Risk of haemorrhagic stroke rises with use of vitamin E
Posted 05 November 2010 - 02:32 PM
(Research: Effects of vitamin E on stroke subtypes: meta-analysis of randomised controlled trials)
People should be cautious about indiscriminate widespread use of vitamin E due to an increased risk of a certain type of stroke, warns a new study published on bmj.com today.
An international team of researchers found that taking the vitamin increased the risk of haemorrhagic stroke (where bleeding occurs in the brain) by 22 per cent but reduced the risk of ischaemic stroke by 10per cent.
However, they stress that the absolute effects are small (0.8 more haemorrhagic strokes and 2.1 fewer ischaemic strokes per 1,000 treated persons). In other words, there is the chance of one additional haemorrhagic stroke for every 1,250 people taking vitamin E in contrast to one ischaemic stroke prevented per 476 people taking vitamin E.
They also point out that other preventive strategies, such as blood pressure and cholesterol lowering drugs and living a healthy lifestyle, have far stronger effects on reducing ischaemic stroke than intake of vitamin E.
Previous studies have suggested that taking vitamin E has a protective effect on coronary heart disease and around 13 per cent of the US population takes this vitamin as a supplement. Other studies have found the vitamin has no such effect and in high doses, might increase the risk of death.
Researchers from the US, France and Germany carried out a review of existing studies that had looked at vitamin E and its reported effect on different types of stroke.
They studied nine trials that had investigated the effect of vitamin E on stroke totalling 118,756 participants (59,357 of whom took the vitamin and 59,408 who took a placebo).
Among these, some trials just reported data for total stroke and others had data on both haemorrhagic and ischaemic stroke.
None of the results from the individual trials suggested that vitamin E significantly altered the risk for total stroke. However, the researchers found there were stark differences when looking at the effect of the vitamin by type of stroke.
In the overall analysis, a total of 223 haemorrhagic strokes occurred among 50,334 people assigned to take vitamin E and 183 such strokes among the 50,414 people taking placebo, meaning the group taking the vitamin were 22 per cent more likely to have this kind of stroke.
For ischaemic stroke, the analysis showed that of the 45,670 people taking vitamin E, 884 had this form of stroke, compared with 983 of the 45,733 people taking placebo – meaning people taking the vitamin were 10% less likely to have a stroke.
The researchers conclude: "Given the relatively small risk reduction of ischaemic stroke and the generally more severe outcome of haemorrhagic stroke, indiscriminate widespread use of vitamin E should be cautioned against."
Markus Schurks, Instructor of Medicine, Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
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