Vitamins

Vitamins are organic compounds needed in small amounts in the diet for specific biological functions, growth and health; lacking one causes a specific disease. They come from many chemical classes, so they cannot be defined by structure.

Our bodies cannot make most of them, though plants make nearly all and gut bacteria make some. They are named A, B, C, D and so on, with sub-groups such as B₁, B₂, B₆, B₁₂. Too much is also harmful, so vitamin pills need a doctor's advice.

The old name 'vitamine' (vital + amine) came from the first ones found having amino groups; most do not, so the 'e' was dropped.

Fat-soluble vitamins A, D, E and K dissolve in fats and oils but not in water, and are stored in the liver and adipose tissue.

Water-soluble vitamins, the B group and C, are excreted in urine and cannot be stored (B₁₂ is the exception), so they must be eaten regularly.

Table 10.3, deficiency diseases: A, xerophthalmia (hardening of the cornea) and night blindness; B₁ (thiamine), beri beri; B₂ (riboflavin), cheilosis, digestive disorders and burning skin; B₆ (pyridoxine), convulsions; B₁₂, pernicious anaemia.

Continued: C (ascorbic acid), scurvy with bleeding gums; D, rickets in children and osteomalacia in adults; E, fragile red blood cells and muscular weakness; K, increased blood clotting time.

Sources: A from fish liver oil, carrots, butter, milk; C from citrus fruits, amla and green leafy vegetables; D from sunlight exposure, fish and egg yolk; E from vegetable oils such as wheat germ and sunflower oil; K from green leafy vegetables; B₁₂ from meat, fish, egg and curd.