Trends in Plant-Based Diets among United States Adults, 1999-March 2020

Abstract

Background: Interest in plant-based eating has increased alongside increased variety and availability of highly processed plant-based meat and dairy alternatives. The impact of the shifting commercial landscape and public interest in plant-based eating on dietary intake is unknown.

Objectives: To examine trends in the consumption and composition of plant-based diets in the United States adults.

Methods: Serial cross-sectional data from the National Health and Nutrition Examination Survey were used to assess trends in the proportion of United States adults aged ≥20 y consuming a plant-based diet (defined as ≥50% total protein from plants on a 24-h dietary recall) from 1999-2000 to 2017-March 2020 (n = 51,698). Trends in processing level (percentage energy intake from ultraprocessed foods) and diet quality [Healthy Eating Index (HEI)-2020 scores] were assessed in the subset of adults consuming plant-based diets (n = 8327).

Results: The proportion of United States adults consuming plant-based diets increased from 14.4% (95% CI: 12.9%, 16.0%) to 17.2% (95% confidence interval [CI]: 15.5%, 19.1%; P = 0.005 for trend). In all survey cycles, ultraprocessed foods accounted for the majority of energy intake, and ultraprocessed food intake in plant-based diets did not significantly change over time [50.7% kcal (95% CI: 47.3%, 54.1%) in 1999-2000 compared with 52.7% kcal (95% CI: 49.7%, 55.6%) in 2017-March 2020; P for trend = 0.34]. The quality of plant-based diets, measured by HEI-2020 scores, improved from 52.1 (95% CI: 49.7, 54.6) to 55.8 (95% CI: 54.1, 57.5; P for trend <0.001).

Conclusions: Between 1999 and March 2020, the proportion of United States adults consuming a plant-based diet increased. Among people consuming plant-based diets, ultraprocessed foods contributed most to energy intake and there was no sustained change in intake over time. The mean diet quality was low but improved modestly.

Keywords: NHANES; NOVA; diet; plant-based; trend; ultraprocessed; vegetarian.

FIGURE 1

Trends in the estimated proportions of United States adults consuming plant-based and vegetarian diets, 1999–March 2020. Point estimates are weighted proportions of adults consuming plant-based (≥50% protein from plants; square markers connected with solid line) and vegetarian diets (circle markers connected with dashed line). Vertical lines through point estimates display 95% confidence interval. P values above each line are for the corresponding test of linear trend.

FIGURE 2

Trends in energy intake (% total kcal) from NOVA groups among United States adults who consumed plant-based diets, 1999–March 2020. Point estimates are mean percentage of total energy intake (% kcal) from ultraprocessed foods (orange circles), processed foods (green diamond), culinary processed ingredients (blue triangles), and minimally processed and unprocessed foods (navy squares). P values above each line are the corresponding test of linear trend.

FIGURE 3

Changes in energy intake (% total kcal) from ultraprocessed food subgroups among United States adults who consumed plant-based diets, 1999–March 2020. Difference compares mean intakes (as % kcal) in 1999–2000 compared with 2017–March 2020; positive values represent increased intake and negative values represent decreased intake over time.