Diet trends over the past two decades in the United States

1. In this serial, cross sectional analysis over the last two decades, the adults in the United States decreased consumption of low-quality carbohydrates and increased intake of high-quality carbohydrates, plant protein, and polyunsaturated fat.

2. However, consumption of saturated fats and low-quality carbohydrates, primarily sugar, still remain above the recommended level.

Evidence Rating Level: 2 (Good)

Study Rundown: Diet is known to play an important role in overall health, yet having a poor diet was recently estimated as the leading cause of death in the United States (US). Consequently, research evaluating the trends in carbohydrate, fat, and protein intake among US adults is much needed. In this serial, cross-sectional analysis over the last two decades, US adults decreased consumption of low-quality carbohydrates in favor of high-quality carbohydrates, due to inclusion of more grains and fewer added sugars. Study participants also increased consumption of plant protein and polyunsaturated fat. An amalgamation of dietary changes reflected a small, but significant, overall improvement in US diets by the Healthy Eating Index. However, consumption of saturated fats and low-quality carbohydrates, primarily sugar, still remained above the recommended level.

Overall, this study was well-designed and reports recently compiled data summarizing dietary trends over the last two decades. However, this study was limited by self-reported dietary data, which may have underestimated calorie consumption. Also, demographic shifts, which may have contributed to these trends, could not be commented on due to the cross-sectional nature of this analysis.

Click to read the study in JAMA

Relevant Reading: The State of US Health, 1990-2016: Burden of Diseases, Injuries, and Risk Factors Among US States

In-Depth [cross-sectional study]: 43,996 adults 20 years of age and older who completed the National Health and Nutrition Examination Survey (NHANES) questionnaire at least once were included, and information on race/ethnicity was self-reported by NHANES participants via standardized questionnaires according to categories provided by the NCHS (non-Hispanic white, non-Hispanic black, Mexican American, other Hispanic, or other). A 24-hour recall questionnaire format was used to collect the data. The data collection methods varied from year to year, being in person initially, then phasing into a telephone interview, followed by administering the “multiple-pass method”. Participants with invalid diet recalls were excluded. The study reported the estimated energy from total carbohydrates decreased from 52.5% to 50.5% (difference −2.02%; CI95 −2.41% to −1.63%), whereas that of total protein and total fat increased from 15.5% to 16.4% (difference 0.82%; CI95 0.67% to 0.97%) and from 32.0% to 33.2% (difference 1.20%; CI95 0.84% to 1.55%), respectively (all p < 0.001). Holistically, US diets improved according to the Healthy Eating Index 2015, which increased from 55.7 to 57.7 (difference 2.01; CI95 0.86 to 3.16). Overall, 42%of energy intake was derived from low-quality carbohydrates and the intake of saturated fat remained above 10% of energy.

Image: PD

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