Does Beta‐Carotene Supplementation Reduce (or Increase) Cancer Risk?

Abstract

Epidemiologic studies have been very consistent in showing that consumption of dietary fruits and vegetables is inversely related to risk of certain cancers, especially lung cancer. It has been suggested that carotenoids, particularly β‐carotene, are the chemopreventive agents. Four long‐term, large, randomized intervention trials have been conducted to test the effectiveness of β‐carotene supplementation on cancer risk. The Alpha‐Tocopherol, β‐Carotene Cancer Prevention (ATBC) Study tested daily supplementation with 20 mg β‐carotene and 50 mg α‐tocopherol in smokers. The β‐Carotene and Retinol Efficacy Trial (CARET) tested daily supplementation with 30 mg β‐carotene and 25,000 IU of retinyl palmitate in adults at high risk for lung cancer (smokers, asbestos‐exposed). The Physicians’ Health Study (PHS) tested supplementation with 50 mg β‐carotene on alternate days in adults, 11% of whom were smokers. The Linxian (Chinese) Study tested daily supplementation with 15 mg β‐carotene, 50 μg selenium, and 30 mg α‐tocopherol in vitamin‐ and mineral‐deficient adults. The ATBC and CARET studies reported that β‐carotene increased the incidence of lung cancer in high risk groups. The PHS showed no effect of β‐carotene supplementation on cancer incidence. The Chinese study reported a lower mortality of total cancers. These results suggest that supplementation with β‐carotene for the prevention of cancer may pose a risk in smokers and asbestos workers and is of little benefit in preventing cancer in well‐nourished populations. Health benefits are more likely from increasing consumption of fruits and vegetables, including those rich in carotenoids. ▪ Key Words: carotenoids, beta‐carotene, cancer