Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 5, 1999
Publication Date: N/A
Interpretive Summary: Selenium is an essential nutrient that may have substantial health benefits when consumed in amounts greater than the Recommended Dietary Allowance (RDA). The potential benefits of selenium are dependent on the way the body utilizes it, and different chemical forms of selenium are utilized in different ways. In this study, we have compared the way the body uses selenium from an inorganic source (selenate) and the form of selenium that is in broccoli. Compared to selenate, selenium from broccoli was retained better by the body, primarily because less was eliminated through the urine. Even though selenium from broccoli was better retained than selenium from selenate, less selenium from broccoli was found in the plasma. The distribution of selenium between plasma proteins was not affected by its chemical form. These results emphasize that selenium utilization by the body depends on the form in which is consumed, and they further show that selenium from broccoli is utilized in a different manner than selenium from inorganic salts such as selenate. The potential health benefits of selenium from broccoli are being investigated further.
Technical Abstract: Thirty healthy young men were fed diets that supplied low (32.6 ug/d) or high (226.5 ug/d) dietary intakes of selenium. After consuming the diets for 85 days, they were fed a test meal that contained 74**Se in the form of selenite or selenate, and 82**Se incorporated into hydroponically raised broccoli. Urine fecal and blood samples were collected daily. Isotope absorption was not different for selenate and Se in broccoli, but much less Se from selenite was absorbed, and its absorption values were more variable. Significantly more isotope was absorbed by subjects fed the high Se diet. Urinary isotope excretion was much greater when selenate was fed than when broccoli was fed, and consequently more Se from broccoli (as compared to selenate) was retained (59.2+/-2.4 and 36.4+/-4.6% Se in broccoli and selenate, respectively). Despite the higher retention, less isotope from broccoli than from selenate was present in the plasma. Plasma proteins were separated by column chromatography which revealed that most of the isotopes were distributed between two medium molecular weight peaks. Less isotope was found in plasma proteins of subjects fed the high Se diet, but the form of Se had no effect isotope distribution. These results show that dietary Se intake alters the retention of stable isotopes of Se. They further show that humans retain and distribute Se from broccoli in a different manner than Se from inorganic salts.