The importance of protein intake in master marathon runners

•Protein intake is as important as carbohydrates during a marathon.•Higher protein intake is related to better marathon performance times.•Higher protein intake is related to a lower postrace reduction of lean body mass.•Higher protein intake is related to lower postrace changes of biochemical indices. The aim of this study was to investigate the relationships between protein intake (during the tapering period and the race), marathon performance, body composition, acute race-induced changes, and selected metabolic– and muscle damage–related blood biomarkers in recreational master runners. In 58 experienced master runners (58.28 y ± 1.07 y, 174.06 cm ± 0.72 cm, 78.51 kg ± 0.76 kg body mass, 21.38% ± 0.52% body fat, mean ± SEM), nutritional intake was evaluated 1 wk before the race and during the marathon. Body composition was evaluated before and 2 h after the race. Blood samples were collected at the same time points. Body fat and lean body mass (LBM) were significantly reduced after the marathon (P < 0.01; η2: 0.311–0.888). Significant negative correlations were observed between energy intake from carbohydrates and proteins (expressed per LBM), marathon performance, and race-induced changes of blood metabolic-muscle damage indices (P < 0.05; r: –0.522 to –0.789). Positive correlations were observed between energy from carbohydrates and proteins per LBM, and body mass and LBM changes (P < 0.05; r: 0.485–0.814). The specific contribution of protein intakes per LBM (beta coefficient: –0.789 to 0.615) on race-induced changes of body composition and blood markers was the same as that of carbohydrate intakes per LBM (beta coefficient: –0.777 to 0.559). Marathon-induced changes in body composition and metabolic blood indices are highly related to protein intake, either during the tapering period or during the race, with runners experiencing the lowest changes when consuming higher protein intakes.