Dietary habits improved among Americans

1. Between 1999 and 2012 there have been several improvements in self-reported dietary habits, as quantified by American Heart Association diet scores. These improvements were attributed to increase consumption of whole grains, nuts or seeds, and decreased consumption of sugar sweetened beverages.

2. There are potentially increasing disparities in diet quality among US citizens based on their race/ethnicity, education, and income level.

Evidence Rating Level: 2 (Good)

Study Rundown: Poor dietary intake is a risk factor for many diseases including obesity, diabetes, cardiovascular illness and some cancers. In the past, studies regarding US dietary trends have been limited to only a few dietary factors or nutrients. This study sought instead to quantify trends in summary measures of diet for many food groups and nutrients and assessed a large, nationally representative sample of 24-hour dietary intake. This survey information was translated to the American Heart Association (AHA) 2020 continuous diet score, which served as the primary summary indicator. The study found that there was an 11.6% improvement in AHA primary diet score and a 9.7% improvement in AHA secondary diet score. These improvements were attributed to increased consumption of whole grains, nuts or seeds, and to a decreased consumption of sugar-sweetened beverages. Further, the percentage of US adults with poor diets declined substantially. In addition, the study sought to identify dietary disparities between US adults as pertaining to their age, sex, race/ethnicity, education and income.

Disparities in diet quality were seen primarily in race/ethnicity, education and income level, thus indicating the need for intervention in this domain. This study was limited by its use of self-reported data, which is inevitably subject to systematic and random error. In addition, the use of a summary measure of diet has yet to be validated against clinical end points. However, its results point towards an overall improving diet among Americans over the past 15 years.

Click to read the study in JAMA

Relevant Reading: The state of US health, 1990-2010

In-Depth [cross-sectional study]: This study utilized data contained in sequential cycles of the National Health and Nutrition Examination Survey (NHANES), between 1999 and 2012. The NHANES database contains results from 24-hour dietary recall surveys, and in the years included, contains information on the diets of 33 932 patients over the age of 20. The main goal of this study was to characterize how the average American diet has changed over time, and in doing so it evaluates how the year of participation and the socioeconomic status of respondents affects diet. The main outcome measured was the AHA 2020 continuous diet score, which is calculated from the total consumption of fruits and vegetables, fish and shellfish, sodium, sugar-sweetened beverages, and whole grains. A higher score indicates a healthier diet.

The study found that the AHA primary score and secondary score (which adds in other food groups) improved over time by 11.6% and 9.7%, respectively (p < 0.01 for trend). This improvement in diet was lead predominantly by increased consumption of whole grains (increase 0.43 servings/day from 1999 to 2012; 95%CI 0.34–0.53) and nuts or seeds (increase 0.25 servings/day; 95%CI 0.18–0.34), as well as by a decrease in sugar-sweetened beverages (decrease 0.49 servings/day; 95%CI 0.28–0.70). There was no significant change over time in the consumption of fruits and vegetables, processed meats, saturated fats, or sodium. Overall, the percentage of respondents with a poor diet (<40% adherence to AHA goals) decreased from 55.9% to 45.6%. This lower rate was due largely to improved diets among non-Hispanic white respondents, and there was no apparent improvement in diet among Hispanic and non-Hispanic black Americans.

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