Beta-carotene and lung cancer: a case study.
The conflicting evidence of the relation between beta-carotene and lung cancer in humans serves as a poignant case study with respect to what types of evidence are sufficient to support or change a nutrition recommendation. This article is a review of the available evidence of the relation between beta-carotene and lung cancer, including data regarding beta-carotene intake (from diet and supplements), beta-carotene biochemical status, and vegetable and fruit consumption, and a discussion of the role of this evidence in making nutrition recommendations. More than 30 case-control and cohort studies were conducted over many years in various populations and indicated that people who eat more vegetables and fruit, foods rich in carotenoids, and carotenoids (beta-carotene in particular), as well as those with higher blood beta-carotene concentrations, have a lower risk of lung cancer than those who eat fewer such foods or have lower beta-carotene concentrations. In contrast, the intervention results from large, controlled trials of beta-carotene supplementation do not support the observed beneficial associations or a role for supplemental beta-carotene in lung cancer prevention; instead, they provide striking evidence for adverse effects (ie, excess lung cancer incidence and overall mortality) in smokers. The findings require that caution be exercised in recommending supplemental beta-carotene, particularly for smokers, and argue against changing the vegetable-fruit recommendations in the direction of greater nutrient specificity. This case study of beta-carotene and lung cancer stresses the importance of having results from at least one, and preferably more, large, randomized intervention trial before public health recommendations concerning micronutrient supplementation are considered.
Albanes
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Cancer Prevention Studies Branch, Division of Clinical Sciences, National Cancer Institute, Bethesda, MD 20892-7058, USA. daa@nih.gov
D000975:Antioxidants / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D004032:Diet; D016021:Epidemiologic Studies; D005638:Fruit; D006801:Humans; D008175:Lung Neoplasms / Q000517:prevention & control*; D018673:Nutrition Policy; D016032:Randomized Controlled Trials as Topic; D014675:Vegetables; D019207:beta Carotene / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*
D000975:Antioxidants; D019207:beta Carotene