People recently diagnosed with Parkinson's disease are more likely than healthy people to have vitamin D insufficiency, but their vitamin D levels don't appear to decline during the progression of the disease as was previously thought, according to a new study.

At the beginning of the study, 69.4 percent of people with recently diagnosed Parkinson's disease had vitamin D insufficiency and 26.1 percent of people had vitamin D deficiency. (Vitamin D insufficiency was defined as having less than 30 nanograms of vitamin D per milliliter of blood, and vitamin D deficiency was defined as having less than 20 nanograms of vitamin D per milliliter of blood.)

About a year later, 51.6 percent of the Parkinson's patients had vitamin D insufficiency and 7 percent had vitamin D deficiency.

“Contrary to our expectation 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,” study researcher Dr. Marian Evatt, of Emory University School of Medicine in Atlanta, and colleagues wrote in the study.

Therefore, it's possible that long-term vitamin D insufficiency is present before the onset of Parkinson's disease , and could even play a role in the development of the disease, they said. Past research suggests vitamin D may affect Parkinson's risk because there are many vitamin D receptors in the part of the brain affected by the disease.

At this point, the researchers don't have a strong understanding of why Vitamin D levels would actually increase over time.

Researchers measured the vitamin D levels of 157 people who had been diagnosed with Parkinson's disease five or fewer years prior. They collected information on their vitamin D levels at the beginning of the study, and at the study's end a year later.

The study was published in the March issue of the journal Archives of Neurology.

The new study adds to previous research from Evatt. In 2008, she published a study in the journal Archives of Neurology that showed that more people with Parkinson's disease have vitamin D insufficiency (55 percent) than people with Alzheimer's disease (41 percent) and healthy people (36 percent).

Pass it on: Vitamin D insufficiency or deficiency is common in people with Parkinson's disease, but vitamin D levels tend not to decrease once the onset of the disease has already begun.

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