Comparison of estrone and 17β-estradiol levels in commercial goat and cow milk1

Increased levels of estrogen metabolites are believed to be associated with cancers of the reproductive system. One potential dietary source of these metabolites that is commonly consumed worldwide is milk. In North America, dairy cows are the most common source of milk; however, goats are the primary source of milk worldwide. In this study, the absolute concentrations of unconjugated and total (unconjugated plus conjugated) estrone (E1) and 17β-estradiol (E2) were compared in a variety of commercial cow milks (regular and organic) and goat milk. A lower combined concentration of E1 and E2 was found in goat milk than in any of the cow milk products tested. The differences in E1 and E2 levels between regular and organic cow milks were not as significant as the differences between goat milk and any of the cow milk products. Goat milk represents a better dietary choice for individuals concerned with limiting their estrogen intake.