WEDNESDAY, April 16 (HealthDay News) -- New research has discovered that people with low blood levels of vitamin D were found to have a higher incidence of peripheral arterial disease (PAD), potentially dangerous blockages in the leg arteries.

The study of nearly 4,900 American adults found more than double the incidence of PAD among those with the lowest levels of vitamin D compared to those with the highest levels.

The finding was presented Wednesday at the American Heart Association's Arteriosclerosis, Thrombosis and Vascular Biology annual conference, in Atlanta.

One previous study found an association between low vitamin D levels and heart disease, said study author Dr. Michal Melamed, an assistant professor of medicine, epidemiology and population health at Albert Einstein College of Medicine in New York City.

"But in that study they found only eight cases of PAD," she said. "In our analysis, we have more than 400 people with PAD."

Vitamin D is made when the body is exposed to sunlight. It is converted to a hormone that makes bones stronger. A severe deficiency can cause rickets in children. The link to blood vessel problems has emerged in recent years.

"The underlying mechanism isn't quite known," Melamed said. "But the study definitely speaks to the fact that it is an association that needs to be further explored."

Current guidelines recommend a vitamin D intake of 400 International Units a day for people aged 50 and older. In addition to sunlight, other sources of the vitamin are salmon, sardines, cod liver oil, fortified milk and some fortified cereals.

Exposure to sunlight "always calls for a balance," Melamed said, because overexposure raises the risk of skin cancer. "I would recommend about 10 to 15 minutes of direct exposure, then putting on sun block," she said.

Supplements aren't recommended by Dr. Thomas J. Wang, an assistant professor of medicine at Harvard Medical School and Massachusetts General Hospital, who led the earlier study.

"There have been a number of very intriguing population findings, but we still don't know if supplementation will affect the risk of cardiovascular disease," Wang said. "A clinical trial would be needed to see if supplementation could avert risk. We know that the things to prevent vitamin D deficiency include sunlight and proper diet."

But Dr. Denise Teves, an endocrinologist who is an assistant professor of medicine at the Medical College of Wisconsin, said a case could be made for vitamin D supplements for some people.

"I recommend supplements for some patients who come to me with metabolic bone disease," she said. "Most have insufficient vitamin D."

Existing guidelines might fall short of what is needed for some people, Teves said.

"The current guidelines do call for 400 units a day," she said. "But in the last two or three years, many endocrinologists have been recommending at least 800 units a day. I have seen many students in Wisconsin in the wintertime with low vitamin D levels."

It's best to consult a doctor about taking large amounts of a vitamin D supplement, Teves said.

More information

A fact sheet on vitamin D is available from the U.S. Office of Dietary Supplements.

SOURCES: Michal Melamed, M.D., assistant professor, medicine and epidemiology and population health, Albert Einstein College of Medicine, New York City; Thomas J. Wang, M.D., assistant professor, medicine, Harvard Medical School and Massachusetts General Hospital, Boston; Denise Teves, assistant professor, medicine, Medical College of Wisconsin, Milwaukee; April 16, 2008, presentation, American Heart Association Arteriosclerosis, Thrombosis and Vascular Biology annual meeting, Atlanta

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