gamma-Globulin level and dietary protein intake during the first year of life.
To investigate the possible causes of relatively low blood gamma-globulin levels (less than or equal to 0.5 gm/dl) during the first year of life, 287 patients less than 1 year of age who were suffering from mild diseases were studied retrospectively. They were divided into two groups, those with a gamma-globulin level less than 0.5 gm/dl and those with a gamma-globulin level greater than 0.5 gm/dl. By reconstructing the diets given, it was found that they had been receiving isocaloric diets that differed only in protein supply: patients with lower gamma-globulin levels received 2.9 gm/kg/day of protein and patients with higher gamma-globulin levels received 4.0 gm/kg/day. Fifty-five healthy subjects were studied prospectively during the first year of life on two isocaloric diets that differed only in their protein content: the first one supplied 2.5 gm/kg/day of protein and the second supplied 4.0 gm/kg/day. At approximately 5, 7, and 10 months of age, hemoglobin, total protein, albumin, globulins, immunoglobulins, and other common blood parameters were measured. Patients on the lower protein diet had a gamma-globulin concentration of less than or equal to 0.5 gm/dl and those on the higher protein diet had a gamma-globulin concentration of greater than or equal to 0.8 gm/dl. Immunoglobulin levels, particularly IgG, were lower in patients on the lower protein diet. The subjects with lower protein intake and lower levels of gamma-globulin and immunoglobulins showed significantly higher morbidity.