Beta carotene

 

A consistent body of evidence from clinical trials suggests that beta-carotene supplementation does not decrease the risk for lung, prostate, colon, breast, or non-melanoma skin cancer. Beta-carotene supplements were associated with an increased risk for lung cancer among smokers, especially heavy smokers, in 2 RCTs. Results from 4 RCTs demonstrate no reduced risk for cardiovascular events or mortality after beta-carotene supplementation.

Potential Harms of Vitamin Supplementation

There are several known adverse effects caused by excessive doses of vitamins; for example, moderate doses of vitamin A supplements may reduce bone mineral density, and high doses may be hepatotoxic or teratogenic. A small but significant increase in lung cancer mortality observed in trials of smokers has been ascribed to beta-carotene supplementation; adverse effects of beta-carotene supplementation on non-smokers have not been observed on other trials. The adverse effects of vitamin supplementation were not reported in most studies reviewed by the USPSTF. More studies are needed to better understand the harms of vitamin supplementation.

Source: U.S. Preventive Services Task Force. Routine Vitamin Supplementation to Prevent Cancer and Cardiovascular Disease: Recommendations and Rationale. June 2003. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/clinic/3rduspstf/vitamins/vitaminsrr.htm 

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