A Meta-analysis of Fat Intake, Reproduction, and Breast Cancer Risk: An Evolutionary Perspective

Objectives: This study is a systematic review of literature published up to May of 2010 aimed to identify relationships between dietary fat, and fat subtypes, with risk of breast cancer in women. Methods: Descriptive data, estimates of relative risk and associated 95% confidence interval (CI) were extracted from relative studies and analyzed using the random effects model of DerSimonian and Laird. Results: Cohort study results indicated significant summary relative risks between polyunsaturated fat and breast cancer (1.091, 95% CI: 1.001; 1.184). In case-control studies no association between fat and breast cancer was observed. Post-menopausal women indicated a significant association between total fat (1.042, 95ToCI: 1.013; 1.073), PUFA intake (1.22, 95% CI: 1.08; 1.381), and breast cancer. A non-significant inverse relation between intake of all fat types and breast cancer was identified in premenopausal women. Conclusions: These results support the idea that possible elevations in serum estrogen levels by an adult exposure to a high-fat diet would increase breast cancer risk. Furthermore, menopausal status was observed to affect women's risk of breast cancer. Higher risks of breast cancer were found in post-menopausal women consuming diets high in total fat and, polyunsaturated fats. Conversely, dietary fat appears to have preventative effects in pre-menopausal women. This study takes a transformative approach combining epidemiological, biomedical, and evolutionary theory to evaluate how biocultural variations in risk factors (i.e., diet and reproduction) affect the evolution of breast cancers. Am. J. Hum. Biol. 23:601-608, 2011. (C) 2011 Wiley-Liss, Inc.