A Meta-Analysis of Studies of Dietary Fat and Breast Cancer Risk
We have carried out a meta-analysis to summarize quantitatively the large published literature on dietary fat in the etiology of breast cancer. The summary relative risk for the highest compared to the lowest level of intake for the 20 studies that examined fat as a nutrient was 1.15 (95% CI 1.05–1.25). Cohort studies had a summary relative risk of 0.96 (95% CI 0.80–1.15) and case control studies a relative risk of 1.21 (95% CI 1.10–1.34). The difference between cohort and case control results was entirely attributable to two of the four published cohort studies, the other two giving results similar to those of case control studies. Summary estimates of risk excluded unity for monounsaturated fat and saturated fat (case control studies only), but not for polyunsaturated fat. For the 17 studies that examined food intake, the summary relative risks were 1.22 (95% CI 1.09–1.37) for meat, 1.35 (95% CI 1.19–1.54) for milk, and 1.17 (95% CI 1.02–1.36) for cheese. Summary relative risks for total fat intake were generally higher in studies of higher quality, that adjusted for energy intake and risk factors, that employed population based comparison groups, and that were done in Europe.