True Ileal Amino Acid Digestibility of Human Foods Classified According to Food Type as Determined in the Growing Pig

A Food and Agriculture Organization Expert Consultation recommended the use of digestible indispensable amino acid score (DIAAS) to evaluate protein quality of foods for humans. Calculation of DIAAS requires true ileal digestibility (TID) of amino acid (AA) values but currently insufficient data are available.

This study aims to generate in pigs TID of AA for a wide range of foods commonly consumed by humans and determine the range of differences in TID of AA among food types.

A standardized protocol was followed to determine TID of AA in 97 foods across 3 laboratories. Female pigs (25-100 kg during study, n ≥ 6) received foods for 7 d following a Youden Square design with ileal digesta collected via T-cannula on days 6-7. Endogenous AA losses were determined by feeding a protein-free diet. Foods, diets, and digesta were analyzed for nitrogen, AA, reactive lysine, titanium and dry matter. Foods were categorized into food types with the degree of variation within each food type evaluated using descriptive statistics.

The TID (mean of AA) ranged from 0.247 (apples) to 0.988 (beef tenderloin). The median TID of AA was high (mean of AA > 0.90) for foods categorized as dairy products, eggs, fish and seafood, isolates and concentrates, meat, nuts, plant-based burgers, soy products and wheat products. Food categories with median TID < 0.80 were baked products, fruit, pulses and seeds, and wheat bran cereal, yeast, and zein. Food categories with low variations between foods were fish and seafood (1% units), dairy products (3% units), and eggs (5% units), whereas categories with the greatest variation were grains (18% units), vegetables (16% units), seeds (14% units), and fruit (12% units). There was considerable variation in TID for individual AA both within and among foods.

The database with TID of AA of 97 foods generated by 3 laboratories using a standardized methodology can be utilized for protein quality evaluation.