (swollen, bleeding gums) |
| Vitamin D | Sunlight on the skin, milk | Rickets (soft, bent bones in children) |
| Vitamin E | Vegetable oils, milk, butter, whole grains | Affects fertility (the ability to have children) |
| Vitamin K | Spinach, cabbage, green vegetables | Wounds keep bleeding because blood does not clot |
| Iodine | Sea food, iodised salt | Goitre (swelling of the thyroid gland in the neck) |
| Iron | Green leafy vegetables, sprouts, liver, eggs, meat | Anaemia (less haemoglobin; weakness and a pale look) |
Protein energy malnutrition (PEM): marasmus vs kwashiorkor
PEM is one of three kinds of deficiency disease. The other two are mineral deficiency (goitre, anaemia) and vitamin deficiency (see the table above).
Food adulteration: common adulterants
| Food | Common adulterants |
|---|---|
| Cereals | Straw, husk, stones, poor or insect-damaged grains |
| Pulses (dal) | Straw, kesari dal, poor grains, metanil yellow dye |
| Milk | Water, starch, milk of other animals, synthetic milk; fat removed |
| Edible oil | Argemone oil, mineral oil, artificial colours |
| Turmeric (haldi) | Starch coloured with metanil yellow or chromate |
| Coriander powder | Sawdust, starch, powdered dung |
| Black pepper | Dried papaya seeds |
Activity: test food for starch, fat and adulterants (practical)
**Food adulteration** is mixing food with cheaper, poor-quality, edible or inedible things. Sealed packs from a reliable maker, with a quality mark, are safer to buy.
- 1Starch: boil a few pieces of potato in water, cool and filter. Add 2 to 4 drops of iodine solution. A blue-black colour shows starch.
- 2Fat: crush a groundnut, or a little butter, in a fold of paper and press with your thumb. A greasy, see-through spot shows fat.
- 3Metanil yellow in dal or turmeric: soak the sample in lukewarm water, then add a few drops of concentrated hydrochloric acid. A magenta (pink-purple) colour shows the dye.Use the acid only with a teacher: it burns skin
- 4Starch in milk: boil a little milk, cool it and add iodine. Blue-black means starch, such as arrowroot, was added.
- 5Test a pure sample in the same way to compare. This is a control.
- 6★Record each food, the test, what you saw and your result in a table.
★ key step
Roti or rice with dal, a sabzi, curd and a fruit makes a simple balanced Indian meal. Iodised salt in the kitchen protects the whole family from goitre.
1 marks: “Name the disease caused by a lack of vitamin C.” Scurvy: the gums swell and bleed.
2 marks: “Expand PEM. Name its two diseases and the age group each one affects.” Protein energy malnutrition: a disease caused by too little protein (and energy) in the diet. Marasmus affects babies up to one year; kwashiorkor affects children of 1 to 5 years.
3 marks: “What is a balanced diet? Why does a farm labourer need a different diet from a schoolchild?” A daily diet that gives all nutrients, carbohydrates, fats, proteins, vitamins, minerals and water, in the correct proportion. Needs depend on age, sex, work and pregnancy. A labourer does hard physical work, so needs more energy foods (carbohydrates and fats); a growing child needs plenty of protein.
Vitamin A for eyes (night blindness), B1 for nerves (beri-beri), C for gums (scurvy), D for bones (rickets).