Diet Quality Has Been Declining in the US Since Early 2000s, Study Finds

Chenkai Wu, PhD, MPH

As the obesity epidemic has grown, the decline in diet quality among citizens in the US has become a major point of discussion. Thanks to a recent study from investigators at the Global Health Research Center of Duke Kunshan University, clinicians now have an overview of the declining diet quality among older adults in the US from 2001-2018.

A serial cross-sectional analysis of data from 9 National Health and Nutrition Examination Survey (NHANES) cycles, results of the study provide insight into the declining diet quality among weighted population according to diet scores based on the American Heart Association (AHA) 2020 Strategic Impact Goals for diet and the Healthy Eating Index (HEI)–2015 score.

“The most notable finding was the overall trend of deterioration in diet quality among older adults. All 3 composite diet scores—the primary AHA diet score, the secondary AHA diet score, and the HEI-2015 score—showed a modest decrease between 2001 and 2018. The proportion of older US adults with poor diet quality increased by 10%, and the proportion with an ideal diet quality remained consistently low,” wrote investigators.

Led by Chenkai Wu, PhD, MPH, and colleagues from the Duke Kunshan University in Jiangsu, China, the current study was designed with an interest in describing contemporary trends in diet quality and nutrition among older adults in the US based on multiple factors, including age, sex, race and ethnicity, marital status, education level, and income. With this in mind, investigators conducted the serial cross-sectional study using 24-hour dietary recall data from 9 NHANES cycles beginning with the 2001-2002 cycle and ending with the 2017-2018 cycle.

The primary outcomes of interest for the study were survey-weighted, energy-adjusted mean diet scores and proportions of older US adults with poor, intermediate, or ideal diet scores based on the AHA 2020 Strategic Impact Goals for diet. Secondary outcomes of interest for the study included the AHA secondary score and the HEI-2015 score.

Briefly, the AHA 2020 Strategic Impact Goals for diet provided criteria for establishing AHA primary and secondary diet scores. The primary score incorporated data from 5 components, including fruits and vegetables, fish and shellfish, sodium, and more, and scores could range from 0 to 50, with 0 being the lowest possible score. Secondary scores ranged from 0 to 80 and included 3 additional components, which were nuts, seeds, and legumes, processed meat, and saturated fat.

A cohort of 10,837 adults aged 65 years or older and completed the 24-hour dietary recall were identified for inclusion in the investigators’ analyses. This cohort was 50.0% women, 58.5% were White, and the mean age was 73.9 (SD, 0.1) years. From the first survey cycle to the last, the proportion of patients aged 65-69 years increased from 30.8% to 35.4% and the proportion of adults aged 80 years or older decreased from 23.3% to 19.3%.

Results of the investigators’ analyses indicated overall dietary quality deteriorated during the study period. Specifically, the mean primary AHA score decreased from 19.84 (95% CI, 19.40 to 20.29) to 18.28 (95% CI, 17.84 to 18.73; a decrease of 7.9%; P <.001 for trend). The mean secondary AHA score decreased from 34.75 (95% CI, 34.11 to 35.39) to 31.83 (95% CI, 31.17 to 32.48; a decrease of 8.4%; P <.001 for trend), and mean HEI-2015 score decreased from 47.82 (95% CI, 47.11 to 48.52) to 45.25 (95% CI, 44.53 to 45.98; a decrease of 5.4%; P <.001 for trend).

Highlighted trends from the individual components of diet scores are listed below:

• Mean consumption of total fruits and vegetables significantly decreased from 3.90 (95% CI, 3.62 to 4.19) to 2.49 (95% CI, 2.13 to 2.86) servings per day (difference, −36.1% [95% CI, −45.5% to −26.8%]).
• Mean consumption of nuts, seeds, and legumes decreased from 0.37 (95% CI, 0.29 to 0.46) to 0.31 (95% CI, 0.25 to 0.38) servings per day (difference, −16.5% [95% CI, −33.9% to 0.9%]).
• Mean consumption of processed meat increased from 0.40 (95% CI, 0.35 to 0.45) to 0.42 (95% CI, 0.33 to 0.51) servings per day (difference, 5.2% [95% CI, −16.7% to 27.1%]).
• Mean consumption of saturated fat increased from 0.36 (95% CI, 0.35 to 0.37) to 0.40 (95% CI, 0.39 to 0.41) servings per day (difference, 11.6% [95% CI, 8.8% to 14.3%]).

*All trends above are from 2001-2002 to 2017-2018.

Using the primary AHA score, results suggested the proportion of US older adults with a poor diet quality significantly increased from 50.9% to 60.9% from 2001-2002 to 2017-2018. During the same time period, the proportion with an intermediate diet quality significantly decreased from 48.6% to 38.7% and the proportion with ideal diet quality remained consistently low, at a rate of 0.4% in both 2001-2002 and 2017-2018.

“Despite increases in educational and income levels, overall dietary quality has decreased from 2001 to 2018 based on the AHA and HEI scores among older adults in the US. Older adults have become the fastest-growing segment of the US population; specific attention should be focused on their diets and on diet-related policy to improve their health,” investigators wrote.

This study, “Trends in Diet Quality Among Older US Adults From 2001 to 2018,” was published in JAMA Network Open.