There has been a spate of studies in recent weeks hinting that vitamin supplements might prevent a variety of diseases: Vitamin D seems to cut the risk of rheumatoid arthritis and multiple sclerosis; vitamins C and E have been linked–in a very preliminary way–to lower rates of Alzheimer's. It's tempting to start thinking of vitamins as fix-all wonder drugs. But the human body, unfortunately, is not that straightforward. This week once again demonstrates that there are no simple answers. A major study published today in the Journal of the American Medical Association shows that vitamins don't prevent strokes, which are the third leading cause of death in the United States.
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This study, unlike the Alzheimer's work and some of the vitamin D research, was specifically designed to test the vitamin's protective ability by giving some people high doses and some people low doses and then following everyone for a few years to see what happened to stroke rates. It's the best way to learn if a therapy really works. (The Alzheimer's study, in contrast, tried to re-create people's vitamin-taking history by asking questions about their past habits, and people don't remember exactly what they took or what else they might have done to enhance their health.)
The Vitamin Intervention for Stroke Prevention study involved 3,680 adults who had already had a stroke and thus were at high risk for another one. The vitamins being tested were B6, B12, and folic acid (B9). People in the high-dose group got daily doses of 25 milligrams of B6, 0.4 milligrams of B12, and 2.5 milligrams of folic acid–all much higher than the recommended daily allowances. The low-dose group got doses well below the RDAs.
The bottom line: After two years, the vitamin doses had made no difference in stroke rates.
The B vitamin group is supposed to reduce blood levels of homocysteine, an amino acid that may help build up plaque in blood vessels and thus lead to strokes. And the high-dose vitamin group did do a better job of lowering their homocysteine levels. However, that made no difference where it really counts: strokes, diagnosis of coronary heart disease, or death. That's not to say homocysteine levels themselves have nothing to do with vascular diseases. Several studies show they are a real risk factor. It's just that using extra B vitamins to lower those levels doesn't seem to give people the protection they so badly want.
