Abstract
BackgroundProtein quality evaluation aims to determine the capacity of food sources and diets to meet protein and indispensable amino acid (IAA) requirements. This study determined whether nitrogen balance was affected and whether dietary IAA were adequately obtained from the ad libitum consumption of diets at three levels of protein from different primary sources for 12 days.MethodsTwo 12-day randomized crossover design trials were conducted in healthy subjects [n = 70/67 (M/F); age: 19-70 y; BMI: 18.2-38.7 kg/m2]. The relative dietary protein content was lower than [5% of energy (En%)], similar to (15En%), and higher than (30En%) customary diets. These diets had a limited variety of protein sources, containing wheat protein as a single protein source (5En%-protein diet) or 5En% from wheat protein with 10En% (15En%-protein diets) or 25En% (30En%-protein diets) added from whey with α-lactalbumin, soy or beef protein.ResultsThere was a dose-dependent increase in nitrogen excretion with increasing dietary protein content, irrespective of the protein sources (P = 0.001). Nitrogen balance was maintained on the 5En%-protein diet, and was positive on the 15En%- and 30En%-protein diets (P < 0.001) over 12 days. Protein intake from the 5En%-protein diet did not reach the amount necessary to meet the calculated minimal IAA requirements, but IAA were sufficiently obtained from the 15En%- and 30En%-protein diets. In the 15En%- and 30En%-protein conditions, a higher protein intake from the soy-containing diets than from the whey with α-lactalbumin or beef containing diets was needed to meet the minimal IAA requirements.ConclusionProtein intake did not compensate for an insufficient indispensable amino acid intake with a low-protein diet for 12 days.Trial registrationThese trials were registered at clinicaltrials.gov as NCT01320189 and NCT01646749.
Highlights
Protein quality evaluation aims to determine the capacity of food sources and diets to meet protein and indispensable amino acid (IAA) requirements
This study determined whether nitrogen balance was affected and whether dietary IAA were adequately obtained from the ad libitum consumption of diets at three levels of protein from different primary sources for 12 days
Biomarker of protein intake and nitrogen balance There was a dose-dependent increase in nitrogen excretion with increasing dietary protein content, irrespective of the protein sources (P = 0.001, Table 4)
Summary
Protein quality evaluation aims to determine the capacity of food sources and diets to meet protein and indispensable amino acid (IAA) requirements. This study determined whether nitrogen balance was affected and whether dietary IAA were adequately obtained from the ad libitum consumption of diets at three levels of protein from different primary sources for 12 days. Due to a large inter-individual variability, even during energy balance and after metabolic adaptation, nitrogen balance studies are not sufficiently accurate to determine whether dietary protein intake meets IAA requirements [1,3,7]. In the context of protein-diets, the digestible IAA score (DIAAS) enables the determination whether dietary protein intake is sufficient for the metabolic needs for the individual IAA. The DIAAS permits the definition of protein quality by determination of the extent to which dietary IAA are provided in proportion to the requirements [1]
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have