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March 14, 2011 -- A study of newly diagnosed patients with Parkinson’s disease found a high prevalence of vitamin D insufficiency, but vitamin D levels did not continue to decline as the disease progressed.

The research is one of several studies suggesting a link between low vitamin D levels and Parkinson’s disease, a brain disorder that leads to tremors and problems with balance and coordination. Parkinson’s affects as many as 1 million older Americans.

In a study from Finland published last summer, people with the lowest levels of vitamin D were significantly more likely to develop Parkinson’s over almost three decades of follow-up, compared to people with the highest blood levels of the vitamin.

In the newly published study, almost 70% of patients with a recent diagnosis of Parkinson’s disease had low blood levels of the vitamin.

But it is not yet clear if vitamin D insufficiency raises Parkinson’s risk or if having high levels of the vitamin is protective, says study researcher Marian L. Evatt, MD, of Emory University School of Medicine and the Atlanta Veterans Affairs Medical Center.

“More research is needed to figure this out,” she tells WebMD. “There is certainly an association, but we can’t say if it is causal.”

Does Vitamin D Protect the Brain?

Most people get the majority of their vitamin D from exposure to sunlight. Salmon, tuna, and fortified milk and other dairy products are the main food sources of the vitamin.

There are suggestions from animal and other studies that vitamin D protects the brain and central nervous system.

If this is the case, it would stand to reason that people with low vitamin D levels would have an increased risk for developing Parkinsons’ and other neurodegenerative disorders like Alzheimer’s disease as they age, Evatt says.

In earlier research, Evatt and colleagues found low vitamin D levels in 55% of Parkinson’s patients they studied, compared to 41% of patients with Alzheimer’s disease and 36% of healthy, elderly study participants.

In the newly published study, the researchers examined the prevalence of vitamin D insufficiency in untreated patients with early Parkinson’s disease. They found that 69.4% of patients had vitamin D insufficiency and 26% had vitamin D deficiency.

The patients were followed for an average of 20 months.

“Contrary to our expectations that vitamin D levels might decrease over time because of disease related inactivity and reduced sun exposure, vitamin D levels increased over the study period,” the researchers write.

They conclude that Parkinson’s patients may have low vitamin D levels for many years before disease symptoms become evident.

Searching for Answers

Feigin is an associate investigator with the Feinstein Institute for Medical Research in Manhasset, N.Y.

“The increase in vitamin D levels over the course of the study, during which there was a significant worsening in Parkinson’s disease signs and symptoms, suggests that simply raising vitamin D levels may not result in improved Parkinson’s symptoms,” he says in a news release.