Bell S J, Bistrian B R, Ainsley B M, Manji N, Lewis E J, Joyce C, Blackburn G L
Nutrition/Metabolism Laboratory, New England Deaconess Hospital, Boston, MA 02215.
J Am Diet Assoc. 1991 May;91(5):586-9.
Essential amino acids, found in abundance in high-quality dietary protein, are required daily by hospitalized patients and healthy persons to maintain the dynamic process of protein metabolism. One method for assessing dietary protein quality is by determining a diet's chemical score, ie, the ratio of a gram of the limiting amino acid in a test diet to the same amount of the corresponding amino acid in a reference diet (eg, whole-egg protein) multiplied by 100. This investigation used the chemical score to evaluate the protein quality of 9 parenteral and 17 enteral diets commonly used to feed hospitalized patients. Standard parenteral and enteral products (ie, formulas that had not been designed for patients with a specific disease state) had chemical scores that ranged from 46% to 70%. Limiting amino acids were either methionine (plus cysteine) or phenylalanine (plus tyrosine). Products designed for patients with renal failure had the highest scores, which ranged from 85% to 145%. Products that were enriched with branched-chain amino acids for trauma patients had scores that ranged from 38% to 73%. The only product available for patients with pulmonary compromise had a score of 50%. The lowest scores, which ranged from 5% to 13%, were found in products for patients with hepatic failure. All products, except those with chemical scores below 13%, may be fed in relatively small amounts of protein (7 to 33 g) to satisfy the minimum daily requirements of essential amino acids, although such levels would not meet minimal daily nitrogen requirements. We recommend that dietitians use the chemical score to assess the protein quality of parenteral and enteral diets.
优质膳食蛋白质中富含必需氨基酸，住院患者和健康人每日都需要这些氨基酸来维持蛋白质代谢的动态过程。评估膳食蛋白质质量的一种方法是确定饮食的化学评分，即测试饮食中一克限制氨基酸与参考饮食（如全蛋蛋白）中相同数量的相应氨基酸的比例乘以100。本研究使用化学评分来评估9种常用的肠外营养制剂和17种肠内营养制剂的蛋白质质量。标准的肠外和肠内产品（即未针对特定疾病状态患者设计的配方）的化学评分范围为46%至70%。限制氨基酸为蛋氨酸（加半胱氨酸）或苯丙氨酸（加酪氨酸）。为肾衰竭患者设计的产品得分最高，范围为85%至145%。为创伤患者添加支链氨基酸的产品得分范围为38%至73%。唯一可用于肺部功能不全患者的产品得分为50%。得分最低的产品是为肝功能衰竭患者设计的，范围为5%至13%。除化学评分低于13%的产品外，所有产品都可以以相对少量的蛋白质（7至33克）喂养，以满足必需氨基酸的每日最低需求，尽管这样的水平不能满足每日最低氮需求。我们建议营养师使用化学评分来评估肠外和肠内营养制剂的蛋白质质量。
