Oct. 13, 2008 -- Parkinson's disease patients may be particularly likely to have low blood levels of vitamin D.

Researchers report that news in the Archives of Neurology.

They studied 100 Parkinson's disease patients, 100 Alzheimer's disease patients, and 100 healthy adults of the same age as the Parkinson's and Alzheimer's patients.

Participants provided blood samples, which showed vitamin D insufficiency in 55% of the Parkinson's disease patients, compared to 41% of the Alzheimer's patients and 36% of the healthy participants.

Vitamin D deficiency, in which people have even less vitamin D than people who have vitamin D insufficiency, was also more common among the Parkinson's patients (23%), compared to the Alzheimer's patients (16%) and the healthy participants (10%).

The findings held regardless of people's age, gender, and presence or absence of an Alzheimer's-related mutation in the APOE gene.

The study was a snapshot in time -- it doesn't prove that low levels of vitamin D cause Parkinson's disease or that taking vitamin D would help prevent Parkinson's.