Diet and breast cancer

The role of specific dietary factors in breast cancer causation is not completely resolved. Enthusiasm for the hypothesis that dietary fat intake was responsible for the high rates of breast cancer rates in western countries was based largely on the weakest form of epidemiologic evidence-correlations amongst countries. Results from prospective studies do not support the concept that fat intake in middle life has a major relation to breast cancer incidence during up to 14 years of follow-up. High energy intake in relation to physical activity, which accelerates growth and the onset of menstruation during childhood and leads to weight gain in middle life, contributes substantially to breast cancer risk. These effects of energy balance clearly account for an important part of international differences in breast cancer rates. Although the responsible constituents are not clear, some evidence suggests that low intake of vegetables modestly increases the risk of breast cancer. The possibility that specific carotenoids, or other compounds in these foods, are protective deserves further consideration. Alcohol intake is the best established specific dietary risk factor for breast cancer, and studies demonstrating that even moderate alcohol intake increases endogenous oestrogen levels provide a potential mechanism, thus supporting a causal interpretation. Recent findings suggest that adequate intake of folic acid may mitigate this adverse effect of alcohol. Hypotheses relating childhood and adolescent diet to breast cancer risk decades later will be more difficult to test in the near future unless novel data sources or methods for measuring diet in the distant past are developed, or unless radiographic, histological, or other markers of breast cancer risk are found and validated for use as intermediate markers of breast cancer. Nevertheless, available evidence is strong that breast cancer risk can be reduced by avoiding weight gain during adult years and limiting alcohol consumption. Recent evidence suggests that replacing saturated fat with olive oil may reduce risk of breast cancer, and this will decrease risk of coronary heart disease.