Absorption, retention, and utilization of two forms of selenium given simultaneously as stable isotope tracers to lactating and nonlactating women

We investigated absorption, retention, and utilization of selenomethionine (SeMet) and selenite (SeO3) in 6 lactating and 6 nonlactating women, 2 to 3 mo postpartum, and 7 never pregnant women. Subjects were maintained on controlled diets for 3 wk. After 1 wk equilibration, subjects received simultaneous oral doses of 74Se L-SeMet and 76Se SeO3. Complete urine and fecal collections were made for 1 d prior to and 2 wk after isotope dosing. Lactating women collected milk samples from all feedings for 24 h before and 48 h after isotopes. Blood was collected from subjects before isotope dosing and 2,24, 168, and 336 h later. All samples were analyzed for natural Se, 74Se, and 76Se by isotope dilution mass spectrometry