Consolazio C F, Johnson H L, Nelson R A, Dramise J G, Skala J H
Am J Clin Nutr. 1975 Jan;28(1):29-35. doi: 10.1093/ajcn/28.1.29.
Two groups of men consumed two levels of protein (1.4 and 2.8 g/kg body weight) during a 40-day experimental period. Physical activity and the sweat rates were fairly high during the entire experimental phase. Urinary nitrogen excretions remained fairly constant for both groups during the training and heavy physical activity periods. Nitrogen balances were positive exclusive or inclusive of the daily sweat nitrogen losses showing nitrogen retention. The essentially unchanged blood hemoglobin and serum protein levels showed that the control group was receiving an adequate protein intake to maintain nitrogen equilibrium, under conditions of fairly heavy physical acitvity. Although others may have suggested some compensatory reductions in the urinary excretion of nitrogen under conditions of profuse sweating, our data have not supported these conclusions. It appears that sweat losses of nutrients become relevant in determining requirements and will increase in importance as sweat rates are increased. The data again demonstrate that the nutrient losses during profuse sweating consitute an error that could seriously invalidate the accuracy of metabolic balance studies. In this study, although the men did increase body protein stores and muscle mass with high-protein diets, the additional body protein did not enhance physiological work performance. It is suggested that in this sutdy 100 g of protein/day was adequate for men performing fairly heavy work.
两组男性在为期40天的实验期内摄入了两种水平的蛋白质（1.4克/千克体重和2.8克/千克体重）。在整个实验阶段，身体活动和出汗率都相当高。在训练和高强度体力活动期间，两组的尿氮排泄量都保持相当稳定。无论是否包括每日汗液氮损失，氮平衡均为正值，表明有氮潴留。基本未变的血红蛋白和血清蛋白水平表明，在相当高强度的体力活动条件下，对照组摄入了足够的蛋白质以维持氮平衡。尽管其他人可能曾提出在大量出汗的情况下，尿氮排泄会有一些代偿性减少，但我们的数据并不支持这些结论。看来，营养物质的汗液损失在确定需求方面变得很重要，并且随着出汗率的增加其重要性也会增加。这些数据再次表明，大量出汗期间的营养物质损失构成了一个误差，可能会严重影响代谢平衡研究的准确性。在本研究中，尽管男性通过高蛋白饮食增加了身体蛋白质储备和肌肉质量，但额外的身体蛋白质并没有提高生理工作表现。建议在本研究中，对于从事相当繁重工作的男性来说，每天100克蛋白质就足够了。
