Background: The optimal form and dose of selenium supplementation required to achieve indicators of selenium status equivalent to those in breastfed infants are unclear.
Objective: The objective was to evaluate the effect of fortifying infant formula (6 microg Se/L) with 2 concentrations of selenate (7 and 15 microg/L) on biochemical indicators of selenium status and growth at 16 wk in term infants.
Design: A randomized dose-response trial was conducted in 3 groups of term infants fed formula with different selenium concentrations [6 microg/L, F+0 (control); 13 microg/L, F+7; and 21 microg/L, F+15] and in a parallel breastfed reference group (BF; 11 +/- 2 microg Se/L).
Results: One hundred sixty-one (47% males) infants completed the 16-wk study. Baseline plasma selenium was 0.3 +/- 0.1 micromol/L. At 16 wk, plasma selenium had increased in all groups (P < 0.001) and was greater (P < 0.01) in the F+7 and F+15 groups and lower (P < 0.05) in the F+0 group than in the BF group. Plasma glutathione peroxidase increased in the F+15 group, decreased in the F+0 group, and, at 16 wk, was lower in the F+0 group than in the other groups (all P < 0.05). Erythrocyte selenium and glutathione peroxidase decreased in all groups (P < 0.05), but the magnitude of the change was greater in the F+0 than in the F+15 group (P < 0.05). There was no effect of selenium supplementation on growth.
Conclusions: Selenate fortification of formula resulted in an increase in plasma indicators of selenium status relative to indicators observed in infants fed low-selenium-containing formula. Although the erythrocyte indicators decreased in all groups, the 21-microg/L dose (F+15 group) resulted in a smaller decrease and in higher erythrocyte selenium than did the standard formula. Supplementation of low-selenium formula to provide a net selenium concentration close to that found in the breast milk of US women (18 microg/L) may be justified.