Metabolic effects of a protein-supplemented carbohydrate drink in marathonrunners

A field study was performed to investigate the acute influence of a milk pr otein hydrolysate supplemented drink (CHO+PRO) on metabolism during and aft er a marathon run compared to the same drink without protein (CHO). Carbohy drate metabolites and hormones were not influenced by CHO+PRO. Levels of pl asma free fatty acids were significantly lower and levels of urea and most amino acids were significantly higher with CHO+PRO. Sweat urea and ammonia nitrogen excretion during the run as well as urinary 3-methylhistidine excr etion during the entire exercise day was similar with both treatments. Urin ary total nitrogen was significantly increased and urinary pH decreased wit h CHO+PRO. It was concluded that the supplemented protein was absorbed and probably at least partially oxidized during the run and that no obvious neg ative metabolic effects occurred. CHO+PRO did not acutely affect myofibrill ar protein breakdown as assessed by the 3-methylhistidine method; however, total body protein breakdown was not measured.