Trends in sustainable dietary patterns in United States adults, 2007-2018.

Objectives: Adopting sustainable diets is essential for improving both human and planetary health, and such diets should be evaluated from a multidimensional perspective. We characterized trends in sustainable dietary patterns, quantified by the Sustainable Diet Index for US adults (SDI-US), along with trends in diet quality, diet-related environmental impacts, food affordability, and food practices.

Methods: This study analyzed data from the National Health and Nutrition Examination Survey (2007-2018) for adults aged ≥20 years (n = 25,543). The SDI-US (range: 4-20 points), with higher scores indicating more sustainable diets, was calculated using 24-hour dietary recall data and responses to consumer and dietary behavior questionnaires. Mean total SDI-US scores, sub-indices, and 12 individual indicators were estimated for each survey cycle. Trends were assessed using orthogonal polynomial contrasts in regression models.

Results: From 2007 to 2018, total SDI-US scores showed no significant overall trend (overall mean = 13.1). Nutritional and sociocultural indicators remained relatively stable, whereas the economic indicator (food expenditures) worsened from 21.4% to 26.4% (p<0.05, linear trend) between 2007-2008 and 2017-2018. Environmental impacts initially worsened between 2007-2008 and 2013-2014 but improved through 2017-2018 (all p<0.05, quadratic trend). When stratified by age (p for interaction <0.0001), a slight decline in SDI-US was observed among adults aged ≥60 years (14.1 to 13.9, p<0.0001).

Conclusion: From 2007 to 2018, total SDI-US scores largely remained unchanged, although declines occurred among adults ≥60 years and scores remained lower among adults aged 20-39 years. Ongoing monitoring and coordinated improvements across all dimensions are needed to advance sustainable diets in all age groups.