The findings are an example of the importance of randomized clinical trials to test promising hypotheses generated by laboratory or observational research, Sesso said. 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.
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, Sesso said.
Therefore, researchers needed a large, well-designed, placebo-controlled clinical trial -- one that included a dedicated group of participants.
Each year, the investigators mailed participants calendar packs containing each vitamin or its placebo, depending upon the group to which each physician had been randomly assigned. The doses used in the study (400 international units of vitamin E every other day and 500 milligrams of vitamin C daily) correspond to typical amounts available commercially, Gaziano said.
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.
"Broadly speaking, there has been great interest in antioxidants in the prevention of cardiovascular disease," said Sesso. "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 hypothesis."
The final arm of PHS II, testing daily multivitamin supplementation, is ongoing.
Individual author disclosures are available on the abstract.
The study was funded by grants
|SOURCE American Heart Association|
Copyright©2008 PR Newswire.
All rights reserved