THURSDAY, May 19, 2005 (HealthDay News) -- Leafy greens, whole grains, nuts and other foods rich in vitamin E may help prevent Parkinson's disease, according to a new review of eight studies.
The researchers stressed that the finding needs to be verified in clinical trials before vitamin E could be recommended as a means of warding off the condition, however.
Parkinson's is a neurodegenerative disease characterized by a progressive deterioration of motor control. The exact cause of Parkinson's remains unknown.
"We looked at the intake of vitamin E and C and beta-carotene," said lead researcher Mahyar Etminan, a postdoctorate fellow in the Division of Clinical Epidemiology at Royal Victoria Hospital, Montreal, and the Centre for Clinical Epidemiology and Evaluation at Vancouver Hospital, Canada.
"We found that the only intake that proved to be protective [of Parkinson's] was intake of vitamin E," he said.
In their research, Etminan and his colleagues identified eight relevant studies published between 1966 and 2005. Combining data from these studies, they found that individuals with high dietary intake of vitamin E -- those ranked in the top fifth in terms of their daily intake -- decreased their risk of developing Parkinson's by about 22 percent, compared to individuals with low intake of the nutrient.
Intake of vitamin C or beta-carotene appeared to have no protective effect on developing Parkinson's, the researchers add.
The study found a protective effect from vitamin E sourced from food, but whether vitamin E supplements might also be protective remains unclear, Etminan said. The researchers note that at least one study has suggested that supplements do not offer the same benefit as dietary sources of vitamin E.
The study is published online in the June issue of the British journal The Lancet Neurology.
Etminan stressed that these data aren't sufficient to confirm that vitamin E does help prevent Parkinson's. "We probably need to take this hypothesis and test it in a much larger randomized trial," Etminan said. "This is an interesting hypothesis, but it needs to be validated."
He believes that vitamin E might be protective because of its antioxidant effects. "The antioxidant properties may prevent or lower the risk of neuron [brain cell] damage in Parkinson's disease," he noted.
Based on these early findings, the Canadian researcher isn't recommending that people start taking vitamin E.
"However, if they are taking a vitamin E supplement for another reason, or if they have a vitamin E-rich diet, they may get some benefit in terms of protection from Parkinson's," he said. "But this stage, this is more of a hypothesis. At this stage we don't recommend buying vitamin E supplements."
Experts had mixed reactions to the findings.
One sees value in the finding and also believes that vitamin E can slow the progression of Parkinson's.
"This is something that I routinely tell my patients," said Dr. Michele Tagliati, a neurologist at Mount Sinai Medical Center in New York City. "When someone comes in newly diagnosed with Parkinson's, I tell them to put food rich in vitamin E in their diet, because it may have a beneficial effect on the progression of their disease."
Tagliati added, "From my point of view, this finding confirms an impression I had derived from reading the literature."
Another expert took an opposing view. "I think it's silly," said Dr. William Weiner, a professor of neurology and chair of the Department of Neurology and director of the Maryland Parkinson's Disease and Movement Disorders Center at the University of Maryland.
The Canadian study's design -- a meta-analysis, or review of previous literature -- is far from perfect, he said, and the vitamin E finding might simply be a statistical blip. "I think it's not real," he said. "When you do meta-analysis, you put all kinds of things together and get strange answers."
He noted that in one large study, Parkinson's patients were given large doses of vitamin E for a year or longer, and "it didn't make any difference whatsoever in terms of progression of Parkinson's."
Weiner added, "Clinically it doesn't mean anything. The worst thing about this is if people read this and think that they have to take lots of vitamin E. There is no reason to take vitamin E if you have Parkinson's disease or to try and prevent Parkinson's disease."
More information
The National Institute of Neurological Disorders and Stroke can tell you more about Parkinson's disease.
