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d-Alpha Tocopheryl Succinate (Vitamin E)
Vitamin E, unlike other vitamins, is not a cofactor in the function of specific enzyme systems. Rather, it is a potent antioxidant that protects cells and tissues from oxidative damage induced by free radicals. D-alpha tocopherol is one of eight natural forms of vitamin E, and is the form shown to have the greatest nutritional and biological value, in part because the body preferentially retains it.
Gamma tocopherol, the principal form of vitamin E in the U.S. diet, is also an effective antioxidant that complements the activity of alpha tocopherol. The gamma form, however, is removed from circulation and excreted by the body relatively quickly.
The antioxidant activity of vitamin E is wide-ranging. Because it is a fat-soluble vitamin, its protective effects involve the inhibition of lipid (fat) oxidation in the gut, blood stream, tissues, and cells. Specific activities include suppression of free radical formation, suppression of oxidative chain reactions, and repair of damaged cell constituents, particularly cell membranes.
These actions result in protection against several important degenerative disorders, including Alzheimer's disease, certain cancers, and - most notably - heart disease. A study involving 2,000 patients with heart disease found that vitamin E supplements reduced heart attacks by 75%. Two Harvard studies involving a total of ~135,000 health professionals found that those who took daily supplements of vitamin E had one-fourth to one-third less coronary risk than those who did not take the supplements. In a recent study, vitamin E supplementation was further shown to boost immune function, particularly in the elderly.
In conclusion, sound clinical evidence supports the value of vitamin E supplementation.
Food sources of vitamin E include vegetable oils and products made from these oils, wheat germ, nuts, and other grains. The RDA for vitamin E in adults ranges from 15-19 mg/day, while the average dietary intake of vitamin E among adults is less than 10 mg per day. Reported therapeutic benefits of vitamin E intake generally require supplementation of 200-800 mg per day.
Vitamin E is relatively non-toxic when taken orally. However, in people deficient in vitamin K or participating in coumadin therapy, levels higher than 1,000 mg per day may potentially increase bleeding time.
For additional information (including a list of references), please refer to the vitamin E technical bulletin at http://www.usana.com/dotCom/company/science/components.
Dietary Supplement Fact Sheet: Vitamin E (from the National Institute of Health)
Vitamin E - U.S. National Library of Medicine
Vitamin E - Wikipedia
Vitamin E - Mayo Clinic
Vitamin E - Linus Pauling Institute