Postprandial metabolic utilization of wheat protein in humans

• Published in: The American journal of clinical nutrition 2005, Vol.81 (1), p.87-94
• Main Authors: Bos, C, Juillet, B, Fouillet, H, Turlan, L, Dare, S, Luengo, C, N'tounda, R, Benamouzig, R, Gausseres, N, Tome, D
• Format: Article
• Language: English
• Subjects: Adult; Biological and medical sciences; Biological Availability; Dietary Proteins - metabolism; digestible protein; Digestion; Edible Grain; Feeding. Feeding behavior; Female; Food and Nutrition; Fundamental and applied biological sciences. Psychology; Humans; Intestine, Small - metabolism; Life Sciences; Male; Metabolism; Nitrogen - metabolism; plant source protein; Postprandial Period; postprandial state; protein composition; protein value; Proteins; urea; Urea - metabolism; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Wheat; wheat protein
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/81.1.87

Background: The quality of cereal protein has been little studied in humans despite its quantitative importance in the diet, particularly in developing countries. Objective: The objective of this study was to determine the nutritional value of wheat protein in humans as assessed by the measurement of their real ileal digestibility and postprandial retention. Design: Healthy young adults (n = 14) were fitted with an intestinal tube to allow the collection of intestinal fluid in the duodenum or terminal ileum. Subjects received a mixed meal of 136 g wheat toast that contained 24.6 g uniformly and intrinsically 15N-labeled wheat protein. Intestinal fluid, blood, and urine were collected for 8 h postprandially. Results: The real ileal digestibility of dietary wheat nitrogen amounted to 90.3 +/- 4.3%. The cumulative amount of dietary nitrogen transferred to the deamination pools reached a plateau at 8 h of 24.7 +/- 6.8% of the amount ingested. The urinary excretion of dietary nitrogen in ammonia was high (0.8 +/- 0.3% of ingested dose). The incorporation of dietary nitrogen into serum protein reached 7.0 +/- 1.9% of the meal. Postprandial wheat protein retention was 66.1 +/- 5.8%. Conclusions: Our results show that wheat proteins had the same true ileal digestibility as did most of the plant proteins already studied in humans, but also that they had a lower postprandial nitrogen retention value. However, this low value was higher than that predicted from the calculation of indispensable amino acid scores, ie, 89% rather than 30-40% of the nutritional value of milk proteins.