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.