Taking vitamin E supplements doesn’t reduce the risk of stroke, and may even be harmful, an analysis of previous research found.
The vitamin raised the risk of a severe type of stroke by 22 percent, while it lowered the risk of a milder kind by 10 percent, according to the study, published Friday in the British Medical Journal.
Exercise as well as medicines to lower blood pressure or cholesterol have a far greater effect on stroke prevention, the researchers, led by Markus Schuerks of Harvard Medical School, wrote in the study. About 13 percent of the U.S. population takes the supplement, they said.
Previous studies of the vitamin’s effectiveness have produced conflicting results, with some showing a protective effect and others seeing no effect and an increase in the risk of early death, the study said.
“Given the relatively small risk reduction of ischemic stroke and the generally more severe outcome of hemorrhagic stroke, indiscriminate widespread use of vitamin E should be cautioned against,” the authors said.
The study pooled data from 9 previous trials involving a total of 118,756 patients, about half of whom took the supplement while the other half took a sugar pill. When the data were analyzed, the researchers found an increased risk of hemorrhagic stroke, and a smaller decrease in ischemic stroke.
The absolute risk is small, the study said. For every 1,250 subjects taking the supplement, one hemorrhagic stroke occurred, while one ischemic stroke was prevented for every 476 patients.
Stroke occurs when a blood vessel carrying oxygen to the brain ruptures or is blocked by a blood clot or some other particle, cutting off the brain’s supply of oxygen. Nerve cells then die, affecting the part of the body they control. These cells aren’t replaced, leading to disability, according to the American Heart Association.
About 800,000 Americans suffer a stroke each year, and 137,000 of them die, according to the association.
Hemorrhagic stroke is caused when tissue is compressed by a hematoma, a collection of blood that has leaked out of a vessel. Ischemic stroke is seen when a loss of blood supply to part of the brain triggers a biochemical reaction that leads to cell death.