Dietary fats and breast cancer risk

The more than 10-fold international variation in the incidence of breast cancer and changing rates of breast cancer in migrants from low to high risk countries suggest that a substantial proportion of breast cancers could be prevented through modifiable environmental factors.1 Armstrong and Doll showed a strong international correlation between national per capita fat consumption and breast cancer rates.2 This stimulated a plethora of epidemiological and laboratory studies, which culminated in the largest and most ambitious randomised trial of dietary fat reduction to prevent breast cancer, the Women’s Health Initiative (WHI).3

However, nearly four decades after Armstrong and Doll’s publication, the role of dietary fat in breast cancer is still unclear. In the linked meta-analysis (doi:10.1136/bmj.f3706), Zheng and colleagues investigate the association between intake of fish and n-3 polyunsaturated fatty acids (n-3 PUFAs) and the risk of breast cancer.4 Associations between dietary total or saturated fat and breast cancer have been inconsistent in prospective studies.5 6 WHI, which reduced total fat intake by 9% rather than the target 14%, reported a relative risk of 0.91 (95% confidence interval …