Beta-Carotene and Chemoprevention of Cancer

Cancer is the second leading cause of mortality in the U.S., responsible for over 20% of the approximately two million total annual deaths (1). Treatment of cancer has provided and will continue to provide enormous benefits to some categories of affected individuals. At the same time, however, interventions that may prevent cancer in healthy individuals could, at least in theory, also afford great benefits to society as a whole. For example, a complete cure for acute leukemia, which accounts for several thousand of the approximately 400,000 total cancer deaths in the U.S. each year, would certainly be a remarkable breakthrough in medical research. In terms of public health impact, however, even a small reduction, on the order of 30%, in the development of epithelial cell cancers, which account for 90% of U.S. cancer deaths, due to dietary supplementation with micronutrients could conceivably prevent over 100,000 cancer deaths annually. With respect to known etiologies, cigarette smoking is the leading identified avoidable cause of cancer as well as mortality from all causes, accounting for about 30% of all deaths due to malignancy in the United States (2). Heavy alcohol consumption, which ranks second, is responsible for about 3% of cancer deaths. Recently, promising, but unproven, hypotheses have suggested that a substantial percentage of cancers may be preventable through dietary changes. Although diet has been postulated to account for as many as 35% of the annual deaths from cancer, which characteristics of diet, if any, increase or decrease the risk of cancer remains unclear (2).