Effect of increasing plant protein intake on protein quality and nutrient intake of US adults

Abstract

Three cycles of NHANES (2013–2018) were used to assess protein intake, protein quality (protein digestibility-corrected amino acid score; PDCAAS), protein cost, and nutrient intakes across quartiles of plant protein intake (Q1: <28.2%; Q2: 28.2% to <32.1%; Q3: 32.1 to <36.2%; Q4: ≥36.2%) over a 24 h period (≥19 years, n = 14 888). Grains represented the primary source of plant protein across quartiles and increased from 5.01% (Q1) to 13.5% (Q4). Across all the USDA’s Food and Nutrient Database for Dietary Studies (FNDDS) food groups, grains were the most economical source of protein (24.3–26 g protein/$1). Legumes were the most economical plant-based protein (28–37.7 g protein/$1) within the “Protein Foods” FNDDS group. Absolute protein intake (96.6 g/day) and PDCAAS (0.91) of diets were progressively lower from Q1 to 72.0 g/day and 0.8 in Q4, respectively. Modelling the replacement of 50% of amino acids from grains in the diet with amino acids from legumes increased the PDCAAS by 10% in Q4. Intake levels of fibre, folate, iron, and zinc, were higher in Q2–Q4 compared to Q1 but had lower intakes of vitamins B12 and D. Amino acid complementation is required to effectively integrate higher levels plant protein into US diets.