Relationship Between Protein Intake By One Meal And Urinary Urea Excretion In Young Male Humans

Protein requirement for athletes has been shown not to exceed 2 g/kg/day. Recently, the International Association of Athletics Federation indicates that more than 1.7 g/kg/day protein is not necessary for any athletes. However, little information is available on the upper limit protein for one meal. We hypothesized that urinary urea nitrogen excretion (UUNE) would rapidly increase when one‐meal protein intake has exceeded its upper limit. We thus evaluated the relationship between protein intake and UUNE whether or not an UUNE flexion point exist in male subjects engaged in routine physical training. Thirty‐one healthy males, 22.1 years (SD 2.1, range 19–27), body weight 72.5 kg (SD 14.0, range 57.5–111.8) participated in a 3‐consecutive‐day protocol including a weekend. During the study, the subjects were asked to maintain their routine training and diet. Dietary intake was recorded every day. Urine was collected to analyze urea nitrogen. Dietary protein intake was 100.5 g/day (SD 34.4, range 33.0–210.4) or 1.4 g/kg/day (SD 0.5, range 0.5–3.1). Maximum protein intake by one meal was 52.9 g/meal (SD 20.8, range 12.7–114.9) or 0.7 g/kg/meal (SD 0.3, range 0.2–1.7). UUNE was a function of protein intake, whereas no flexion point of UUNE was observed within the range of protein intake in the current study. These results suggest that the flexion point of UUNE may exist at higher protein intake than that of the present study.