Dietary fat, fat subtypes, and breast cancer risk: lack of an association among postmenopausal women with no history of benign breast disease.

A recent study among 13,707 postmenopausal women without benign breast disease (BBD) from the Breast Cancer Detection Demonstration Project (BCDDP) cohort found breast cancer risk associated with greater total fat, unsaturated fat, and oleic acid intake. We assessed the associations between cumulative averaged dietary intake from 1980, 1984, 1986, and 1990 with breast cancer risk through 1994 among 44,697 postmenopausal participants without BBD in the Nurses' Health Study (NHS). Multivariate Cox proportional hazard models, with age as the time variable, provided the estimated rate ratios (RRs) with 95% confidence intervals (CIs) from the 14 years of follow-up and the 1,071 breast cancer cases. In the Nurses' Health Study, breast cancer rates over the time period from 1980 to 1994 did not increase significantly with greater total fat [quintile (Q) 5 versus Q1 RR, 0.94; 95% CI, 0.77-1.15], saturated fat (RR(Q5 to Q1), 0.88; 95% CI, 0.70-1.12), unsaturated fat (RR(Q5 to Q1), 1.16; 95% CI, 0.92-1.46), oleic acid (RR(Q5 to Q1), 1.13; 95% CI, 0.81-1.57), linoleic acid (RR(Q5 to Q1), 0.93; 95% CI, 0.74-1.16), trans fatty acid (RR(Q5 to Q1), 0.9184; 95% CI, 0.73-1.13), or energy intake (RR(Q5 to Q1), 0.81; 95% CI, 0.67-0.99). A parallel analysis restricted to the same time period as the BCDDP study did not differ substantially. We found no increase in the rate of breast cancer with greater intake of dietary fat and fat subtypes among postmenopausal women without a history of BBD.