A prospective study of diet and benign breast disease.

Much attention has been paid to the relation between diet and breast cancer risk. Because benign breast disease (BBD), particularly atypical hyperplasia (AH), is a marker of increased breast cancer risk, studies of diet and BBD may provide evidence about the effect of diet at an early stage in the process of breast carcinogenesis. We evaluated the relationship between fat, fiber, antioxidant and caffeine intake and incidence of non-proliferative BBD, proliferative BBD without atypia and AH in the Nurses' Health Study II. We calculated rate ratios (RR) and 95% confidence intervals (95% CI) for each quartile of energy-adjusted intake using the lowest quartile as reference. There was no increase in risk of BBD with increasing fat intake, rather increasing vegetable fat was associated with a significant reduction in the rate of proliferative BBD without atypia. There was no significant association between any type of BBD and micronutrient intake. High caffeine consumption was positively associated (RR = 2.46, 95% CI 1.11-5.49 for the highest quartile), and use of multivitamin supplements inversely associated (RR = 0.57, 95% CI 0.33-0.98) with risk of AH although these analyses were based on small numbers. These data do not support the hypothesis that higher fat consumption increases risk of BBD, with or without atypia, and also provide little evidence for a major role of antioxidants in the development of breast disease. They do, however, raise the possibility that high caffeine intake may increase, and use of vitamin supplements may decrease risk of developing AH.