Olive oil, sunflower seeds, almonds, greens and other foods rich in vitamin E could help prevent Parkinson's disease, according to published research.

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.

However, by combining all the studies so far on vitamin E, scientists in Canada and the U.S. 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 online 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.

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 randomized clinical trial."

Vitamin E has endured some bad news of late, though. In April, a study published in the New England Journal of Medicine found that super-high doses of vitamin E (2,000 IU daily) had no benefit for people with mild cognitive impairment, a pre-Alzheimer's disease condition. A month earlier, study results in the Journal of the American Medical Association showed that 400 IU of the vitamin daily did not lower heart or cancer risk for people with vascular disease or diabetes. Worse, the vitamin was associated with a 13% increase in the risk for heart failure -- possibly a chance finding but worrisome nonetheless.

These discouraging findings came on the heels of a meta-analysis -- a systematic re-analysis of previously published studies -- published in the Annals of Internal Medicine in November 2004 that found doses of 400 IU or more of vitamin E may increase the chances of earlier death or, to use the researchers' parlance, "all-cause mortality."

This does not mean that vitamin E in food is bad for you, researchers caution. In fact, a number of studies attest to the benefits of dietary vitamin E. Nor are multivitamins anything to worry about. Most brands contain 30-45 IU of the vitamin, which, in its synthetic form, comes to about the Recommended Dietary Allowance of 15mg, which is far less than the high doses linked to health problems.

However, for people taking AREDS vitamins, a combination of high-dose vitamins, zinc and copper that includes 400 IU of vitamin E, the choice is much harder.

AREDS vitamins are recommended for people who have an intermediate case of macular degeneration or who have an advanced case in one eye. Macular degeneration is caused by a breakdown of cells in the macula, the small area in the center of the retina. It is the most common cause of vision loss in people over age 60. It is not readily treatable like cataracts, although doctors are making headway.

Still, the vitamin E saga has unwritten chapters. If additional negative findings come out, we may see an AREDS pill without vitamin E.