Low-Fat Dietary Pattern and Risk of Invasive Breast Cancer

Abstract

The hypothesis that a low-fat dietary pattern can reduce breast cancer risk has existed for decades. Supported by early rodent experiments,¹ country-to-country comparisons linked higher dietary fat intake to breast cancer risk.² However, case-control and cohort studies have had mixed results. A meta-analysis³ of 12 international case-control studies reported a significant positive association between fat intake and breast cancer with relative risks of 1.00, 1.20, 1.24, 1.24, and 1.46 across total fat intake quintiles defined by one of the Canadian case-control studies. In contrast, an analysis⁴ of 7 Western cohort studies found no such association with relative risks of 1.00, 1.01, 1.12, 1.07, and 1.05 across energy-adjusted fat intake quintiles. A recent meta-analysis, including both case-control and cohort studies, comparing highest and lowest fat intake categories reported a relative risk for breast cancer of 1.13 (95% confidence interval [CI], 1.03-1.25).⁵ Such inconsistent results may reflect limitations of the dietary assessment methods used^6-8; a recent study reported a significant positive association of fat intake and postmenopausal breast cancer incidence only when diet was measured with food diaries rather than a food frequency questionnaire (FFQ) used in most analytic epidemiological studies.⁹