Supplemental Vitamin E and A, Worth The Risk?

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Perhaps among the most confusing of nutrition and wellness decisions that the average consumer must make is whether to take dietary supplements. The available information is deeply contradictory; while some supplements — like folic acid for pregnant women and vitamin D for babies — are considered nearly essential in medical care, research suggests that other supplements may be ineffective or even deleterious to health. A recent research summary published in The Medical Letter On Drugs and Therapeutics may help consumers and practitioners to wade through the conflicting information on supplements, as many supplements have both risks and benefits associated with their use [1].

Two vitamins with which the article notes significant associated potential risk are vitamins E and A. Vitamin E is a fat-soluble antioxidant that exists in nature in several different forms.

The predominant form of vitamin E found in food sources, including leafy greens, nuts, and some oils, is called gamma-tocopherol. The predominant form in manufactured supplements, however, is alpha-tocopherol. Research suggests that alpha-tocopherol may actually block the activity of gamma-tocopherol, which at least partially explains some of the disturbing research findings associated with vitamin E supplementation. For instance, one study found vitamin E supplements increased the risk of prostate cancer in men by 17% [2], while another study found that vitamin E increased the risk of stroke by 22% and 10%, depending upon the type of stroke [3]. Yet a third study associated vitamin E supplementation with increased overall risk of mortality [4].

Vitamin A occurs in food in two major forms: preformed vitamin A and beta-carotene, which the human body uses to produce vitamin A. Like vitamin E, vitamin A is an antioxidant, though it also plays an important part in vision (particularly night vision) and in normal cell division and development. Food sources of beta-carotene include many fruits and vegetables (especially yellow-orange ones), while animal products such as milk and organ meat contain preformed vitamin A. Despite the importance of vitamin A in the diet, however, in supplement form, it is suspected to act as a pro-oxidant (the opposite of an antioxidant). Supplementation with beta-carotene and/or vitamin A has been found to be associated with or cause a number of negative outcomes. For instance, the study that associated vitamin E with increased overall risk of mortality found the same was true of vitamin A. Two studies found that vitamin A and beta-carotene supplements increased the incidence of lung cancer [5,6], while a third found an increased risk of prostate cancer associated with high blood levels of vitamin A [7].

The risks associated with vitamin E and A supplementation are somewhat disturbing. Without significant evidence to suggest that consuming these vitamins in supplement form confers any particular benefit to outweigh the risks, it’s difficult to rationalize recommending vitamin E and A supplements to the general population (those with absorption disorders and other disease processes that may require vitamin supplementation notwithstanding). In light of these findings, consumers using vitamin supplements that haven’t been prescribed or recommended by a healthcare practitioner may wish to discuss their choices with a doctor. Vitamins from food sources, of course, remain an important and healthy component of diet.

References

1. (No authors listed). Who should take vitamin supplements? Med Lett Drugs Ther. 2011 Dec 26;53(1380):101-3.
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2. Klein et al. Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2011 Oct 12;306(14):1549-56.
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3. Schurks et al. Effects of vitamin E on stroke subtypes: meta-analysis of randomised controlled trials. BMJ. 2010 Nov 4;341:c5702. doi: 10.1136/bmj.c5702.
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4. Bjelakovic et al. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database Syst Rev. 2008 Apr 16;(2):CD007176.
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5. Omenn et al. Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med. 1996 May 2;334(18):1150-5.
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6. Virtamo et al. Incidence of cancer and mortality following alpha-tocopherol and beta-carotene supplementation: a postintervention follow-up. JAMA. 2003 Jul 23;290(4):476-85.
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7. Mondul et al. Serum retinol and risk of prostate cancer. Am J Epidemiol. 2011 Apr 1;173(7):813-21. Epub 2011 Mar 9.
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