Researchers at UC Berkeley discovered vitamin E in 1922, and since then countless studies have been done on this still mysterious substance. Because its chief function seems to be as an antioxidant, neutralizing potentially harmful free radicals in the body, vitamin E became a superstar as the antioxidant theory of disease gained wider and wider attention. Would high doses of supplemental vitamin E prove to be the key to good health—preventing cancer, heart disease and Alzheimer’s, as well as producing glowing skin, good eyesight and other benefits? Studies have yielded contradictory findings, but so far the answer seems to be no.
People, including researchers, hold markedly different beliefs about vitamin E supplements, ranging from “protective” to “useless” to “harmful.” Some doctors take vitamin E, but don’t recommend it for their patients. Some do the reverse. Some experts think there have been too many vitamin E studies and say it’s time to quit expecting health benefits. Others say nearly all the research has been flawed and recommend starting afresh using even higher doses of vitamin E or different forms of it.
Early studies (mostly observational and not always well-designed) found a benefit, especially for preventing heart disease, while later studies (many of them well-designed clinical trials) have not. Indeed, a few recent studies suggested that vitamin E supplements might actually be harmful. But the now-discredited claims for vitamin E persist widely on the Internet and elsewhere, and even some scientists continue to believe them.
What the studies show
In 1994, reacting to promising research, the UC Berkeley Wellness Letter began recommending 400 IU of supplemental vitamin E a day. In 2001, after subsequent clinical trials yielded disappointing or conflicting results, we halved our suggested amount to 200 IU. In 200, a meta-analysis from Johns Hopkins Medical Institutions concluded that high dosages of vitamin E (more than 400 IU a day) taken long term may increase the risk of dying by four percent. However, many researchers raised questions about the way the analysis was done. In 2005, after more disappointing studies came out, we stopped recommending E altogether.
Cardiovascular disease. It’s logical that vitamin E might help prevent heart disease because of its antioxidant properties (free radicals are believed to be a factor in atherosclerosis), but supplements have not proved helpful. And many experts now have questions about the theory that antioxidants can prevent heart disease. In 2008, the Physicians’ Health Study II produced negative results: Among more than 14,000 male doctors taking high doses of vitamin C or 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.
In 2010, a meta-analysis published in BMJ concluded that while vitamin E reduces the risk of ischemic stroke by 10 percent, it increases the risk of hemorrhagic stroke by 22 percent. Thus, the researchers warned against widespread use of vitamin E.
A 2012 study by researchers at the University of Utah, published in Hypertension, found that high-dose vitamin C (combined with vitamin E and alpha lipoic acid) improved arterial function in people over 70 but, surprisingly, disrupted it in people in their twenties. Also in 2012, a study in Circulation: Heart Failure found that vitamin E supplements did not reduce the risk of heart failure in female health professionals taking part in the Women’s Health Study.
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 evidence. Other large reviews also have suggested that vitamin E supplements and other antioxidant pills are associated with increased mortality.
Other large reviews have also suggested that vitamin E supplements and other antioxidant pills don’t help and may hurt. One such study, published in the Journal of the American Medical Association in 2007, pointed to a slight increase in mortality for those taking antioxidant supplements, including vitamin E.
Lung cancer. 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.”
Chronic lung disease. In another analysis from the Women’s Health Study, women taking vitamin E every other day for a decade had a 10 percent reduced risk of chronic lung disease. The researchers noted that two previous clinical trials found no such effect.
Prostate cancer. While some early studies suggested a protective effect, more recent research has not. In 2008, the important Selenium and Vitamin E Cancer Prevention Trial (SELECT), which involved 35,000 men, found no benefit over five years. In 2011, after three more years of follow-up, researchers found that the men who had taken vitamin E (400 IU a day of the synthetic form) had a 17 percent increased risk of prostate cancer, compared to those taking a placebo; this was published in the Journal of the American Medical Association. This suggests that effects of supplements can show up years after people stop taking them.
Cognition and Alzheimer's disease. A study published in the Archives of Neurology in 2005 found that people over 65 given high doses of C and E had a reduced risk of developing Alzheimer’s disease. This finding has not been replicated in other research. According to a Cochrane Collaboration review in 2008, there is no convincing evidence that E supplements can prevent or treat cognitive impairment or Alzheimer’s disease.
Macular degeneration. Research about vitamin E has been inconclusive. Another review from the Cochrane Collaboration, looking at the potential role of various antioxidants in preventing macular degeneration, concluded that accumulating evidence indicates that vitamin E does not prevent or delay the onset of the condition. The vitamin may still play a role in treatment, however. Thus, it is an ingredient in the special formulations (PreserVision and similar supplements) that have been shown to slow the progression of the disease.
Cataracts. In 2010, a large, well-designed Harvard study of healthy male doctors suggested that high doses of vitamin E and C, alone or in combination, did not reduce the risk of cataracts over an eight-year period.
Exercise performance. In 2009, a German study on vitamins C and E, published in the Proceedings of the National Academy of Sciences, suggested that instead of protecting athletes, the supplements may block some of the benefits of exercise, notably its ability to improve insulin sensitivity and boost the body’s natural antioxidant system.
Bottom line: There is little clinical research showing that vitamin E supplements are beneficial. Most clinical trials from the past few years have yielded negative or inconclusive results. In fact, the evidence is growing stronger that vitamin E supplements might actually be harmful in some circumstances. Future research may still find that certain “natural” forms of vitamin E are beneficial in some populations (based on age or genetic characteristics, for example), but that remains hypothetical.
Originally published April 2013. Updated January 2014.