Trends in the Quality and Processing of Plant-Based Diets in U.S. Youth: A Serial Cross-Sectional Analysis of NHANES, 1999-2020.

Authors

Sydney Yearley, Lu Wang, Angie Rodday, Kofi Essel, Dariush Mozaffarian

Published in

The American journal of clinical nutrition. Pages 101534. Sep 22, 2026. Epub Sep 22, 2026.

Abstract

Although U.S. youth generally underconsume healthy and overconsume unhealthy plant-based foods, national patterns of plant-based diet quality and relationships with ultra-processed food (UPF) intake are not well established.
The aim of this study was to examine temporal trends in plant-based diet quality among U.S. youth, associations with UPF intake, and differences across sociodemographic groups.
We conducted a serial cross-sectional analysis of 24-hour dietary recalls from 32,456 participants 2-19 years in the National Health and Nutrition Examination Survey (NHANES), 1999-2000 through 2017-2020. Plant-based diet quality was evaluated using the overall (oPDI), healthy (hPDI), and unhealthy (uPDI) Plant-Based Diet Indices. UPF intake was estimated as the percentage of total energy from Nova 4 foods. Survey-weighted regression analyses assessed temporal trends, relationships between PDIs and UPF, and differences by sociodemographic groups.
Overall plant-based dietary intake increased over time (46.3 to 48.0 points), accompanied by increases in healthy plant-based dietary intake (46.7 to 49.4 points) and decreases in unhealthy plant-based dietary intake (51.8 to 47.8 points) (all p-trend <0.001). Improvements were not uniform across sociodemographic groups. Overall plant-based dietary intake was higher among youth from households with higher-income, education, and food security. Healthy plant-based dietary intake was highest among females and youth from households with higher income, education, and food security. Conversely, non-Hispanic Black youth had lower healthy and higher unhealthy plant-based dietary intake, with unhealthy intake also higher among older youth and males. Healthy plant-based dietary intake was associated with lower UPF intake and unhealthy intake with higher UPF intake, with both associations strengthening over time.
Plant-based diet quality scores modestly improved among youth, but sociodemographic differences persisted. Healthy and unhealthy plant-based dietary patterns were strongly associated with UPF intake, underscoring the importance of considering diet quality, food processing, and structural determinants of diets and health.

PMID:
42772452
Bibliographic data and abstract were imported from PubMed on 23 Sep 2026.

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