Authors' objectives:

The purpose of this study was to conduct a systematic review of the scientific literature to identify and assess the evidence for the efficacy of the antioxidant supplements vitamin C, vitamin E, and coenzyme Q10 for the prevention and treatment of cardiovascular disease or modification of known risk factors for cardiovascular disease. It was our intention to perform meta-analyses where possible. The results may be used to develop a research agenda as well as to assist clinicians in advising patients who desire to take antioxidants to modify their risk of cardiovascular disease.

Authors' results and conclusions: Our literature search process identified 156 articles that represented results from 159 reports on 144 unique trials (i.e., those reporting data not duplicated in another publication). Of the 159 reports, one-third were judged to be of high quality using the Jadad method. Studies reporting on the outcomes of death, myocardial infarction, and/or blood lipid levels were selected for further analysis. For the interventions of vitamin E alone and in combination with other antioxidants, sufficient numbers of studies existed to perform pooled analysis. Both the pooled analyses of smaller studies and the results of larger studies did not show, in general, any beneficial effect of vitamin E supplementation on cardiovascular outcomes. Some trials reported beneficial effects on only one outcome or in subgroups, but these results were either not confirmed or were contradicted by other studies. We did not find evidence in the pooled analysis of smaller trials that vitamin E alone or in combination had a significant effect on levels of TC, LDL, or HDL. For the Heart Prevention Study, a small increase in LDL and HDL was reported. We identified one meta-analysis of the effect of coenzyme Q10 that reported mostly beneficial effects on measures of cardiac function in patients with heart failure. Five placebo-controlled, randomized studies that measured clinically relevant outcomes, enrolled at least 60 patients, and had at least 6 months duration of treatment were identified and reported mixed results. Four studies were identified that assessed the effect of vitamin C (mostly in combination with other antioxidants) on clinical outcomes in patients with or at high risk for cardiovascular disease using a placebo-controlled, randomized design, enrolling at least 60 patients, and having at least 6 months duration of treatment. The results were uniformly negative.

Authors' recommendations: For the combinations and conditions studied, the pooled analysis of smaller studies does not show evidence of an effect of vitamin E alone or in combination with other agents on all-cause mortality, cardiovascular mortality, fatal or nonfatal MI, or blood lipid levels. Results from a number of large clinical trials not included in the pooled analysis were substantially in agreement with this conclusion. Large studies of vitamin C in combination with other antioxidants for the prevention of cardiovascular disease reported no favorable outcomes. There is no convincing evidence either supporting or refuting the value of coenzyme Q10 in cardiovascular disease.

Authors' methods: Systematic review

Project Status: Completed

URL for project: http://www.ahrq.gov/clinic/tp/aoxcardtp.htm

Year Published: 2003

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: United States

Organisation Name: Agency for Healthcare Research and Quality

Contact Address: Center for Outcomes and Evidence Technology Assessment Program, 540 Gaither Road, Rockville, MD 20850, USA. Tel: +1 301 427 1610; Fax: +1 301 427 1639;

Contact Name: martin.erlichman@ahrq.hhs.gov

Contact Email: martin.erlichman@ahrq.hhs.gov

Copyright: Agency for Healthcare Research and Quality (AHRQ)