Prothro J
Department of Nutrition and Dietetics, Georgia State University, Atlanta 30303.
Ann N Y Acad Sci. 1989;561:143-56. doi: 10.1111/j.1749-6632.1989.tb20977.x.
This paper has reviewed changes in body composition and protein metabolism that are associated with aging. Body protein mass decreases. Rates of both muscle and whole-body protein turnover/kg body weight decrease, and the percentage of turnover contributed by muscle to whole-body turnover decreases with age. Total plasma proteins, albumin, prealbumin, transferrin and ceruloplasmin levels decline with age, and, in the case of albumin levels, the decline continues when young-old are compared with old-old. Protein requirement of the elderly appears to have been underestimated by the factorial method. Nitrogen balance studies indicate a minimum of 0.7 g protein/kg/day in one study. Several studies show 0.8 g, whereas other studies show negative nitrogen balance at this level. The recommended protein intake is 1 g protein/kg/day, and 12-14% of total calories should be provided by protein. The few nitrogen balance studies that attempted to determine essential amino acid requirements are limited and contradictory.
本文综述了与衰老相关的身体成分和蛋白质代谢的变化。身体蛋白质质量下降。肌肉和全身蛋白质周转率/千克体重均下降，且随着年龄增长，肌肉对全身周转率的贡献百分比降低。总血浆蛋白、白蛋白、前白蛋白、转铁蛋白和铜蓝蛋白水平随年龄下降，就白蛋白水平而言，与高龄老人相比，年轻老人的白蛋白水平仍持续下降。老年人的蛋白质需求似乎被析因法低估了。氮平衡研究表明，一项研究中老年人每天每千克体重至少需要0.7克蛋白质。多项研究显示为0.8克，而其他研究表明在此水平时氮平衡为负。建议蛋白质摄入量为每天每千克体重1克，蛋白质应提供总热量的12 - 14%。少数试图确定必需氨基酸需求的氮平衡研究有限且相互矛盾。
