Selenium absorption and retention from a selenite- or selenate-fortified milk-based formula in men measured by a stable-isotope technique

The present study was designed to determine the apparent absorption and ret ention of the inorganic Se compounds SeO32- and SeO42-, which are commonly used for Se fortification of clinical nutrition products and infant formula s. Ten healthy men were fed a milk-based formula labelled with 40 mug Se as (SeO32-)-Se-74 or (SeO42-)-Se-76 on two consecutive days using a randomise d crossover design. Se stable-isotope analysis of 9 d complete collections of urine and faeces was used to calculate apparent Se absorption and retent ion. Se retention from (SeO32-)-Se-74 (41.0 (SD 8.4) %) and from (SeO42-)-S e-76 (46.0 (SD 7.9) %) was not significantly different (P > 0.05). However, Se absorption was significantly higher from SeO42- than from SeO32- (91.3 (SD 1.4) % v. 50.2 (SD 7.8) %, P < 0.05). Urinary excretion of the administ ered dose was 9.2 (SD 1.8) % for (SeO32-)-Se-74 and 45.3 (SD 8.2) % for (Se O42-)-Se-76 (P < 0.05). Urinary Se excretion kinetics differed significantl y for the two Se compounds; 90 % of the total urinary Se was excreted after 121 h for (SeO32-)-Se-74 and after 40 h for (SeO42-)-Se-76 (P < 0.05). The se results suggest that although Se absorption and urinary excretion differ for SeO32- and SeO42-, both Se compounds are equally well retained when ad ministered at a relatively low dose (40 mug Se). The nutritional impact of Se fortification of foods would thus be expected to be similar when SeO42- or SeO32- are used.