Vitamin E fails to deliver benefits for major cardiovascular events or cancer

Jul 6 2005

In an article in the July 6 JAMA, I-Min Lee, M.B.B.S., Sc.D., of Brigham and Women's Hospital and Harvard Medical School, Boston, and colleagues analyzed data from the vitamin E component of the Women's Health Study, which tested whether vitamin E supplementation decreases the risk of cardiovascular disease and cancer among healthy women.

According to background information in the article, previous observational studies have indicated that vitamin E may be beneficial in lowering the risk for some cardiovascular diseases; and high antioxidant intake has been linked to reduced cancer rates. For small to moderate effects, however, the amount of uncontrolled and uncontrollable confounding inherent in observational studies can be as large as the postulated benefit, so randomized clinical trials represent the most reliable study design strategy. Randomized trials do not generally support benefits of vitamin E, but there are few trials of long duration among initially healthy persons. By 1997, despite a lack of randomized trials, 44 percent of U.S. cardiologists reported routine use of antioxidant supplements, primarily vitamin E, compared with 42 percent who routinely used aspirin for the primary prevention of CVD.

In this component of the Women's Health Study, 39,876 apparently healthy U.S. women aged at least 45 years were randomly assigned to receive 600 IU of natural-source vitamin E on alternate days or placebo, and were followed up for an average of 10.1 years.

The researchers found with the vitamin E group, there was no significant effect on major cardiovascular events, on the incidences of heart attack or stroke, as well as ischemic or hemorrhagic stroke. For cardiovascular death, there was a 24 percent reduction. There was no significant effect on the incidences of total cancer or breast, lung, or colon cancers. Cancer deaths also did not differ significantly between groups. There was no significant effect of vitamin E on total death.

"In conclusion, the WHS does not support recommending vitamin E supplementation for CVD or cancer prevention among healthy women. This large trial supports current guidelines stating that use of antioxidant vitamins is not justified for CVD risk reduction. … The WHS findings should be viewed in the context of the available randomized evidence, as well as data that should be available over the next several years from ongoing trials, including the Physicians' Health Study, which will provide data on primary prevention in men. At present, in the primary prevention of CVD and cancer, therapeutic lifestyle changes including a healthy diet and control of major risk factors remain important clinical and public health strategies," the authors conclude.