Diet Quality and Food Intakes Among US Adults by Level of Animal Protein Intake, What We Eat in America, NHANES 2015-2018

Background Dietary recommendations encourage consuming protein from a variety of plant and animal sources. Evaluating the diet of U.S. adults by level of animal protein (AP) intake can inform dietary assessment and nutrition education. Objective The objective of this cross-sectional study was to estimate percentage of total protein intake from animal sources by U.S. adults to compare diet quality, and intake from USDA Food Patterns (FP) groups by quintiles of AP. Methods One day dietary intake data from adults 20 + years (N = 9,566) in What We Eat in America (WWEIA), NHANES 2015-2018 were used. Proportions of total protein intake from animal and plant sources and the USDA FP groups were estimated from the ingredients in the Food and Nutrient Database for Dietary Studies 2015-2018, then applied to the dietary intakes. The 2015 Healthy Eating Index (HEI) was used as an indicator of diet quality. The USDA FP groups were used to describe contribution of animal and plant foods to total protein intake. Data were analyzed by quintile (Q) of AP protein intake; comparisons were made using pairwise t-tests with adjustments for covariates using survey sample weights. Results were considered significant at P Results Total mean protein intakes ranged from 62 (Q1)-104 grams (Q5) (All comparisons P < 0.001). Total HEI score (possible 100) of Q1 was slightly higher (54.2) (P < 0.001) compared to Q1-Q4 (range: 48.0-50.3), which did not differ significantly from each other. Contributions of plant FP components to total protein intake of Q1 to Q5, respectively were 15% to 1% from nuts/seeds, legumes, and soy products combined; 35 to 10% from grains. Contribution of animal FP components were 19-66% from meat/poultry/seafood, 14-19% dairy, 3-5% eggs. Conclusions Intake of foods considered to be good sources of plant protein was low. Overall diet quality of all adults was suboptimal regardless of plant protein intake.