Beta-Carotene and Lung Cancer: A Review of Randomized Clinical Trials.

Recent randomized clinical trials of supplemental beta-carotene as a chemopreventive agent against lung cancer have had contradictory results. This review examines the results and underlying rationale of these trials and discusses the contradictory findings. Increased lung cancer risk among smokers who received beta-carotene was observed in two of the four trials. The results indicate that beta-carotene supplementation is contraindicated among smokers. Ultimately, abstinence from smoking remains the best way to reduce lung cancer risk. The data linking beta-carotene to reduced cancer risk can be disputed because it is difficult to determine the beta-carotene content of foods and measure dietary beta-carotene intake. However, evidence that higher fruit and vegetable intake is consistently associated with reduced cancer risk at most sites remains unchallenged. This may indicate that a diet with adequate fruits and vegetables-not simply the consumption of a specific phytochemical-may be related to reduced cancer risk.