Olive oil, sunflower seeds, almonds, greens and other foods rich in vitamin E could help prevent Parkinson's disease, according to research published today.
Protection against Parkinson's is something of a holy grail according to Robert Meadowcroft, director of policy at the Parkinson's Disease Society, and so far it has been elusive.
But scientists in Canada and the USA say today that by combining all the studies there have been so far on vitamin E, they have concluded that moderate or high levels in the diet - but not as tablets - may help to protect the brain against the disease. Vitamin C and beta carotene, on the other hand, do not help.
Their work is published on line by the Lancet medical journal. Mayhar Etminan, an epidemiologist at the Royal Victoria hospital and Vancouver hospitals in Montreal, and colleagues say the effect is seen in people who have consistently eaten foods rich in vitamin E. There is no evidence that vitamin E supplements help.
They also say that well-designed clinical trials are needed to confirm their findings before doctors issue any dietary advice.
The researchers found eight studies of sufficient quality which contained data on the vitamin intake of populations and which also registered the numbers who had later been diagnosed with Parkinson's disease.
Some of the studies, taken individually, suggest vitamins are protective and some do not. But combined, they show a benefit for foods rich in vitamin E. This prevention was only effective before the onset of Parkinson's however, and did not help once it had been diagnosed.
There was no clear evidence that vitamin E in supplements was useful. "The role of supplemental vitamin E is not clear, but at least one study suggests that synthetic supplements do not confer the same benefit as dietary sources," they write.
They suggest that the form of vitamin E in food is different from the synthetic version in supplements and that the naturally occurring variety may penetrate to the brain more effectively.
They also say it is possible that the protective effect of sunflower seeds and olive oil may be connected with the lifestyles of those who consume them, which may be different from the lifestyles of those who take supplements.
The same could be true of vitamin C. Although it 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. "For example, intake of sweet foods, including fruit, which contain vitamin C, might be associated with Parkinson's disease risk," they say.
Mr Meadowcroft said the Parkinson's Disease Society advised people to eat a healthy, balanced diet, including olive oil, nuts, fresh green vegetables and salads. "We would now look for a further robust randomised clinical trial."
