Selenium is an essential nutrient required for the correct function of the glutathione peroxidase enzyme. In this respect it is an important component in the reduction of hydrogen peroxide from tissues. In addition, selenium bonds to other proteins including the thioredoxin reductase and iodothyronine deiodinase enzymes as well as selenoprotein P. Mineral requirements increase during times of growth, and this is particularly true during the growth of infants, where body weight can double in a matter of months. Researchers have shown that infants and children have an increased requirement for selenium, and it is therefore no surprise that breast milk is rich in selenium and provides offspring with a high intake of the mineral. This is particularly important as glutathione peroxidise and plasma selenium levels are lower in newborns compared to the maternal concentrations.
However, formula fed infants do not fare so well. In fact compared to breast fed infants, formula fed infants have poorer selenium status. For example, in a comparisons of formula and breast fed infants1, mean serum selenium concentrations in cow’s milk based formula fed infants (consuming 5 µg selenium per day) decreased from 41 to 31 µg/L from 0 to 2 months of age and then remained constant until 6 months. Selenium concentrations in serum then rose slowly with the introduction of solid foods. In comparison, breast fed infants showed a steady rise of serum selenium concentrations from 41 µg/L to 68 µg/L over the same period. In addition, serum selenium rose quickly in formula fed infants supplemented with 20 µg/L selenium (to 68 µg/L) peaking at 2 months and remaining constant until 6 months of age.
Therefore cow’s milk formula fed infants may have significantly lower selenium status with regard serum concentrations, compared to breast fed infants. Supplementation of cow’s milk formula above that which the manufacturers provide raises the serum selenium to comparable levels with that in breast milk. The selenium concentrations of the umbilical sera of the mother’s was lower than reported in Germany and the United States, which likely reflects the lower intakes of the Finish Mothers. However, despite the possible poor selenium status of the maternal blood, the breast fed infants still maintained significantly higher selenium concentrations compared to formula fed infants. This supports other evidence that breast feeding is far superior to a formula based diet and suggests that cow’s milk formula is a poor source of selenium for growing infants.
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