Fat and Protein Intake and Subsequent Breast Cancer Risk in Postmenopausal Women

The role of diet in the etiology of breast cancer has been extensively evaluated. Case-control studies generally support an association, while cohort studies have produced inconsistent results. This study, carried out on the ORDET cohort, is the first prospective Italian study to address the relation between diet and breast cancer. Female volunteers were recruited from 1987 to 1992 among residents of Varese Province, Northern Italy, an area covered by a cancer registry. A semiquantitative self-administered food questionnaire was completed by participants. After a mean 5.5 yr of follow-up, 56 cases of invasive breast cancer were identified among the 3,367 postmenopausal members; 214 controls were randomly chosen from the cohort, matched to cases for age, menopausal status at recruitment, recruitment center, and recruitment period. The adjusted odds ratios for the highest tertile of intake vs. the lowest were 3.47 [95% confidence interval (CI) = 1.43-8.44] for total fat, 3.78 (95% CI = 0.95-15.0) for animal protein, and 0.42 (95% CI = 0.18-0.95) for total carbohydrates. These findings indicate a significant positive association between total fat and animal protein and risk of breast cancer and an inverse association with carbohydrates and constitute new evidence for a role of diet in the etiology of breast cancer.