Are Vitamin E Supplements Healthy or Harmful?
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Dr. John Swartzberg is an internist and specialist in infectious disease and chairman of the editorial board of the UC Berkeley Wellness Letter and berkeleywellness.com. He is also a clinical professor emeritus of medicine at the University of California, Berkeley School of Public Health and the University of California, San Francisco School of Medicine. He contributed this article to Live Science's Expert Voices: Op-Ed & Insights.

It's been nearly a century since researchers at the University of California, Berkeley discovered vitamin E, and since then, many studies have looked at the potential health benefits of this antioxidant. After all, in lab experiments, antioxidants neutralize potentially harmful free radicals. Shouldn't they confer the same benefits in the body? Over the years, supplement makers and some researchers predicted that vitamin E would help prevent cancer, heart disease and Alzheimer's disease, as well as help maintain eyesight and keep skin glowing. Fueled by hope and hype, vitamin E supplement sales soared.

But what does the research actually show? Early studies that found a benefit, mostly for heart disease, were observational and not always well designed: Researchers asked people if they took vitamin E supplements and then looked at their health. 

More recent studies, however — most of them well-designed clinical trials — have found no benefit. In fact, a few studies suggest that high doses of vitamin E might actually be harmful. [Dangers Lurking in Supplements Prove Need for Oversight (Op-Ed )]

Here are some findings from the more important studies on vitamin E supplements:

  • Heart Disease and Stroke: In 2008, the Physicians' Health Study II looked at more than 14,000 male doctors taking high doses of vitamin C or vitamin E for eight years. Neither supplement reduced heart attacks, strokes or cardiovascular deaths. In fact, vitamin E slightly increased the risk of hemorrhagic (bleeding) strokes. This study was followed by an analysis of many studies in 2010 that found vitamin E supplements increase the risk of hemorrhagic strokes by 22 percent. 
  • Longevity: According to a review of studies that included almost half a million people, antioxidant supplements (including vitamin E, beta carotene, vitamin C and selenium) did not prolong life or protect against disease. This review was done by the Cochrane Collaboration, an independent group that evaluates health research evidence. Other large reviews also have suggested that vitamin E supplements and other antioxidant pills are associated with increased mortality.
  • Vitamin supplements, including vitamin E, have not proved protective, according to a 2007 study funded by the National Cancer Institute (NCI). Smokers who took E supplements actually had a slightly higher risk of lung cancer. Though this is not the final word, the researchers warned smokers that the supplements "may be detrimental."
  • Prostate Cancer: A 2011 study funded by the National Cancer Institute examined whether vitamin E might help prevent prostate cancer. Earlier research had found no benefit or harm from vitamin E. This large study of 35,533 men over a period of three years came up with a surprising result. Healthy men taking vitamin E actually had a higher incidence of prostate cancer than other men. 

In general, there's little clinical research showing that vitamin E supplements benefit your health. Most recent clinical trials have been negative or inconclusive. 

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There are, however, people with a couple of conditions who may want to discuss these supplements with their doctor. Research has found that vitamin E supplements there is some evidence that vitamin E may reduce liver damage caused by inflammation from aggressive nonalcoholic fatty liver disease (NAFLD), a disease associated with obesity. There's no standard medical treatment for this life-threatening disease. Vitamin E therapy showed an improvement in patients with aggressive symptoms who do not have diabetes or cirrhosis. 

People with macular degeneration, the leading cause of blindness in adults, should also talk with their doctor about special formulations of antioxidant supplements — including vitamin E — that slow progression of this incurable eye disease. Two large clinical trials sponsored by the National Eye Institute found that formulations of vitamin C, vitamin E, beta carotene, lutein, and zeaxanthin reduced the risk this serious disease progressing by 25 percent. 

My advice? For most people, healthy food is the best bet. No studies have found harm from consuming the low levels of vitamin E found naturally in foods such as nuts, seeds, vegetable oils, whole grains and leafy greens. 

If you're diagnosed with NAFLD, ask your doctor whether the potential benefit from vitamin E might outweigh risks in your case. If you're at high risk for developing macular degeneration, ask your eye care doctor if you should consider taking the special formulation of antioxidants and zinc. 

Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google+. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Live Science.