Lee Swanson Research Update

Vitamin D Linked to Heart Health in Men

July 2011

Increased intakes of vitamin D are associated with a reduced risk of cardiovascular disease in men, suggest new findings from a Harvard-led study.

Men who met the Dietary Reference Intake (DRI) of vitamin D of at least 600 IU per day had an associated risk of developing cardiovascular disease (CVD) that was 16% lower than men with a daily intake of less than 100 IU, according to findings published in the American Journal of Clinical Nutrition.

Unexpectedly, no such association was observed in women, which may be related to the doses, added researchers from Harvard School of Public Health (HSPH), the University of Massachusetts-Boston, Brigham and Women’s Hospital and Harvard Medical School.

"Because of the connection between sun exposure and skin cancer, avoidance of direct sun exposure and use of sun protection in outdoor activities have been recommended," wrote the researchers, led by Qi Sun, a research associate in HSPH’s Department of Nutrition.

"Increasing vitamin D intake from foods or supplements, therefore, becomes one important measure to maintain optimal vitamin D status for persons who do not receive enough sun exposure.

"The current investigation provides the first evidence supporting potential benefits of moderate intake of vitamin D on CVD risk in men, whereas no associations were observed in women," they added.

Vitamin D refers to two biologically inactive precursors: D3, also known as cholecalciferol, and D2, also known as ergocalciferol. Both D3 and D2 precursors are transformed in the liver and kidneys into 25-hydroxyvitamin D (25(OH)D)—the non-active "storage" form—and 1,25-dihydroxyvitamin D (1,25(OH)2D)—the biologically active form that is tightly controlled by the body.

While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that some people’s bodies make no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.

Vitamin D deficiency in adults is reported to precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, infectious diseases, cardiovascular diseases and more.

The new study supports the potential heart health benefits for men. The Boston-based scientists analyzed data from 74,272 women and 44,592 men, none of whom had CVD at the start of the study.

At the end of the study, 9,886 cases of coronary heart disease and stroke were documented. A 16% reduction was observed for men who met the DRI, compared to men with daily intakes of less than 100 IU, but no such benefits were observed in women.

Commenting on the potential mechanism, the researchers said that vitamin D may influence the reninangiotensin system (linked to blood pressure regulation), function of the endothelium (the cells lining blood vessels), insulin resistance and systemic inflammation. "These mechanisms may explain the inverse association between vitamin D intake and CVD risk in men," they said.

For the women, however, the researchers said the result was "unexpected" but consistent with previous studies and this is perhaps linked to a low dose of vitamin D being used.

"Additional studies are warranted before a firm conclusion regarding the effects of vitamin D intake or supplements on CVD outcomes can be made," they said.

"Nonetheless, a large trial that examines the effects of high-dose vitamin D supplementation (2,000 IU/d) on the primary prevention of CVD and other chronic diseases is being conducted."

American Journal of Clinical Nutrition; Published online ahead of print.

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