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Vitamin E

Vitamin E

Vitamin E is a fat-soluble vitamin found in green leafy vegetables, whole grains, nuts and seeds, wheat germ, eggs, and in oils derived from soybeans, almonds, safflower, and sunflower. It is also an antioxidant and is said to confer protection against Alzheimer’s, Parkinson’s, cardiovascular disease, arthritis, and cancer.

Although observational data suggest a correlation between high intake of foods rich in vitamin E and lowered risk of cancer, randomized trials using vitamin E supplements failed to validate those findings; some studies suggest that vitamin E supplementation can actually increase all-cause mortality.

In addition, because of its antioxidant property, vitamin E can interfere with the actions of certain chemotherapeutic agents.

Further studies are needed to resolve the uncertainty over vitamin E supplementation in disease prevention. Many studies now show that dietary supplements are not equivalent to foods in efforts to obtain sufficient vitamin levels.

—Barrie Cassileth, PhD

ALSO KNOWN AS: Tocopherol, alpha-tocopherol, dl-tocopherol, tocotrienol.

SUMMARY: Vitamin E is a fat-soluble vitamin found in green leafy vegetables, whole grains, nuts and seeds, wheat germ, eggs, and in oils derived from soybeans, almonds, safflower, and sunflower. It acts as an antioxidant and is purported to help prevent Alzheimer’s disease, Parkinson’s disease, cardiovascular disease, arthritis, and cancer. The supplemental form of vitamin E is available in the form of topical oils and as tablets and capsules.

The hypothesis that vitamin E reduces oxidative stress has prompted research into vitamin E for disease prevention over the last two decades.VitE

Vitamin E supplementation was shown to improve immune response in the elderly, and to slow the progression of Alzheimer’s disease,[1] but was ineffective in arresting the development or progression of early Parkinson’s disease[2] and macular degeneration.[3]

Other studies failed to support benefits of vitamin E in reducing the incidence of acute respiratory tract infections[4] and in lowering the risk of cardiovascular disease; vitamin E actually may increase the risk of stroke.[5]

The role of vitamin E in cancer prevention is ambiguous. Data from observational studies suggest a positive association between consumption of foods high in vitamin E and reduced risk of cancer.[6] Vitamin E supplementation was also effective against hot flashes in breast cancer survivors,[7] and in reducing neurotoxicity in patients treated with cisplatin.[8]

However, supplementation with vitamins E, C, and beta carotene did not prevent cancer incidence in randomized clinical trials,[9] nor did it affect cancer mortality.[10]

The large prevention study SELECT (Selenium and Vitamin E Cancer Prevention Trial), based on previous data indicating that selenium and vitamin E reduced the incidence of prostate cancer, also failed to support their protective effects. The trial was suspended in January 2009, when initial data analysis showed no reduction in the risk of prostate cancer with selenium alone or with vitamin E.[11]

Vitamin E supplementation may also increase the risk of lung cancer[12] and overall mortality.[9]

ADVERSE REACTIONS: Daily supplementation over 400 IU may increase all-cause mortality.[13]

Vitamin E supplementation may increase the risk of hemorrhagic stroke.[5]

Warfarin: It has been reported that vitamin E at doses greater than 400 IU per day may increase the effects of warfarin, but data are inconsistent.[14,15]

References

REFERENCES

1. Engelhart MJ, et al: Dietary intake of antioxidants and risk of Alzheimer disease. JAMA 287:3223-3229, 2002.

2. Parkinson Study Group: Effects of tocopherol and deprenyl on the progression of disability in early Parkinson’s disease. N Engl J Med 328:176-183, 1993.

3. Taylor HR, et al: Vitamin E supplementation and macular degeneration: Randomised controlled trial. BMJ 325:11-16, 2002.

4. Graat J, et al: Effect of daily vitamin E and multivitamin-mineral supplementation on acute respiratory tract infections in elderly persons: A randomized controlled trial. JAMA 288:715-721, 2002.

5. Sesso HD, et al:Vitamins E and C in the prevention of cardiovascular disease in men. The Physicians’ Health Study II Randomized Controlled Trial. JAMA 300:2123-2133, 2008.

6. The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group: The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. N Engl J Med 330:1029-1035, 1994.

7. Barton D, et al: Prospective evaluation of vitamin E for hot flashes in breast cancer survivors. J Clin Oncol 16:495-500, 1998.

8. Pace A, et al: Vitamin E neuroprotection for cisplatin neuropathy: A randomized, placebo-controlled trial. Neurology 74:762-766, 2010.

9. Bjelakovic G, et al: Antioxidant supplements for prevention of gastrointestinal cancers: A systematic review and meta-analysis. Lancet 364:1219-1228, 2004.

10. Lin J, et al: Vitamins C and E and beta carotene supplementation and cancer risk: A randomized controlled trial. J Natl Cancer Inst 101:14-23, 2009.

11. Lippman SM, et al: Effect of selenium and vitamin E on risk of prostate cancer and other cancers: The Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA 301:39-51, 2009.

12. Slatore CG, et al: Long-term use of supplemental multivitamins, vitamin C, vitamin E, and folate does not reduce the risk of lung cancer. Am J Respir Crit Care Med 177:524-530, 2008.

13. Miller ER, et al: Meta-analysis: High-dosage vitamin E supplementation may increase all-cause mortality. Ann Intern Med 142:37-46, 2005.

14. Corrigan JJ, Marcus FI: Coagulopathy associated with vitamin E ingestion. JAMA 230:1300-1301, 1974.

15. Kim JM, White RH: Effect of vitamin E on the anticoagulant response to warfarin. Am J Cardiol 77:545-546, 1996.

 
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