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| health > story page |         |
Vitamin C: A possible treatment for high blood pressure
December 20, 1999
By Sarah Yang (WebMD) -- Vitamin C has been touted as a treatment for the common cold, gallbladder disease and blocked arteries. Too little in the diet can cause scurvy, a disease marked by bleeding around the gums and loose teeth. Now, a new study may further boost vitamin C's reputation with results that it may also reduce high blood pressure.
Researchers from the Boston University School of Medicine and Oregon State University studied 39 patients with mild to moderate hypertension. About half of the patients took daily doses of 500 mg of vitamin C, also known as ascorbic acid, while the other half took a placebo. After one month, the average blood pressure of patients who took vitamin C dropped significantly more than that of patients in the placebo group, or 9.1 percent compared to 2.7 percent, respectively. Patients who took vitamin C also had approximately twice the level of ascorbic acid in their blood as those in the placebo group.
The findings, published in this week's journal Lancet, could be explained by the ability of vitamin C to "improve the biologic activity of nitric oxide," said co-author Balz Frei, Ph.D., professor of biochemistry and director of the Linus Pauling Institute at Oregon State University. Blood vessels require nitric oxide to relax or dilate, Frei said. "If nitric oxide is impaired, you fail to relax the artery, and that can result in increased blood pressure." Frei said vitamin C might also work well in conjunction with current prescription anti-hypertension medications. Patients from both study groups continued taking their anti-hypertension medications during the trial. Whatever the mechanism, the reduction in blood pressure was "impressive," said Norman Kaplan, M.D., clinical professor of internal medicine at the University of Texas Southwestern Medical Center at Dallas and a leading expert in hypertension. Kaplan said previous studies have linked a decrease in blood pressure to higher levels of vitamin C in the blood. "It's a presumably non-dangerous approach [to reducing blood pressure], but my recommendation is to eat more fruits and vegetables rather than take supplements," he said. "Nature's best, and it's cheaper." Foods rich in vitamin C include citrus fruits, green peppers, broccoli, tomatoes and strawberries. The vitamin C dosage used in the study was more than eight times greater than the recommended daily allowance (RDA) of 60 mg for the adult diet, but smaller than some of the 2,000 to 10,000 mg megadoses many vitamin advocates recommend. The proper dosage of vitamin C in the diet has been a subject of much debate in the medical community. Eight months ago, researchers from the National Institutes of Health recommended raising the RDA for vitamin C to between 100 mg and 200 mg. At the same time, many health experts say doses greater than 200 mg are useless at best, and potentially harmful. In 1998, a widely publicized study in the journal Nature linked daily doses of 500 mg of vitamin C to DNA damage. The results and methodology of that study have since been criticized, but many medical experts remain skeptical about pumping up the intake of vitamin C. Alice Lichtenstein, D.Sc., a spokesperson for the American Heart Association and professor of nutrition at Tufts University, said she knows of no data to suggest amending the current guidelines for vitamin C. She also cautioned against shunning conventional blood pressure medications based upon the findings published in Lancet. "It's an interesting study, but it needs to be replicated with a more diverse population," she said. Frei agreed, stating that "a single study can never give you a final answer. We would like to see more, larger studies, and then we'd have more confidence to really recommend this to patients with hypertension."
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