Gammaglobulin level and soy-protein intake in early infancy.

39 normal full term infants were fed during the first four months of life with three different diets based on the same formula of heated soy-flour fortified with DL-methionine. Each diet supplied 100 kcal/kg/day and gave about 2.5 (11 infants), 4.0 (19 infants) or 5.5 (9 infants) g/kg/day or soy-protein. After four months, growth was slightly lower in infants fed 2.5 g/kg/day of protein but was similar in the other two groups. Haematological parameters were in the normal range in all three groups. Serum gammaglobulin and immunoglobulin levels increased with the increase of dietary protein. The highest levels of gammaglobulin (0.51 +/- 0.16 mg/100 ml) and IgG (463.13 +/- 210.17 mg/100 ml) were observed in infants fed 5.5 g/kg/day of soy-protein and were similar to those previously observed in infants fed 2.5 g/kg/day of cows-milk protein. Morbidity was reduced with the increase of serum gammaglobulin and immunoglobulins.