A new study suggests that increased levels of vitamin D may improve cardiovascular health and reduce the prevalence of peripheral arterial disease (PAD).

PAD is associated with decreased blood flow in the legs, and occurs when arteries in the legs become narrowed or clogged with fatty deposits. According to 2008 statistic from the American Heart Association (AHA), PAD affects approximately 8 million Americans and is associated with significant disease and death.

Data from 4,839 participants in the National Health and Nutrition Examination Survey (NHANES) showed that the prevalence of PAD was 4.4 percent lower in people with blood levels of vitamin D above 29.2 ng/mL than in people with blood levels below 17.8 ng/mL.

During the study, blood levels of 25- hydroxyvitamin D (25(OH)D)—the non-active storage form of the vitamin—were specifically monitored. The average age of the large, nationally representative study sample was 61.2, and the participants were divided into four groups according to their 25(OH)D levels. Researchers found that increasing levels of the vitamin were associated with lower prevalence of PAD, from 8.1 percent in the group with the lowest 25(OH)D levels to 5.4 percent, 4.9 percent and 3.7 percent prevalence in the groups with increasing vitamin D levels.

When the researchers adjusted for age, sex, race and co-existing health problems, they found that PAD was 64 percent more common in the group with the lowest vitamin D levels compared with the group with the highest levels. For each 10 ng/mL drop in vitamin D level, the risk for PAD increased by 29 percent.

Moreover, the relationship was consistent across the difference subgroups. The authors note that the relationship does not prove that increased levels of vitamin D protect against PAD directly, and that higher vitamin D levels may be a marker of general or specific lifestyle practices. They add that the potential mechanism by which vitamin D may improve cardiovascular health is not known and is controversial.

“In some studies, low 25(OH)D levels have been associated with increased prevalence of coronary heart disease (CHD), stroke and congestive heart failure; however, low 25(OH)D has been associated with a protective association in other studies,” they say.

Melamed adds, "We know that in mice, vitamin D regulates one of the hormone systems that affects blood pressure. Since cells in the blood vessels have receptors for vitamin D, it may directly affect the vessels, although this has not been fully worked out."

The researchers call for large randomized clinical trials to address if vitamin D supplementation could offer protection against PAD.

The results of the study are published in the journal Arteriosclerosis, Thrombosis, and Vascular Biology, and were also presented at the AHA’s Arteriosclerosis, Thrombosis and Vascular Biology Annual Conference 2008.