Abstract
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 (Quartile1: 0-24.9%; Quartile2: 25%-49.9%; Quartile3: 50-74.9%; Quartile4: 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 quartiles1-3, but decreased (p < 0.0001) to 0.71 ± 0.018 in quartile4 vs. quartile2 (0.96 ± 0.004). Corrected protein intakes in quartile2 (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 quartile4 (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.
Highlights
Amino acids are required for growth, maintenance, and metabolism
The mean proportion of individuals allocated to quartiles of increasing proportions of plant protein was related to income levels
Plant protein foods are increasingly emphasized as components of healthy and environmentally sustainable dietary patterns
Summary
Amino acids are indispensable when they cannot be endogenously synthesized or synthesized at rates commensurate with metabolic needs. Their consumption from dietary protein is required. The ability for dietary protein to meet the indispensable amino acid (IAA) requirements for growth, maintenance, and/or metabolic work for humans and animals is reflected in the term “protein quality” (PQ). Proteins derived from animals typically have a higher PQ than proteins from plant sources This is due to the fact that animal proteins typically present with higher levels of IAAs per gram protein that align with human requirements, and digestibility coefficients that are >90% (Tome 2013). Plant protein foods can contain other constituents, such as fibre and antinutritional factors, that may affect IAA digestibility (Gilani et al 2005)
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