This study tested the hypothesis that during treatment of kwashiorkor (including marasmic kwashiorkor) with infection there is a lower rate of amino acid oxidation when the dietary intake of amino acids resembles the amino acid composition of acute phase proteins (APPs). Twenty-two children in Blantyre, Malawi, with kwashiorkor and acute infection were fed an isoenergetic, isonitrogenous diet with either egg white or milk as a protein source. The whole-body amino acid oxidation rate was measured after 24 h by determining the plasma urea rate of appearance, and whole-body protein breakdown and synthesis rates were determined from the plasma leucine rate of appearance. Plasma concentrations of C-reactive protein, alpha1-antitrypsin, tumor necrosis factor alpha (TNF-alpha), and interleukin 6 (IL-6) were determined on admission and at 24 and 48 h. The 11 children who received milk had a lower rate of amino acid oxidation than the children who received egg white (x +/- SD: 137 +/- 65 compared with 195 +/- 66 micromol urea x kg body wt(-1) x h(-1), P < 0.05). No significant differences were found between the two groups in the rate of whole-body protein breakdown or protein synthesis. The TNF-alpha concentration correlated inversely with whole-body protein breakdown and synthesis rates, and the IL-6 concentration correlated directly with C-reactive protein. We conclude that by making the amino acid composition of the diet resemble that of APPs in the treatment of acute kwashiorkor, the rate of amino acid oxidation can be decreased.