Rutherfurd Shane M, Fanning Aaron C, Miller Bruce J, Moughan Paul J
Riddet Institute, Massey University, Palmerston North, New Zealand; and
Fonterra Research and Development Centre, Palmerston North, New Zealand.
J Nutr. 2015 Feb;145(2):372-9. doi: 10.3945/jn.114.195438. Epub 2014 Nov 26.
The FAO has recommended replacing the protein digestibility-corrected amino acid score (PDCAAS) with the digestible indispensable amino acid score (DIAAS).
The objective of this study was to compare aspects underlying the calculation of the DIAAS and PDCAAS, including 1) fecal digestibility vs. ileal digestibility, 2) using a single nitrogen digestibility value for all amino acids, and 3) the effect of truncation. Truncated PDCAAS and untruncated DIAAS values calculated as formally defined were also compared and DIAAS data presented for 14 dietary protein sources.
Semisynthetic wheat starch-based diets were formulated to contain the test protein (as consumed by humans) source (whey- and soy-protein isolates, milk-, whey-, rice- and pea- protein concentrates, cooked kidney beans, roasted peanuts, cooked peas, corn-based breakfast cereal, cooked rice, cooked rolled oats, and wheat bran) as the sole nitrogen source and with an indigestible marker (titanium dioxide). Growing male rats (∼250 g bodyweight) were given a basal casein-based diet from day 1 to day 7 and then allocated (n = 6) to the test diets for day 8 to day 14 before ileal digesta were collected after the rats were killed. Total feces were collected from day 11 to day 14.
True fecal nitrogen digestibility was different (P < 0.05; 10% difference on average) from true ileal nitrogen digestibility for 11 of the 14 protein sources. True ileal nitrogen digestibility was different (P < 0.05) from true ileal amino acid digestibility for almost half of the indispensable and conditionally indispensable amino acids (differences ranged from 0.9% to 400%). DIAAS values ranged from 0.01 for a corn-based cereal to 1.18 for milk protein concentrate.
Untruncated PDCAAS values were generally higher than a DIAAS values, especially for the poorer quality proteins; therefore, the reported differences in the scores are of potential practical importance for populations in which dietary protein intake may be marginal.
联合国粮食及农业组织（FAO）建议用可消化必需氨基酸评分（DIAAS）取代蛋白质消化率校正氨基酸评分（PDCAAS）。
本研究的目的是比较DIAAS和PDCAAS计算背后的各个方面，包括：1）粪便消化率与回肠消化率；2）对所有氨基酸使用单一氮消化率值；3）截断的影响。还比较了按正式定义计算的截断PDCAAS值和未截断DIAAS值，并给出了14种膳食蛋白质来源的DIAAS数据。
配制以半合成小麦淀粉为基础的日粮，使其含有受试蛋白质（按人类食用量）来源（乳清蛋白和大豆分离蛋白、牛奶、乳清、大米和豌豆浓缩蛋白、煮熟的芸豆、烤花生、煮熟的豌豆、玉米早餐谷物、煮熟的大米、煮熟的燕麦片和麦麸）作为唯一氮源，并添加一种不可消化标记物（二氧化钛）。从第1天到第7天，给体重约250克的生长雄性大鼠喂食以酪蛋白为基础的基础日粮，然后在第8天到第14天分配到（n = 6）受试日粮组，大鼠处死后收集回肠食糜。从第11天到第14天收集总粪便。
14种蛋白质来源中的11种，其真实粪便氮消化率与真实回肠氮消化率不同（P < 0.05；平均差异10%）。几乎一半的必需氨基酸和条件必需氨基酸的真实回肠氮消化率与真实回肠氨基酸消化率不同（P < 0.05）（差异范围为0.9%至400%）。DIAAS值范围从玉米谷物的0.01到牛奶浓缩蛋白的1.18。
未截断的PDCAAS值通常高于DIAAS值，尤其是对于质量较差的蛋白质；因此，报告的评分差异对于膳食蛋白质摄入量可能处于边缘水平的人群具有潜在的实际重要性。
