Cow’s milk contains significant amounts of estrogens and other hormones. A scientist at the Harvard School of Public Health, explains that U.S. dairies utilize pregnant cows that excrete large amounts of pregnancy hormones in their milk. These bovine hormones may contribute to hormone-dependent cancers such as breast and testicular cancer. Davaasambuu points out that not much is known about the relation between hormones in milk and cancer, so there’s no need for undue worry. But she does suggest a simple precaution: drink skim milk. The hormones in milk bind to fat, so you can avoid most of them by choosing fat-free.