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.