Formula feeding results in lower selenium status than breast-feeding or selenium supplemented formula feeding: a longitudinal study.

Thirty-two infants completely weaned by age 3.2 mo were randomized into two groups. Unsupplemented group was fed cow's milk-based liquid formula containing 3-5 micrograms Se/L. Se-supplemented group received the same formula supplemented with 20 micrograms Se/L. A third group consisted of exclusively breast-fed infants (51 at age 4 mo, 41 at 6 mo, 12 at 9 mo). Mean serum Se concentration in unsupplemented group decreased from 41 to 31 micrograms/L during the first 2 mo and remained constant until age 6 mo increasing gradually thereafter. In Se-supplemented group it increased steadily from 41 to 68 micrograms/L at age 6 mo and remained constant while supplemented formula was used. In breast-fed group it increased steadily until age 9 mo, between the levels of the two formula-fed groups, when it reached the concentration of Se-supplemented group. At age 12 mo no significant differences were present among the three groups.