The retention and distribution by healthy young men of stable isotopes of selenium consumed as selenite, selenate or hydroponically-grown broccoli are dependent on the isotopic form

Twenty-seven healthy young men were randomly assigned to diets that supplie d low (32.6 mu g/d) or high (226.5 mu g/d) levels of selenium for a 105-d s tudy. After consuming the diets for 85 d, subjects were fed a test meal tha t contained Se-74 in the form of selenite or selenate and Se-82 incorporate d into hydroponically-raised broccoli. Urine, fecal and blood samples were collected daily. Isotope absorption was not different (P > 0.05) for selena te and Se in broccoli; Se absorption from selenite was highly variable and was not included in statistical analyses. Significantly more isotope was ab sorbed by subjects fed the high Se diet (P = 0.015), Urinary isotope excret ion was greater when selenate was fed than when broccoli was fed (P = 0.000 1), and consequently more Se from broccoli las compared to selenate) was re tained (59.2 +/- 2.4 and 36.4 +/- 4.6% for Se in broccoli and selenate, res pectively; P = 0.0001), Despite the higher retention, less isotope from bro ccoli than from selenate was present in the plasma. Plasma proteins separat ed by gel permeation chromatography showed that most of the isotopes were d istributed between two medium molecular weight peaks. Less isotope was foun d in plasma proteins of subjects fed the high Se diet, but the form of Se h ad no effect on isotope distribution. These results show that dietary Se in take alters the retention of stable isotopes of Se and that humans retain a nd distribute Se from broccoli in a different manner than Se from inorganic salts.