A team from Canada and the USA report in the June issue of The Lancet Neurology (issue 4, pp362-5), online today, data from eight studies reveal that moderate or high levels of the vitamin in the diet may help to protect the brain against the disease.
The findings, reported across all national press today, do not however confirm whether there is any benefit from vitamin E supplements. Studies suggest that synthetic supplements do not confer the same benefit as dietary sources.
"No definite conclusions regarding the benefits of supplemental vitamin E can be made," write Mayhar Etminan from the Royal Victoria Hospital in Quebec, Canada and colleagues.
They also call for a large, randomized trial to confirm whether the vitamin does protect against the disease. Some studies have found diets rich in vitamin E to be protective against Parkinson's but others fail to reveal any benefit.
If such a benefit was demonstrated in a large trial, it could have a major impact on the market for vitamin E and vitamin E-rich foods, such as nuts, seeds and green leafy vegetables.
A study showing that the vitamin-like substance CoQ10 could help protect against Parkinson's is thought to be at least partly responsible for the huge demand in this supplement in the last few years.
Parkinson's disease is a progressive neurodegenerative disease thought to affect 1 per cent of people over the age of 65 worldwide. The cause is not understood but it is thought to result from the combined effects of factors including ageing, genetic predisposition, and environmental exposures. Symptoms include tremors, stiffness, slow movement and poor coordination and balance.
The researchers selected relevant studies from 1966 to March 2005 and also looked for benefit from dietary vitamin C and beta-carotene. Neither of these seemed to offer any protection.
Although vitamin C is the most potent antioxidant in blood and, therefore, might be thought to have an effect, it was possible that people who eat a lot of vitamin C-rich foods might be at greater risk of Parkinson's because of their lifestyle, said the researchers.
"For example, intake of sweet foods, including fruit, which contain vitamin C, might be associated with Parkinson's disease risk,"M they write.