NEW ORLEANS - A major long-term study of more than 14,000 physicians showed no cardiovascular protection from vitamins E and C. Taken individually, these two antioxidant vitamins failed to protect against heart and blood vessel disease.
"We found no compelling evidence that either individual vitamin E or vitamin C reduces the risk of cardiovascular disease," said J. Michael Gaziano, M.D., M.P.H., principal investigator of the study and a cardiologist at Brigham and Women's Hospital and VA Boston Healthcare System in Boston, Mass.
Gaziano said results of the study add to the growing consensus about vitamin E's lack of cardiovascular protection based on several earlier trials that failed to find any effect.
The randomized, double-blind, placebo-controlled trial included 14,641 U.S. physicians 50 and older. Cardiovascular disease in the study included nonfatal heart attack, nonfatal stroke and fatal cardiovascular disease
Unlike several earlier studies in which vitamins E and C were often given as part of an antioxidant cocktail, this study investigated the two vitamins individually, said Howard D. Sesso, Sc.D., M.P.H., co-author and project director of PHS II and assistant professor of medicine at Brigham and Women's Hospital.
Antioxidant vitamins appeared promising in previous laboratory research and in observational human studies, in which people who reported eating a diet rich in vitamins E and C seemed to have fewer cardiovascular problems. The findings are an example of the importance of randomized clinical trials to test promising hypotheses generated by laboratory or observational research, Sesso said.
Fruits and vegetables may provide some protective effect beyond the vitamins they contain, or it could be that people who report eating a lot of fruits and vegetables have other characteristics that lead to better health.
Therefore, researchers needed a large, well-designed, placebo-controlled clinical trial that included a dedicated group of participants.
During an average eight years of follow-up, participants provided annual updates on compliance, various risk factors and health outcomes, allowing the investigators access to their medical records when necessary to confirm cardiovascular events or cause of death.
"Despite promising findings from laboratory research and observational studies, our results from PHS II point to the need for large-scale, long-term clinical trials testing the antioxidant hypothesism," Sesso said
The final arm of PHS II, testing daily multivitamin supplementation, is ongoing.