Meta-analysis shows vitamin E benefit for PD risk

Vitamin E, but not vitamin C or carotenoids, may have a neuroprotective effect that attenuates Parkinson's disease (PD) risk, say authors of a meta-analysis examining the antioxidants' effects.The authors identified eight studies that provided information on dietary intake of vitamin C, vitamin E and beta carotene and the risk of PD. A meta-analysis of the data showed that moderate intake of vitamin E decreased the risk of developing PD (RR 0.81). There was also a dose-response trend observed with high intake of vitamin E, but this was not significant, which the authors attribute to the small number of studies in the analysis. There were no significant benefits found with moderate or high intake of either vitamin C or beta carotene.Although high dietary vitamin E seemed to confer protection, the authors say the role of supplemental vitamin E is unclear, and referred to one study suggesting synthetic supplements do not provide the same benefit as dietary sources. The lack of benefit could be due to the lower bioavailability and brain penetration with vitamin E supplements, the authors say. It is also possible that high dietary vitamin E may be associated with lower PD risk through lifestyle and behaviour related to vitamin E intake, rather than vitamin E itself.The authors briefly discuss their findings of a lack of protective effect with beta carotene or vitamin C. They suggest that the small number of studies containing information on beta carotene may have affected the results. With respect to vitamin C, they say, "Vitamin C is the most potent antioxidant in plasma; however, its neuroprotective potential may be limited because it is water soluble and required active transport at the choroid plexus to enter the CNS." They also suggest that there is a possible risk of PD with high dietary vitamin C intake, resulting from behaviour related to its intake: "For example, intake of sweet foods, including fruit, which contain vitamin C, might be associated with high PD risk."Reference...