Chemoprevention of cancer: lessons to be learned from beta-carotene trials.
Observational studies indicate a lower incidence of chronic diseases, including various cancers and cardiovascular disease, related to higher intakes of carotenoid containing foods (fruits and vegetables). Beta-carotene, one of the large number of naturally occurring carotenoids, thus appears to actively participate in health. However, recent intervention trials indicate that beta-carotene supplements are not efficacious in the prevention of cardiovascular disease and major cancers occurring in well-nourished populations. In fact, supplemental beta-carotene appears to increase, rather than to reduce, lung cancer incidence and deaths from cardiovascular disease in current smokers and in asbestos exposed workers. In order to resolve these paradoxes, we need to better understand the underlying biology, identify interactions, develop mechanistic hypotheses and test them in clinical trials in humans. Until that time, we should confine any premature enthusiasm for chemopreventive supplementation.
Vainio
H
H
Division of Health Risk Assessment, National Institute of Environmental Medicine, Karolinska Institutet, S-171 77, Stockholm, Sweden. harri.vainio@imm.ki.se
D000975:Antioxidants / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D002318:Cardiovascular Diseases / Q000139:chemically induced / Q000517:prevention & control*; D018890:Chemoprevention / Q000009:adverse effects; D004032:Diet; D004305:Dose-Response Relationship, Drug; D006801:Humans; D009369:Neoplasms / Q000139:chemically induced / Q000517:prevention & control*; D019207:beta Carotene / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*
D000975:Antioxidants; D019207:beta Carotene