Background

• Vitamin E is a fat-soluble vitamin with antioxidant properties. Vitamin E exists in eight different forms (isomers): alpha, beta, gamma, and delta tocopherol; and alpha, beta, gamma, and delta tocotrienol. Alpha-tocopherol is the most active form in humans. Dosing and daily allowance recommendations for vitamin E are often provided in Alpha-Tocopherol Equivalents (ATE) to account for the different biological activities of the various forms of vitamin E, or in International Units (IU), which food and supplement labels may use. Vitamin E supplements are available in natural or synthetic forms. The natural forms are usually labeled with the letter "d" (for example, d-gamma-tocopherol), whereas synthetic forms are labeled "dl" (for example, dl-alpha-tocopherol).
• Vitamin E has been proposed for the prevention or treatment of numerous health conditions, often based on its antioxidant properties. However, aside from the treatment of vitamin E deficiency (which is rare), there are no clearly proven medicinal uses of vitamin E supplementation beyond the recommended daily allowance. There is ongoing research in numerous diseases, particularly in cancer and heart disease.
• Recent concerns have been raised about the safety of vitamin E supplementation, particularly in high doses. An increased risk of bleeding has been proposed, particularly in patients taking blood-thinning agents such as warfarin, heparin, or aspirin, and in patients with vitamin K deficiency. Recent evidence suggests that regular use of high-dose vitamin E supplements may increase the risk of death (from "all causes") by a small amount, although a different study found no effects on mortality in women who took vitamin E daily. Caution is warranted.

References

• Bairati I, Meyer F, Jobin E, et al. Antioxidant vitamins supplementation and mortality: a randomized trial in head and neck cancer patients. Int J Cancer 2006 Nov 1;119(9):2221-4.
  View Abstract
• Bjelakovic G, Nikolova D, Simonetti RG, et al. Antioxidant supplements for preventing gastrointestinal cancers. Cochrane Database Syst Rev 2008 Jul 16;(3):CD004183.
  View Abstract
• Boshtam M, Rafiei M, Golshadi ID, et al. Long term effects of oral vitamin E supplement in type II diabetic patients. Int J Vitam Nutr Res 2005 Sep;75(5):341-6.
  View Abstract
• Fillenbaum GG, Kuchibhatla MN, Hanlon JT, et al. Dementia and Alzheimer's disease in community-dwelling elders taking vitamin C and/or vitamin E. Ann Pharmacother 2005 Dec;39(12):2009-14.
  View Abstract
• Gao J, Gao X, Li W, et al. Observational studies on the effect of dietary antioxidants on asthma: a meta-analysis. Respirology 2008 Jun;13(4):528-36.
  View Abstract
• Gaziano JM, Glynn RJ, Christen WG, et al. Vitamins E and C in the prevention of prostate and total cancer in men: the Physicians' Health Study II randomized controlled trial. JAMA 2009 Jan 7;301(1):52-62.
  View Abstract
• Isaac MG, Quinn R, Tabet N. Vitamin E for Alzheimer's disease and mild cognitive impairment. Cochrane Database Syst Rev 2008 Jul 16;(3):CD002854.
  View Abstract
• Karlson EW, Shadick NA, Cook NR, et al. Vitamin E in the primary prevention of rheumatoid arthritis: the Women's Health Study. Arthritis Rheum 2008 Nov 15;59(11):1589-95.
  View Abstract
• Lin J, Cook NR, Albert C, et al. Vitamins C and E and beta carotene supplementation and cancer risk: a randomized controlled trial. J Natl Cancer Inst 2009 Jan 7;101(1):14-23.
  View Abstract
• Lee IM, Cook NR, Gaziano JM, et al. Vitamin E in the primary prevention of cardiovascular disease and cancer: the Women's Health Study: a randomized controlled trial. JAMA 2005 Jul 6;294(1):56-65.
  View Abstract
• Mayer-Davis EJ, Nichols M, Liese AD, et al. Dietary intake among youth with diabetes: the SEARCH for Diabetes in Youth Study. J Am Diet Assoc 2006 May;106(5):689-97.
  View Abstract
• Orrell RW, Lane RJ, Ross M. A systematic review of antioxidant treatment for amyotrophic lateral sclerosis/motor neuron disease. Amyotroph Lateral Scler 2008 Aug;9(4):195-211.
  View Abstract
• Sesso HD, Buring JE, Christen WG, et al. Vitamins E and C in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial. JAMA 2008 Nov 12;300(18):2123-33.
  View Abstract
• Walsh PC. Effects of long-term vitamin E supplementation on cardiovascular events and cancer: a randomized controlled trial. J Urol 2005 Nov;174(5):1823-4.
  View Abstract
• Wluka AE, Stuckey S, Brand C, et al. Supplementary vitamin E does not affect the loss of cartilage volume in knee osteoarthritis: a 2 year double blind randomized placebo controlled study. J Rheumatol 2002;29(12):2585-2591.
  View Abstract
• You WC, Brown LM, Zhang L, et al. Randomized double-blind factorial trial of three treatments to reduce the prevalence of precancerous gastric lesions. J Natl Cancer Inst 2006 Jul 19;98(14):974-83.
  View Abstract