PD is a progressive neurodegenerative disease with unknown cause. PD is likely to result from the combined effects of multiple factors including ageing, genetic predisposition, and environmental exposures. Some studies suggest that diets rich in vitamin E are protective against PD; other studies show no such benefit.
Mayhar Etminan (Royal Victoria Hospital, Quebec, Canada, and Centre for Clinical Epidemiology and Evaluation, Vancouver, Canada) and colleagues did a meta-analysis to try to establish whether vitamin C, vitamin E, and b carotene can lower the risk of PD. The investigators searched for relevant studies from 1966 to March 2005. They combined the data from eight studies and found that moderate dietary intake of vitamin E decreased the risk of developing PD. However, dietary vitamin C and b carotene did not seem to confer any protective effects. The role of vitamin E supplements is not clear, but at least one study suggests that synthetic supplements do not confer the same benefit as dietary sources, state the authors.
Dr Etminan concludes: "Our data suggest that diets rich in vitamin E protect against the development of PD. No definite conclusions regarding the benefits of supplemental vitamin E can be made. Neither vitamin C nor b carotene seems to have a neuroprotective effect. Given that these data are observational, confirmation from well-designed randomised controlled trials is necessary before suggesting changes in routine clinical practice."