The study found that people with the lowest amount of vitamin C in their diets were 30 percent more likely to have a stroke than people with the highest amount of vitamin C in their diets. Smokers with diets high in vitamin C were more than 70 percent less likely to have a stroke than smokers with diets low in vitamin C.
Antioxidants such as vitamin C may protect cells from oxidative stress, which plays a role in stroke.
Vitamin E was also protective for smokers. Those with diets high in vitamin E were more than 20 percent less likely to have a stroke than those with diets low in vitamin E. No similar advantage was found in non-smokers whose diets were high in vitamin E.
"Of course these study findings do not justify smoking. No one should smoke," said study author Monique Breteler, MD, PhD, of Erasmus Medical Center in Rotterdam. "But it is good news that high levels of antioxidants may help reduce the risk of stroke in smokers."
The study involved 5,197 people age 55 or older in Rotterdam, the Netherlands. All of the participants had no cognitive problems, were living independently and had never had a stroke.
The participants were then tracked for an average of 6.4 years. During that time, 253 people had strokes.
People with the highest amount of vitamin C in their diets consumed greater than 133 mg of vitamin C per day. People with the lowest amount in their diets consumed less than 95 mg per day.
To determine their levels of vitamin C and other antioxidants, participants first indicated on a checklist all foods and drinks they had consumed at least twice a month during the past year. Then they were interviewed by a dietician about their diet.
The use of dietary supplements containing vitamins C and E and other antioxidants did not decrease the risk of stroke. Breteler said this finding does not mean that supplements have no potential to have a beneficial effect. Differences in the use of supplements and dietary habits - such as the fact that dietary intake reflects long-term habits and supplement use is generally shorter term and higher dose, as well as the possibility that people who take supplements may be already at greater risk of stroke - may explain why no effect was found, Breteler said.
Rich sources of vitamin C include oranges and other citrus fruits, strawberries, red and green peppers, broccoli and brussels sprouts. Sources of vitamin E include vegetable oils such as sunflower seed, cottonseed, safflower, palm and wheat germ oils, margarine and nuts.
The study was supported by the Netherlands Organization for Scientific Research, the Netherlands Health and Development Research Council and the city of Rotterdam. One of the study co-authors was supported by the Hungary Ministry of Health, the Netherlands Institute for Health Sciences and Erasmus University.
The American Academy of Neurology, an association of more than 18,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as stroke, Alzheimer's disease, epilepsy, Parkinson's disease, autism and multiple sclerosis.
For more information about the American Academy of Neurology, visit its web site at www.aan.com.