Nutritional evaluation of protein hydrolysate formulas in healthy term infants: plasma amino acids, hematology, and trace elements.

BACKGROUND

Protein hydrolysate formulas are used for infants with food allergy. Most studies of such formulas focus on their effect on allergy and rarely evaluate their capacity to provide normal nutritional status.

OBJECTIVE

We compared plasma aminograms, serum urea nitrogen, and trace element status in breastfed infants, infants fed hydrolysate formulas, and infants fed milk formula.

METHODS

From 6 wk to 6 mo of age, infants were breastfed or fed regular milk formula (RF), 1 of 2 casein-hydrolysate formulas (CH-1 or CH-2), or whey-hydrolysate formula (WH). Anthropometric measures were taken monthly, and blood samples were collected at 6 wk and 6 mo. Plasma amino acids, serum urea nitrogen, hematologic indexes, plasma zinc, and plasma copper were analyzed.

RESULTS

There were no significant differences in hemoglobin, serum transferrin receptor, copper, or zinc among groups. Serum ferritin was significantly lower in infants fed the CH formulas than in the other groups. Infants fed CH-2 had significantly higher serum urea nitrogen than did all other groups. Plasma threonine, valine, phenylalanine, methionine, and tryptophan were significantly higher in the hydrolysate formula groups than in the breastfed group. Plasma tyrosine was significantly lower in infants fed the CH formulas than in the breastfed group, whereas arginine was significantly higher in the WH group than in all other groups. Plasma proline was lower, whereas threonine and tryptophan were higher, in the WH group than in the CH groups.

CONCLUSIONS

The iron status of infants fed CH formula was lower than that of all other groups. The amounts of amino acids provided by hydrolysate formulas appear excessive compared with regular formula, which is reflected by high serum urea nitrogen (CH-2) and high plasma amino acid concentrations. A reduced and more balanced amino acid content of hydrolysate formulas may be beneficial.