Bioavailability of selenium from meat and broccoli as determined by retention and distribution of 75Se

The concentration of selenium (Se), an essential nutrient, is variable in foods, depending, in part, on how and where foods are produced; some foods accumulate substantial amounts of Se when produced on high-Se soils. The chemical form of Se also differs among foods. Broccoli is a Se-accumulating plant that contains many methylated forms of Se, and Se bioavailability from broccoli has been reported to be low. Red meats such as pork or beef could accumulate Se when the animal is fed high-Se diets, and Se from such meats has been reported to be highly bioavailable for selenoprotein synthesis. In a further attempt to characterize the utilization of Se from broccoli and meats such as pork or beef, we have fed rats diets adequate (0.1 microg Se/g diet) in Se or high in Se (1.5 microg S/g diet), with the Se source being either high-Se broccoli or beef. Rats were then given test meals of broccoli or pork intrinsically labeled with 75Se. When dietary Se was nutritionally adequate (0.1 microg/g diet), more 75Se from pork than broccoli was retained in tissues; however, there were no significant differences in whole-body retention when dietary Se was high (1.5 microg/g diet). A significantly greater percentage of 75Se from broccoli than pork was excreted in the urine and dietary Se did not affect urinary excretion of broccoli 75Se, but the amount excreted from pork varied directly with dietary Se intake. Radiolabeled 75Se derived from pork effectively labeled selenoproteins in all tissues examined, but 75Se from broccoli was undetectable in selenoproteins. These differences in retention and distribution of Se from broccoli or pork are consistent with reported differences in bioavailability of Se from beef and broccoli. They also suggest that there are fewer differences in bioavailability when Se is consumed in supranutritional amounts.