Campbell Wayne W, Johnson Craig A, McCabe George P, Carnell Nadine S
Department of Foods and Nutrition, Purdue University, West Lafayette, IN 47907, USA.
Am J Clin Nutr. 2008 Nov;88(5):1322-9. doi: 10.3945/ajcn.2008.26072.
For older men and women, the Estimated Average Requirement (EAR) and Recommended Dietary Allowance (RDA) for protein are not known with confidence. Data from the limited research studies available suggest that the EAR and RDA might be greater than the assumed 0.66 and 0.80 g protein x kg body wt(-1) x d(-1), respectively.
This study assessed the effect of age on the EAR and RDA for protein.
Twenty-three younger (age: 21-46 y; 11 men, 12 women) and 19 older (age: 63-81 y; 8 men, 11 women) persons completed three 18-d trials with protein intakes of 0.50, 0.75, and 1.00 g protein x kg body wt(-1) x d(-1). Nitrogen balance was determined by using data from total nitrogen analyses of duplicate food composites and complete urine and feces collections from days 14 to 17 of each trial. Each subject's protein requirement was estimated by using linear regression of protein intake and nitrogen balance data from all 3 trials and inverse prediction.
The mean (+/- SD) protein requirement was not different between the younger and older subjects: 0.61 +/- 0.14 compared with 0.58 +/- 0.12 g protein x kg body wt(-1) . d(-1). On the basis of individual requirement estimates from the younger and older subjects combined (2.5% trimming from each tail and variation estimated by the bootstrap), an adequate protein allowance for these subjects was calculated to be 0.85 +/- 0.21 g protein x kg body wt(-1) x d(-1).
These short-term nitrogen balance results suggest that the requirement for total dietary protein is not different for healthy older adults than for younger adults and that the allowance estimate does not differ statistically from the RDA.
对于老年男性和女性，蛋白质的估计平均需求量（EAR）和推荐膳食摄入量（RDA）尚无确切定论。现有有限研究的数据表明，EAR和RDA可能分别高于假定的0.66和0.80克蛋白质×千克体重⁻¹×天⁻¹。
本研究评估年龄对蛋白质EAR和RDA的影响。
23名年轻人（年龄：21 - 46岁；11名男性，12名女性）和19名老年人（年龄：63 - 81岁；8名男性，11名女性）完成了三项为期18天的试验，蛋白质摄入量分别为0.50、0.75和1.00克蛋白质×千克体重⁻¹×天⁻¹。通过对每个试验第14至17天重复食物复合物的总氮分析以及完整尿液和粪便收集数据来测定氮平衡。使用所有三项试验的蛋白质摄入量和氮平衡数据的线性回归以及反向预测来估计每个受试者的蛋白质需求量。
年轻人和老年人的平均（±标准差）蛋白质需求量无差异：分别为0.61±0.14和0.58±0.12克蛋白质×千克体重⁻¹×天⁻¹。根据年轻人和老年人综合的个体需求量估计值（两端各去除2.5%并通过自展法估计变异），计算出这些受试者的充足蛋白质摄入量为0.85±0.21克蛋白质×千克体重⁻¹×天⁻¹。
这些短期氮平衡结果表明，健康老年人对膳食总蛋白质的需求量与年轻人无异，且摄入量估计值与RDA在统计学上无差异。
