August 02, 2011

Atherosclerosis Linked to Low Vitamin D - Study

Shonni J. Silverberg, M.D.
Shonni J. Silverberg, M.D.
Investigators have identified new evidence from the Northern Manhattan Study connecting atherosclerosis to low vitamin D levels. They found that low 25-hydroxyvitamin D levels were associated with increased intima-media and maximal carotid thickness in those with plaque.

"Our report demonstrates an independent effect of low vitamin D on subclinical indices of carotid atherosclerosis," senior investigator Shonni Silverberg, MD, from the Columbia University College of Physicians and Surgeons in New York, is quoted as saying. "It is, however, important to note that our observations do not provide insight into the nature of the interaction of low vitamin D with the atherosclerotic process."

The work will be published in the August issue of Stroke but was released early online.

The investigators studied 203 adults from the Northern Manhattan Study who had serum measurements and carotid ultrasonography. They looked at 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, calcium, phosphorus, and parathyroid hormone.

Vitamin D and Carotid Thickness

They found that 25-hydroxyvitamin D was inversely associated with both intima-media thickness (beta, -0.01 per 10-ng/mL increase; P = .05) and maximal carotid plaque thickness (beta, -0.10 per 10-ng/mL increase; P = .03).

In a model containing traditional cardiac risk factors and indices of mineral metabolism, 25-hydroxyvitamin D accounted for 13% of the variance in both intima-media thickness and maximal carotid plaque thickness. Calcium, parathyroid hormone, and 1,25-dihydroxyvitamin D levels were not associated with carotid measures.

"We confirmed prior data showing a relationship of carotid measures with calcium-phosphorus product," Dr. Silverberg said. "More importantly, we found a robust association of vitamin D levels with subclinical markers of carotid atherosclerosis."

Dr. Silverberg pointed out that some of the prior literature in this area did not adequately control for cardiovascular risk factors and renal function, and most of the available data did not account for the interaction of vitamin D with other indices of mineral metabolism.

Asked to comment, Michal Melamed, MD, from the Albert Einstein College of Medicine in New York, said she was glad the authors looked at multiple bone minerals and not just vitamin D. "The sample size was small, but it is encouraging they still found an association."

Limitations

Dr. Melamed complimented the study but acknowledged that more work is needed. "This is a nice study, but it is still cross-sectional. We cannot establish a causal relationship and many questions remain regarding optimum vitamin D levels."

Dr. Melamed says she hopes some of these questions will be answered by the VITAL study. Also known as the Vitamin D and Omega-3 Trial, the research study is designed to include 20,000 men and women across the United States.

Investigators from Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts, are studying whether daily dietary supplements of vitamin D3 or omega-3 fatty acids reduce the risk for developing heart disease, stroke, and cancer in people who do not have a history of these illnesses. Recruitment began in January 2010 and is continuing through 2011.

This study was funded by the National Institutes of Health. Coauthor Dr. Tatjana Rundek reports receiving speaking fees from Bristol-Myers Squibb. The other authors have disclosed no relevant financial relationships.

Stroke. 2011;42:2240-2245. Abstract

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