Vitamin C may reduce hypertension risk.

Vitamin C may reduce hypertension risk

High blood levels of vitamin C may help ward off hypertension in healthy people, two new scientific studies suggest. If confirmed, the finding will add to this vitamin's growing renown as a dietary factor that may offer protection against cardiovascular diseases.

Scientists know that vitamin C, or ascorbic acid, can disarm chemicals called free radicals that form when the body uses oxygen (SN: 8/26/89, p.133). Free radicals can damage healthy cells, including the endothelial cells that take part in artery constriction and relaxation. Some scientists speculate that such injury may lead to hypertension -- a condition in which arteries remain constricted -- and may initiate the buildup of artery-clogging deposits, or atherosclerosis.

Now, two research teams working independently report that vitamin C seems to play a role in keeping blood pressure healthy. Both groups presented their findings this week at the the annual meeting of the American Society for Clinical Nutrition, held in Washington, D.C.

In one study, Leslie Cohen and Elaine B. Feldman at the Medical College of Georgia in Augusta and their colleagues looked at 67 healthy men and women aged 20 to 69 with normal blood pressure readings. They discovered that people in the group with the highest blood levels of ascorbic acid (about 102 micromoles per liter) had significantly lower blood pressure values than people with the lowest ascorbic acid levels (about 23 micromoles per liter). The scientists found a mean blood pressure reading of 104/65 millimeters of mercury for high-vitamin-C participants, compared with 111/73 for low-vitamin-C participants. Feldman points out that all volunteers had ascorbic acid blood levels within the normal range and obtained their vitamin C through diet alone.

In a second report, Elaine S.K. Choi at Tufts University in Boston and her colleagues looked at 241 elderly Chinese-Americans, some of whom had high blood pressure. They found that participants with the highest blood levels of ascorbic acid tended to have the lowest blood pressure values in the group.

The new results raise the intriguing possibility that vitamin C may lower blood pressure in people with established hypertension, comments David L. Trout at the U.S. Department of Agriculture in Beltsville, Md. Trout's own study of 12 people with borderline hypertension suggests that a daily 1-gram vitamin C supplement might reduce systolic (heart-contracted) blood pressure, but this preliminary, unpublished result awaits confirmation, he says.

Choi agrees that further research is needed to establish vitamin C's ability to prevent or treat hypertension. In the meantime, she and Feldman say that adding more vitamin-C-rich vegetables and fruits to a balanced diet can't hurt. As for vitamin supplements, Feldman cautions that popping too many vitamin C tablets (more than 1 gram per day) can cause adverse side effects, including kidney stones.