Estrone and 17β-estradiol concentrations in pasteurized-homogenized milk and commercial dairy products

Some individuals fear that estrogens in dairy products may stimulate growth of estrogen-sensitive cancers in humans. The presence of estrone (E1) and 17β-estradiol (E2) in raw whole cow's milk has been demonstrated. The objectives of this study were to determine if pasteurization-homogenization affects E2 concentration in milk and to quantify E1 and E2 concentrations in commercially available dairy products. The effects of pasteurization-homogenization were tested by collecting fresh raw milk, followed by pasteurization and homogenization at 1 of 2 homogenization pressures. All treated milks were tested for milk fat globule size, percentages of milk fat and solids, and E2 concentrations. Estrone and E2 were quantified from organic or conventional skim, 1%, 2%, and whole milks, as well as half-and-half, cream, and butter samples. Estrone and E2 were quantified by RIA after organic solvent extractions and chromatography. Pasteurization-homogenization reduced fat globule size, but did not significantly affect E2, milk fat, or milk solids concentrations. Estrone concentrations averaged 2.9, 4.2, 5.7, 7.9, 20.4, 54.1 pg/mL, and 118.9 pg/g in skim, 1%, 2%, and whole milks, half-and-half, cream, and butter samples, respectively. 17β-Estradiol concentrations averaged 0.4, 0.6, 0.9, 1.1, 1.9, 6.0 pg/mL, and 15.8 pg/g in skim, 1%, 2%, whole milks, half-and-half, cream, and butter samples, respectively. The amount of fat in milk significantly affected E1 and E2 concentrations in milk. Organic and conventional dairy products did not have substantially different concentrations of E1 and E2. Compared with information cited in the literature, concentrations of E1 and E2 in bovine milk are small relative to endogenous production rates of E1 and E2 in humans.