The intake of milk and dairy products has been related to a higher risk of breast and prostate cancers, due to their positive association with systemic levels of insulin-like growth factor 1 (IGF-1), insulin and estrogen signaling, which are implicated in the regulation of breast cancer stem cells (BCSCs), EMT, local migration and invasion, angiogenesis, and chemotherapy resistance. This evidence concerns the gene IGF1 and breast cancer.