Dietary fat in breast cancer survival.

Laboratory evidence suggests a plausible role for dietary fat in breast cancer pathophysiology. We conducted a systematic literature review to assess the epidemiological evidence on the impact of total dietary fat and fat subtypes, measured pre- and/or postcancer diagnosis, in relation to breast cancer-specific and all-cause mortality among breast cancer survivors. Studies were included if they were in English, had a sample size ≥200, and presented the hazard ratio/rate ratio for recurrence, disease-specific mortality, or all-cause mortality (n = 18). Although the results are mixed, most studies suggested that higher saturated fat intake prediagnosis was associated with increased risk of breast cancer-specific and all-cause mortality. Postdiagnostic trans fat intake was associated with a 45% and 78% increased risk of all-cause mortality. Higher monounsaturated fat intake before and after diagnosis was generally associated with increased risk of all-cause and breast cancer-specific mortality, albeit the majority of the studies were statistically nonsignificant. Two studies evaluating omega-3 fat intake suggested an inverse association with all-cause mortality. Although there were too few studies on fat subtypes to draw definitive conclusions, high consumption of saturated fat may exert a detrimental effect on breast cancer-specific and all-cause mortality, whereas omega-3 fat may be beneficial. The inconsistent and limited evidence warrants research to assess the impact of consumption of fat subtypes on breast cancer recurrence and mortality.