Vitamin C's stretch.

Healthy blood vessels expand slightly with each pulse of blood pumped by the heart, and they temporarily stretch even more during bouts of exercise. This dilation occurs in response to nitric oxide produced by the vessels themselves. The nitric oxide-induced dilation diminishes in persons with coronary artery disease, but vitamin C supplements can help restore it, a new study finds.

A normal vessel can dilate up to 15 percent in diameter. Having found that a single, large dose of vitamin C can temporarily increase a vessel's ability to dilate appropriately, Joseph A. Vita of the Boston University School of Medicine and his colleagues wondered whether that responsiveness would persist after longer term and more moderate vitamin C supplementation. They gave 500 milligrams daily of either the vitamin or a placebo to 46 heart-disease patients.

In the June 29 CIRCULATION, the researchers report that vessels that initially dilated on average just 6.6 percent could, after a month of treatment, expand some 9 percent. No similar improvement resulted from the placebo. Vita suspects that vitamin C works by restoring the ability of a blunted vessel enzyme to produce nitric oxide.