The association between breast cancer and consumption of dairy products: a systematic review

Introduction: breast cancer is the most common cancer in women and its relationship with dietary factors particularly dairy products, has been investigated trough several studies but up to now there are still not enough results to confirm the association between breast cancer and dairy products. Objective: the purpose of this systematic review was to expand the number of systematic reviews that to date exist on the relationship between dairy products consumption and risk of breast cancer. A comprehensive search of the PubMed, Scopus and Embase was performed from September 2005 to September 2018 in which one case control and cohorts' studies were included. Results: Eighteen studies were finally selected for the review (10 case-control and 8 cohorts' studies). These studies reported several statistically significant associations (OR, HR, RR) between dairy product consumption and the risk of breast cancer. Seven case-control and four cohorts' studies showed that dairy product consumption was inversely associated with the risk of breast cancer, on the other hand, a positive association was found in two case-control and non- significant association was found between dairy product consumption and the risk of breast cancer in the remaining studies (one case-control and four cohorts' studies) Conclusion: Although an inverse association was observed in most studies, it's difficult to draw conclusions when the methodology methods to collect the dairy product intake and the servings or portions measurements were different in each study. On the other hand, not all studies used the same confounding variable to estimate risk.