The relationship between fat and progesterone, estradiol, and chorionic gonadotropin levels in Quebec cow's milk

Purpose The majority of milk in industrialized countries is obtained from pregnant cows, which contains increased levels of estrogen and progesterone compared to non-pregnant cows. The aim of this study was to quantify the amount of hormones present in milk with different fat content because previous studies on humans have shown potential effects of increased milk consumption on serum and urine hormone levels as well as on sperm parameters. However, it is unclear whether consumption of milk at the currently recommended levels would lead to systemic effects. Methods Samples of cow's milk of varying fat concentrations (0, 1, 2, 3.25, 10, and 35%) were analyzed via competitive ELISA assays. Results Progesterone concentrations were significantly correlated to increasing fat content of milk (r = 0.8251, p = 0.04). Conclusions Research on conditions in which additional progesterone may have an effect on human health should consider inclusion of limitation of milk intake and its effects. Further studies are needed to determine the concentration of progesterone in milk of different fat content in other regions and countries and to quantify the potential pathophysiologic role.