Vitamin D deficiency might be linked, among other diseases, to an increased risk of Parkinson’s disease, according to a study published in the October issue of Archives of Neurology.

Parkinson’s disease is thought to be an interaction between genetic and environmental factors. Symptoms of the disease include tremors and muscle rigidity. In the United States, it is estimated that 60,000 new cases are diagnosed each year, joining the 1.5 million Americans who currently have Parkinson’s disease. While the condition usually develops after the age of 65, 15 percent of those diagnosed are under 50.

The study was led by Marian Evatt, MD, assistant professor of neurology at Emory and colleagues. It involved 100 Parkinson’s patients, 97 Alzheimer’s patients and 99 healthy people of the same age.

Overall, more than half of patients with Parkinson’s (55 percent) had low levels of vitamin D, along with 41 percent of those with Alzheimer’s disease. Only 36 percent of health elderly people had low levels of vitamin D.

The average vitamin D concentration among Parkinson's patients was 31.9 nanograms per milliliter, compared with 34.8 nanograms among Alzheimer's patients, and 37 nanograms among healthy people.

Moreover, more Parkinson’s patients were clinically deficient in vitamin D, 23 percent, compared to 16 percent of Alzheimer’s and 10 percent of people with neither disorder.

“We found that vitamin D insufficiency may have a unique association with Parkinso’s, which is intriguing and warrants further investigation,” Dr. Evatt said.

However, the study doesn’t clarify whether the decrease in vitamin D levels in Parkinson’s is a cause or effect of the condition.

“Further research is required to determine at what stage the deficiency in vitamin levels occur in the brains of people with Parkinson's and whether the provision of a dietary supplement, or increased exposure to sunlight may help alleviate symptoms or have an effect on the rate of the condition's progression,” Dr Kieran Breen, director of research, Parkinson’s Disease Society, said.

Vitamin D helps the body metabolize calcium playing a central role in bone formation. Recently, studies have linked vitamin D deficiency to a series of diseases including cancer, high blood pressure, multiple sclerosis, autoimmune diseases, diabetes, and diseases of the nervous system.

Studies have also shown that 50 to 60 percent of people do not have the satisfactory amount of vitamin D. But what is the right amount of vitamin D? Health care providers recommend 200 units daily for people up to age 50, 400 units for adults ages 51 to 70 and 600 units for those 71 and older. People older than 50 need a higher dose, because the body’s ability to convert the vitamin into its active form begins to decline at age 50.

On Monday, the American Academy of Pediatrics recommended that children receive double the amount of vitamin D, meaning 400 units daily, beginning with the first days of life because it might help reduce the risk of serious diseases.

Besides supplements, vitamin D can also be found in fish, fortified cereals and milk and eggs but anyone who enjoys as much as 10 minutes under the sun’s rays will have the right amount of vitamin D in his body, of course taking care not to get burnt.