Vitamin E Supplements and Stroke Risk

BOSTONVitamin E supplements appear to affect the incidence of stroke subtypes, although the actual change is quite small, according to a new meta-analysis (BMJ. 4 Nov 2010; 341:c5702 DOI: 10.1136/bmj.c5702). Previous studies have suggested the lipid-soluble antioxidant vitamin E may fight cardiovascular disease by inhibiting lipid peroxidation. However, studies are inconclusive, with many finding no effect on CVD with vitamin E supplementation.

In the new meta-analysis, coordinated out of Harvard Medical School and the Harvard School of Public Health, researchers evaluated the effect of vitamin E supplementation on incident total, ischaemic and haemorrhagic stroke as reported in nine randomized, placebo-controlled trials published through January 2010. The total number of participants in the studies was 118,765, with 59,357 receiving vitamin E and 59,408 on placebo.

Vitamin E had no effect on the risk for total stroke; however, when examining the stroke subtypes, there was a 22 percent increase in risk for haemorrhagic stroke, and a 10 percent decrease in ischaemic stroke. When comparing the incidences, this translates to 0.8 more haemorrhagic strokes and 2.1 fewer ischaemic strokes for every 1,000 subjects taking vitamin E. Ultimately, though, the researchers cautioned against "indiscriminate widespread use" of vitamin E.

The majority of the studies involved subjects with some type of cardiovascular disease risk or diagnosis. Some, such as the Cambridge Heart Antioxidant Study (CHAOS) involved subjects with proven atherosclerosis; others, such as the GISSI trial, involved patients with recent myocardial infarction. However, the research team said there is no reason to suspect the effects of vitamin E would differ among healthy adults, those with CVD risk factors or those who have experienced cardiovascular events.

Andrew Shao, Ph.D., senior vice president, scientific and regulatory affairs, Council for Responsible Nutrition (CRN), commented that the study, while including a large sample size from high-quality studies, was limited in several ways, including the focus solely on stroke outcomes versus all CVD outcomes. Further, he noted, the meta-analysis only looked at trials in which subjects received only vitamin E. "We know that antioxidantsand indeed all nutrientsdont function in isolation but as part of complex networks, so the idea that a single nutrient, supplemented at high doses in primarily cardiovascular patients or smokers, will have potent effects may be misplaced to begin with," he said. "Even though many studies, including those examined in this analysis, show benefits of supplemental vitamin E, it may be wiser to examine vitamin Es effects in the context of the full antioxidant network, rather than in isolation."