Analysis of data from a long-running women’s health study indicates that supplementation with Vitamin C is associated with a lower risk for coronary heart disease than a low intake of the vitamin, according to an article in the July 16th issue of the Journal of the American College of Cardiology. The researchers based their analysis on information in diet questionnaires completed as part of the Nurses’ Health Study.

"Based on our data, modest amounts of vitamin C supplements may lower one's risk of coronary heart disease. Our study cannot provide conclusive evidence for a protective role nor can it exclude the possibility that the association may be due to some other health-seeking characteristic among vitamin C supplement users," said Stavroula K. Osganian, MD, lead author of the study.

Although it is biologically reasonable that the antioxidant properties of vitamin C could help protect against heart disease, previous studies have produced conflicting results. Osganian said the findings from the current study highlight the need for more rigorous trials.

"The inconsistent findings from the available observational studies emphasize the need for further evidence from well-designed, randomized clinical trials to help answer this question prior to public policy recommendations regarding the optimal intake of vitamin C or need for supplements," he said.

The researchers analyzed dietary and clinical information from 85,118 women enrolled in the Nurses’ Health Study, including 16 years of follow-up data. After adjustment for age, smoking, and a variety of other coronary risk factors, the researchers observed that vitamin C supplement use was associated with a 28-percent lower risk of coronary heart disease. However, the researchers note that the women in this study generally had a low risk of heart disease.

The median daily intake of vitamin C in the lowest group was 70 milligrams. By contrast, the median daily intake among women in the highest group was 10 times as much (704 milligrams). The U.S. Recommended Dietary Allowance of vitamin C for women is 75 milligrams per day.

"In terms of our study, our results do not support a role for megadoses of vitamin C to lower your risk of coronary heart disease. It should be noted however, that our study population of women is relatively well-nourished, therefore our results apply to such populations, and our study only examines risk of coronary heart disease. The amount of vitamin C needed to prevent other adverse health outcomes, cancer for example, or the amount needed in undernourished populations or special populations needs to be considered when making such public policy recommendations," Osganian said.

The current study did not reveal any statistically significant link between heart disease risk and the amount of vitamin C in diet alone. Osganian noted, however, that there was little difference between the highest and lowest reported intakes of vitamin C from diet alone.

In an editorial, Balz Frei, PhD, wrote that even well-designed trials may not fully answer questions about whether vitamin supplementation can prevent heart disease: "What we know with certainty, however, is that a healthy diet and lifestyle lowers the risk of coronary heart disease, and this is what we should advocate to coronary heart disease patients and healthy people alike. An additional multivitamin/multimineral supplement as 'health insurance' also is sensible advice, as may be a vitamin C supplement to help lower coronary heart disease risk."

Frei interpreted the data as an indication that vitamin C itself seems to have a protective effect, rather than simply being a marker of fruit and vegetable intake.