"There is currently quite a lot of enthusiasm for vitamin D supplementation, of both individuals and populations, in the belief that it will reduce the burden of many diseases," said Dr. Andrew Grey, an associate professor of medicine at the University of Auckland in New Zealand and co-author of an editorial in the July 12 issue of the Archives of Internal Medicine.
"This enthusiasm is predicated upon data from observational studies -- which are subject to confounding, and are hypothesis-generating rather than hypothesis-testing -- rather than randomized controlled trials," Grey said. "Calls for widespread vitamin D supplementation are premature on the basis of current evidence."
In another report involving vitamin D and brain health, researchers led by Paul Knekt and colleagues at the National Institute for Health and Welfare in Helsinki, Finland, found that people with higher serum levels of vitamin D appear to have a lower risk of developing Parkinson's disease.
Their report was published in the July issue of the Archives of Neurology.
For the study, Knekt and his team collected data on almost 3,200 Finnish men and women aged 50 to 79 who did not have Parkinson's disease when the study began.
Over 29 years of follow-up, 50 people developed Parkinson's disease. The researchers calculated that people with the highest levels of vitamin D had a 67 percent lower risk of developing Parkinson's disease compared with those with the lowest levels of vitamin D.
"In conclusion, our results are in line with the hypothesis that low vitamin D status predicts the development of Parkinson's disease," the researchers wrote.
"Because of the small number of cases and the possibility of residual [factors that might influence the results], large cohort studies are needed. In intervention trials focusing on effects of vitamin D supplements, the incidence of Parkinso
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