The effect of increasing intakes of plant protein on the protein quality of Canadian diets.

The 2015 Canadian Community Health Survey was used to investigate the protein content and protein quality of the diets consumed by adults (≥19 years) when plant protein is increased. Individuals (n = 6498) were allocated to quartiles of increasing proportions of protein from plant foods (Quartile 1: 0-24.9%; Quartile 2: 25%-49.9%; Quartile 3: 50-74.9%; Quartile 4: 75-100%). The Protein Digestibility Corrected Amino Acid Score (PDCAAS) of diets were estimated using indispensable amino acid concentrations of foods and an assumed digestibility coefficient of 0.8. Corrected protein intakes were determined by aggregating foods consumed over 24 hours and as the sum of corrected protein consumed at eating events within six 4-hour time intervals. Most individuals (51%) consumed 25-49.9% of protein from plant foods. Cereal-based foods represented the majority of plant protein consumed. PDCAAS of diets remained ≥0.87 for quartiles 1-3, but decreased (p < 0.0001) to 0.71 ± 0.018 in quartile 4 vs. quartile 2 (0.96 ± 0.004). Corrected protein intakes in quartile 2 (80.66 ± 1.21 g/day; 1.07 ± 0.03 g protein/kg body weight) decreased to 37.13 ± 1.88 g/day (0.54 ± 0.03 g/kg body weight) in quartile 4 (p < 0.0001). Aggregated daily corrected protein intake strongly correlated (r = 0.99; p < 0.001) with the sum of corrected protein consumed within time intervals. Intra-time interval analysis revealed that the relative proportions of animal and plant proteins changed at eating events over 24 hours and did not reflect the allocation to quartiles based on the daily proportion of plant protein consumption. Various tools should be explored and developed to assist Canadians in effectively incorporating plant protein foods into dietary patterns. Novelty: Corrected protein intakes decreased as plant protein consumption increased. PDCAAS was ≥0.87 for diets with ≤74.9% plant protein.