Vitamin E activity is possessed by a number of compounds known as tocopherols. Among these compounds α-tocopherol is known as vitamin E. Structurally vitamin E contains a dihydro benzopyran nucleus with an isoprenoid side chain (Fig. 8.3). Many of them are pale yellow oils soluble in fat.
The principal role of vitamin E appears to be as an antioxidant. By accepting oxygen, vitamin E can prevent the oxidation of vitamin A in the intestinal tract, thus making vitamin A available for body use. Vitamin E also reduces the oxidation of the poly unsaturated fatty acids, thereby helping to maintain normal cell membrane. It protects the red blood cells against hemolysis. Vitamin E is required by animals, and presumably, by humans for the normal reproductive processes. It also plays an important protective role during ageing of cells.
Wheat germ oil and corn germ oil are the rich natural sources. Vegetable oils and fats are good sources. Cereals and animal foods are fair sources of tocopherol.
It is difficult to establish vitamin E requirements. The requirement depends mainly on the intake of poly unsaturated fatty acids. It is generally accepted that the intake of vitamin E should be 0.4 mg α -tocopherol equivalents / g dietary poly unsaturated fatty acid. This does not present any problem, since all foods which are rich sources of poly unsaturated fatty acids are also rich sources of vitamin E.
There is some evidence that higher intake of vitamin E may have a useful protective effect against the development of ischaemic heart disease. This is because high concentrations of vitamin E inhibit the oxidation of poly unsaturated fatty acids in plasma lipoproteins and this oxidation which is responsible for the initiation of atherosclerosis (deposition of fat in the coronory artery walls). The levels that appear to be beneficial are of the order of 17-40 mg α -tocopherol/day, which is above what could be achieved by eating ordinary foods.
Adults : 25 - 30 mg / day
Vitamin E, like other fat soluble vitamins, is absorbed along with fat in the intestines.
It is stored in the liver, muscle and body fat.
Vitamin E deficiency cause the following disorders in animals.
Hemolysis of red blood cells