Vitamins and Nutrition
Organic compounds needed in small amounts, for reasons that vary.
Vitamins are organic compounds an organism needs in small quantities and cannot synthesise in sufficient amounts. The definition is species-specific: most mammals make their own vitamin C, so it is not a vitamin for them. It is one for humans, guinea pigs and some primates, because a shared ancestor lost the enzyme.
Two groups
| Fat-soluble | Water-soluble | |
|---|---|---|
| Which | A, D, E, K | C and the B complex |
| Stored? | Yes, in liver and fat | Barely; excess is excreted |
| Needed | Less frequently | Regularly |
| Overdose risk | Real, especially A and D | Low, but not zero |
Deficiency diseases
Each classical deficiency disease identified a vitamin. Scurvy (C) killed vast numbers of sailors until citrus was recognised as a cure. Rickets (D) deforms growing bone. Beriberi (B1) followed the milling of rice, which removed the husk containing the vitamin. Pellagra (B3) tracked maize-dependent diets prepared without the nixtamalisation that makes its niacin available.
Several of these were caused by processing methods that removed a nutrient people had previously eaten without knowing why — a recurring pattern in nutrition history.
Supplements are not equivalent to food
Isolated nutrients have repeatedly failed to reproduce the benefits associated with the foods containing them, and some large trials found harm from high-dose supplementation. Whole foods deliver nutrients in combination, with fibre and compounds that affect absorption. Supplements correct documented deficiencies well; they substitute for a diet poorly.