Commentary: fat and breast cancer: time to re-evaluate both methods and results?

International comparisons, comparisons within countries, time trends within countries, case–control studies, and animal studies are all consistent with a positive relationship between incidence of breast cancer and fat consumption. 1 Cohort studies are normally considered free of the bias that potentially affect case–control studies, but, in contrast to expectations that a relationship would be confirmed, reports of pooled cohort data show no relation between total or types of fat intake and breast cancer risk. 2 In a summary of the prospective studies relating fat to breast cancer risk, it was concluded that there was moderate evidence to conclude that total fat in adult life ‘does not influence’ the risk of breast cancer independently of BMI, 1