Mitchell Cameron J, Milan Amber M, Mitchell Sarah M, Zeng Nina, Ramzan Farha, Sharma Pankaja, Knowles Scott O, Roy Nicole C, Sjödin Anders, Wagner Karl-Heinz, Cameron-Smith David
Liggins Institute, The University of Auckland, Auckland, New Zealand.
Food Nutrition & Health Team, Food.
Am J Clin Nutr. 2017 Dec;106(6):1375-1383. doi: 10.3945/ajcn.117.160325. Epub 2017 Nov 1.
The Recommended Daily Allowance (RDA) for protein intake in the adult population is widely promoted as 0.8 g · kg · d Aging may increase protein requirements, particularly to maintain muscle mass. We investigated whether controlled protein consumption at the current RDA or twice the RDA (2RDA) affects skeletal muscle mass and physical function in elderly men. In this parallel-group randomized trial, 29 men aged >70 y [mean ± SD body mass index (in kg/m): 28.3 ± 4.2] were provided with a complete diet containing either 0.8 (RDA) or 1.6 (2RDA) g protein · kg · d, aimed to balance energy needs. Before treatment and after 10 wk of intervention, whole-body and appendicular lean mass were measured by using dual-energy X-ray absorptiometry. Knee-extension peak power was measured with dynamometry. Both groups were found to have been in a moderate negative energy balance (mean ± SD RDA: 209 ± 213 kcal/d; 2RDA 145 ± 214 kcal/d; 0.427 for difference between the groups). In comparison with RDA, whole-body lean mass increased in 2RDA ( = 0.001; 1.49 ± 1.30 kg, < 0.001 compared with -0.55 ± 1.49 kg, = 0.149). This difference was mostly accounted for by an increase in trunk lean mass found in 2RDA (+1.39 ± 1.09 kg, < 0.001). Appendicular lean mass also decreased in RDA compared with 2RDA ( = 0.022), driven by a reduction in RDA (-0.64 ± 0.91 kg, = 0.005 compared with 0.11 ± 0.57 kg, = 0.592). Adjusting for energy imbalances did not alter these findings. Knee-extension peak power was also differently affected ( = 0.012; 26.6 ± 47.7 W, = 0.015 in 2RDA compared with -11.7 ± 31.0 W, = 0.180 in RDA). Consumption of a diet providing 2RDA for protein compared with the current guidelines was found to have beneficial effects on lean body mass and leg power in elderly men. These effects were not explained by differences in energy balance. This trial was registered at the Australia New Zealand Clinical Trial Registry (www.anzctr.org.au) as ACTRN12616000310460.
成人蛋白质摄入量的推荐每日摄入量（RDA）被广泛宣传为0.8克·千克·天。衰老可能会增加蛋白质需求，尤其是为了维持肌肉质量。我们研究了按照当前RDA或两倍RDA（2RDA）控制蛋白质摄入量是否会影响老年男性的骨骼肌质量和身体功能。在这项平行组随机试验中，为29名年龄大于70岁[平均±标准差体重指数（千克/米²）：28.3±4.2]的男性提供了完整饮食，其中蛋白质含量分别为0.8（RDA）或1.6（2RDA）克·千克·天，旨在平衡能量需求。在治疗前和干预10周后，使用双能X线吸收法测量全身和四肢瘦体重。用测力计测量膝关节伸展峰值功率。发现两组均处于中度负能量平衡状态（平均±标准差RDA组：209±213千卡/天；2RDA组：145±214千卡/天；两组之间差异的P值为0.427）。与RDA组相比，2RDA组的全身瘦体重增加（P = 0.001；增加1.49±1.30千克，与RDA组减少0.55±1.49千克相比，P < 0.001，RDA组P值为0.149）。这种差异主要是由于2RDA组躯干瘦体重增加（增加1.39±1.09千克，P < 0.001）。与2RDA组相比，RDA组的四肢瘦体重也有所下降（P = 0.022），这是由RDA组的减少所致（减少0.64±0.91千克，与2RDA组增加0.11±0.57千克相比，P = 0.005，2RDA组P值为0.592）。对能量不平衡进行调整并没有改变这些结果。膝关节伸展峰值功率也受到不同影响（P = 0.012；2RDA组为26.6±47.7瓦，P = 0.015，而RDA组为 -11.7±31.0瓦，P = 0.180）。与当前指南相比，摄入提供2RDA蛋白质的饮食对老年男性的瘦体重和腿部力量有有益影响。这些影响无法用能量平衡差异来解释。该试验在澳大利亚新西兰临床试验注册中心（www.anzctr.org.au）注册，注册号为ACTRN12616000310460。
