Taking Vitamin Supplements To Prevent Cardiovascular Disease and Cancer: Recommendations from the U.S. Preventive Services Task Force

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The summary below is from the full reports titled "Routine Vitamin Supplementation To Prevent Cancer and Cardiovascular Disease: Recommendations and Rationale" and "Routine Vitamin Supplementation To Prevent Cardiovascular Disease: A Summary of the Evidence for the U.S. Preventive Services Task Force." They are in the 1 July 2003 issue of Annals of Internal Medicine (volume 139, pages 51-55 and pages 56-70). The first report was written by the U.S. Preventive Services Task Force; the second report was written by C.D. Morris and S. Carson.

What is the U.S. Preventive Services Task Force?

The U.S. Preventive Services Task Force (USPSTF) is a group of health experts that reviews published research and makes recommendations about preventive health care.

What is the problem and what is known about it so far?

Cardiovascular disease (CVD) and cancer are common problems for Americans. Shortages of antioxidant vitamins (vitamins A, C, and E; beta-carotene; and folic acid) are associated with the blood vessel changes that occur in CVD. Therefore, people have thought that taking these vitamins might reduce the chances of developing CVD. Similarly, information suggests that these vitamins might lower a person's chances of developing cancer. Many studies have examined associations between particular vitamins and CVD and cancer. The studies vary in quality, and their results often conflict.

How did the USPSTF develop these recommendations?

The USPSTF reviewed published studies to evaluate whether taking vitamins A, C, and E; beta-carotene; or folic acid (alone, in combination, or as part of a multivitamin tablet) lowers people's chances of developing CVD. The USPSTF rated the quality of each study to decide how heavily to weigh it in the recommendations. The review examining CVD appears in the 1 July 2003 issue of Annals of Internal Medicine. In addition, the USPSTF performed another review to see whether taking the same vitamins lowers a person's risk for cancer. This review is available from the Agency for Healthcare Research and Quality (http://www.preventiveservices.ahrq.gov).

What did the authors find?

The authors of the review on CVD found that the highest-quality studies did not show that vitamins consistently or meaningfully decreased CVD. The highest-quality studies assigned people at random to take either vitamin supplements or a placebo pill. Placebo pills looked like the vitamin but contained no active ingredients. In these types of studies, the groups of people are similar in all regards except for taking vitamins. A fair number of studies with weaker designs suggested an association between taking vitamins and less CVD. However, in the weaker studies, the people who took vitamins may have had healthier behavior in general, such as better eating and exercise habits. The authors of the article on vitamins and cancer found no convincing evidence that vitamins prevented cancer. In two high-quality studies, smokers taking beta-carotene supplements developed cancer more often than those who did not take beta-carotene.

What does the USPSTF suggest that patients do?

The USPSTF recommends that people do not take beta-carotene supplements to lower their chances of developing CVD or cancer. The USPSTF recommends neither for nor against taking vitamins A, C, or E; multivitamins with folic acid; or combinations of these vitamins for the primary purpose of preventing CVD or cancer.

What are the cautions related to these recommendations?

These recommendations focus only on preventing CVD or cancer. There may be other reasons that people choose to take vitamins. These recommendations do not apply to people who are known to have definite deficiencies of one of the vitamins studied.