American Journal of Clinical Nutrition, Vol. 69, No. 2, 344-345,
February 1999
© 1999 American Society for Clinical Nutrition
IARC Handbooks of Cancer Prevention: Carotenoids
David Heber
UCLA Center for Human Nutrition Warren Hall Laboratory 900 Veterans Avenue Room 12-217 Los Angeles, CA 90095 E-mail: dheber{at}med1.medsch.ucla.edu.
IARC Handbooks of Cancer Prevention: Carotenoids, by the IARC Working Group on the Evaluation of Cancer Preventive Agents, Vol 2, 1998, 326 pages, softcover, $135.00. Oxford University Press, Oxford, United Kingdom.
This is an outstanding book that addresses comprehensively the perennial question asked by the famous carrot-chomping cartoon rabbit, "Eh, what's up Doc ?" In fact, the many different carotenoids found in fruit and vegetables are a fascinating group of compounds with highly significant implications for nutrition at many levels. The book covers the chemical and physical characteristics of carotenoids and the commercial sources of, use and application of, analysis of, and human exposure to carotenoids. In addition, the metabolism of carotenoids, the kinetics and genetic variation of carotenoids in humans and other species, and the preventive and beneficial effects, the carcinogenicity, and other toxic effects of these compounds are also discussed. The book recommends that future research include investigation of better biomarkers, investigation of better animal models, more intervention studies, investigations of food composition, and studies to develop a better understanding of the metabolism of carotenoids and mechanisms of carcinogenesis. The discontinuation of 2 large clinical trials of ß-carotene supplementation—the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study and the Carotene and Retinol Efficacy Trial—left many questions unanswered when evidence was found that prospective ß-carotene supplementation increased the incidence of lung cancer in heavy smokers. The unexplained effect of ß-carotene was made more biologically plausible by the retrospective observation that the increased trend in new cancers could be traced linearly back to early times after exposure. The failure to observe a similar increase in cancer incidence after ß-carotene supplementation of healthy men in the Health Professionals Study cohort led to the hypothesis that the smokers' metabolism of carotenoids played a special role in cancer promotion, perhaps by converting antioxidant molecules to prooxidant molecules. These intervention-trial findings were in stark contrast with the epidemiologic findings that higher dietary intakes of ß-carotene and higher blood concentrations of ß-carotene were associated with a 20–50% decreased risk of lung cancer when persons with the highest concentrations were compared with persons with the lowest concentrations. How should carotenoid intakes from food be ensured or the diet supplemented when many populations clearly do not eat adequate amounts of fruit and vegetables? How do carotenoids interact with each other and with other antioxidants? For those interested in the chemistry, biology, and anticancer properties of carotenoids, this book is an excellent place to begin to explore the epidemiologic, animal science, human metabolism, and clinical intervention trial data in great detail. This book is suitable for postdoctoral fellows, professors, institutional libraries, and those in the government and industry who are interested in this important area of research.
