Vitamins

Vitamins are organic micronutrients that the body needs in small amounts but cannot make, or cannot make enough of, on its own — so they must come from the diet. Plants are the original source of most of them: the water-soluble B-complex and vitamin C, vitamin K1, folate, and the carotenoid precursors the body converts into vitamin A. They are grouped not by any shared chemical structure but by this shared quality of being essential, diet-derived, and active in tiny quantities.

They divide broadly into the water-soluble vitamins (the B group and C), which are not stored to any great extent and are topped up from food day to day, and the fat-soluble vitamins (A, D, E and K), which dissolve in the plant's oils and can be held in the body's fat. Green leaves, fruits, seeds and sprouted grains are among the richest plant sources, and a herb's vitamin content is often part of its nutritional, tonic reputation.

As medicinal substances the pattern is straightforward and gentle: at the levels found in food and herbs, vitamins are nourishing and safe, and deficiency rather than excess is the usual concern. Toxicity is almost entirely a matter of concentrated supplementation, and even then it is chiefly the fat-soluble vitamins (notably A and D) that can accumulate to harmful levels, since surplus water-soluble vitamins are largely passed in the urine. From plants, in short, vitamins are food; only isolated high-dose forms warrant real caution.