Trends in Diet Quality Among US Adults From 1999 to 2020 by Race, Ethnicity, and Socioeconomic Disadvantage

Background: Few data have assessed trends in diet quality among U.S. adults. Objective: To evaluate trends in diet quality by race, ethnicity, and socioeconomic disadvantage. Design: Repeated cross-sectional study. Setting: United States. Participants: Noninstitutionalized adults aged 20 years or older who responded to the 1999-2020 National Health and Nutrition Examination Survey (NHANES). Measurements: The proportion of participants meeting the targets of the validated American Heart Association (AHA) 2020 continuous diet score (based on higher intake of fruits, vegetables, whole grains, fish and shellfish, and nuts, seeds, and legumes and lower intake of sugar-sweetened beverages, processed meat, saturated fat, and sodium) and the Healthy Eating Index (HEI)-2015, and energy-adjusted consumption of their components and other individual food groups and nutrients. Poor diet was defined as less than 40% adherence to the AHA score, intermediate as 40% to 79.9% adherence, and ideal as at least 80% adherence. Results: A total of 51 703 adults were included. From 1999 to 2020, the proportion of U.S. adults with poor diet quality decreased from 48.8% to 37.4% (difference, -11.4 percentage points [95% CI, -16.8 to -5.96 percentage points]), the proportion with intermediate quality increased from 50.6% to 61.1% (difference, 10.5 percentage points [CI, 5.20 to 16.1 percentage points]), and the proportion with ideal quality increased from 0.66% to 1.58% (difference, 0.93 percentage points [CI, 0.35 to 1.51 percentage points]) (P for trend < 0.001 for each). Persistent or worsening disparities in diet quality were observed by age, sex, race and ethnicity, education, income, food security, Supplemental Nutrition Assistance Program participation, and health insurance coverage. For example, the proportion of adults with poor diet quality decreased from 47.9% to 33.0% among those with food security (P for trend < 0.001) but did not change (51.3% to 48.2%) among those experiencing food insecurity (P for trend = 0.140) (P for interaction = 0.001). Findings were similar for HEI-2015. Limitations: Self-reported diet; cross-sectional study design. Conclusion: Diet quality among U.S. adults improved modestly between 1999 and 2020, but the proportion with poor diet quality remains high, and dietary disparities persist or are worsening.