vitamin E

vitamin E Generic descriptor for a group of fat‐soluble compounds essential for reproduction in animals. Essential for human beings (not for reproduction, so far as is known) but rarely, if ever, deficient in the diet. Two main groups of compounds have vitamin E activity: the tocopherols and the tocotrienols; there are 4 isomers of each: α‐, β‐, γ, and δ‐tocopherols and α‐, β‐, γ, and δ‐tocotrienols, with differing vitamin potencies.

Vitamin E functions primarily as an antioxidant in cell membranes, protecting unsaturated fatty acids from oxidative damage.

The vitamin E content of foods is expressed as mg α‐tocopherol equivalent (based on the different potency of the different vitamers). Vegetables, seeds, and most vegetable oils are good sources. In the UK and the EU an adequate intake is 0.4 mg/g dietary polyunsaturated fatty acid intake; the US/Canadian RDA is 15 mg/day. The obsolete international unit of vitamin E activity was equal to 1 mg of synthetic α‐tocopherol; on this basis natural‐source α‐tocopherol is 1.49 iu/mg.