Vitamin E may increase risk of certain type of stroke

November 5, 2010

High doses of vitamin E may raise the risk of a serious type of stroke, a new UK study suggests.

The meta-analysis examined data from nine randomized controlled trials investigating the effect of vitamin E on strokes (1). The analysis included 118,765 participants receiving either high doses of vitamin E (between 50 mg and over 200 mg per day) or placebo for a minimum of one year. The study results suggest that vitamin E supplementation increased the risk of suffering a hemorrhagic stroke by 22%, but reduced the risk of ischemic strokes by 10%. In terms of the overall survey, the conclusion was that vitamin E did not significantly alter the risk of having a stroke.

The researchers pointed out that the increased risk of suffering a hemorrhagic stroke was relatively small: among those taking vitamin E, only one additional hemorrhagic stroke occurred per 1,250 individuals. On the other hand, the potentially beneficial effects of vitamin E were also rather small: only one ischemic stroke was prevented per 476 individuals. These findings warrant further research.

Experts commented that maintaining a healthy lifestyle – with a balanced diet, regular exercise and monitoring of blood pressure – is key in reducing the risk of having a stroke. An unhealthy lifestyle cannot be compensated for by high doses of vitamin E supplements – in this case four totwenty timesthe RDA used in the EU. However, as large parts of the population do not consume the recommended amounts of vitamin E from foods, dietary supplements can help to meet the recommended daily intakes.

Vitamin E is known to be a powerful antioxidant, and it has been suggested that it helps to prevent cardiovascular disease by stopping fatty deposits building on artery walls. Several observational studies have indicated a protective effect of vitamin E intake on cardiovascular diseases. Most randomized controlled trials reported no clear beneficial effect of vitamin E on the cardiovascular disease risk, which is influenced by multiple factors. Meta-analyses were controversial and have been the subject of much debate as the differences between the pooled individual studies often hamper firm conclusions.

A ‘hemorrhagic’ stroke is caused by a weakened blood vessel (e.g. aneurysm) in the brain that ruptures and bleeds into the surrounding brain. The blood accumulates and compresses the surrounding brain tissue, which can have devastating effects and is sometimes fatal. A hemorrhagic stroke accounts for about 13% of stroke cases. An ‘ischemic’ stroke occurs as a result of an obstruction within a blood vessel supplying blood to the brain. The underlying condition for this type of obstruction is the development of fatty deposits lining the vessel walls, called atherosclerosis. It accounts for 87% of all stroke cases.

References

  1. Schürks M. et al. Effects of vitamin E on stroke subtypes: meta-analysis of randomised controlled trials. British Medical Journal. 2010.