Trends in dietary carbohydrate, protein, and fat intake and diet quality among US adults, 1999-2016

Authors: SHAN, ZHILEI - Huazhong University Of Science And Technology; REHM, COLIN - Albert Einstein College Of Medicine; ROGERS, GAIL - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; RUAN, MENGYUAN - Tufts University; WANG, DONG - Harvard University; HU, FRANK - Harvard University; MOZAFFARIAN, DARIUSH - Tufts University; ZHANG, FANG FANG - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; BHUPATHIRAJU, SHILPA - Harvard University

Submitted to: Journal of the American Medical Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2019
Publication Date: 9/24/2019
Citation: Shan, Z., Rehm, C.D., Rogers, G., Ruan, M., Wang, D.D., Hu, F.B., Mozaffarian, D., Zhang, F., Bhupathiraju, S.N. 2019. Trends in dietary carbohydrate, protein, and fat intake and diet quality among US adults, 1999-2016. Journal of the American Medical Association. 322(12):1178-1187. https://doi.org/10.1001/jama.2019.13771.
DOI: https://doi.org/10.1001/jama.2019.13771

Interpretive Summary: Understanding trends in dietary intake and diet quality can help policymakers take steps to promote better health in the US. Using data from NHANES, a nationally representative sample, we looked at carbohydrate, fat, and protein intake among US adults over a 17 year period, from 1999-2016. Our results showed that positive changes over the 17 year period, including decreased intake of added sugar and increased intake of polyunsaturated fats, plant protein, and high quality carbohydrates such as whole grains. Despite these gains, however, high intake of low-quality carbohydrates and saturated fat remains a problem.

Technical Abstract: IMPORTANCE: Changes in the economy, nutrition policies, and food processing methods can affect dietary macronutrient intake and diet quality. It is essential to evaluate trends in dietary intake, food sources, and diet quality to inform policy makers. OBJECTIVE: To investigate trends in dietary macronutrient intake, food sources, and diet quality among US adults. DESIGN, SETTING, AND PARTICIPANTS: Serial cross-sectional analysis of the US nationally representative 24-hour dietary recall data from 9 National Health and Nutrition Examination Survey cycles (1999-2016) among adults aged 20 years or older. EXPOSURE: Survey cycle. MAIN OUTCOMES AND MEASURES: Dietary intake of macronutrients and their subtypes, food sources, and the Healthy Eating Index 2015 (range, 0-100; higher scores indicate better diet quality; a minimal clinically important difference has not been defined). RESULTS: There were 43 996 respondents (weighted mean age, 46.9 years; 51.9% women). From 1999 to 2016, the estimated energy from total carbohydrates declined from 52.5% to 50.5% (difference, -2.02%; 95%CI, -2.41% to -1.63%), whereas that of total protein and total fat increased from 15.5%to 16.4% (difference, 0.82%; 95%CI, 0.67% - 0.97%) and from 32.0% to 33.2% (difference, 1.20%; 95% CI, 0.84%-1.55%), respectively (all P < .001 for trend). Estimated energy from low-quality carbohydrates decreased by 3.25% (95% CI, 2.74%-3.75%; P < .001 for trend) from 45.1% to 41.8%. Increases were observed in estimated energy from high-quality carbohydrates (by 1.23% [95% CI, 0.84%-1.61%] from 7.42%to 8.65%), plant protein (by 0.38% [95% CI, 0.28%-0.49%] from 5.38% to 5.76%), saturated fatty acids (by 0.36% [95% CI, 0.20%-0.51%] from 11.5% to 11.9%), and polyunsaturated fatty acids (by 0.65% [95% CI, 0.56%-0.74%] from 7.58% to 8.23%) (all P < .001 for trend). The estimated overall Healthy Eating Index 2015 increased from 55.7 to 57.7 (difference, 2.01; 95%CI, 0.86-3.16; P < .001 for trend). Trends in high- and low-quality carbohydrates primarily reflected higher estimated energy from whole grains (0.65%) and reduced estimated energy from added sugars (-2.00%), respectively. Trends in plant protein were predominantly due to higher estimated intake of whole grains (0.12%) and nuts (0.09%). CONCLUSIONS AND RELEVANCE: From 1999 to 2016, US adults experienced a significant decrease in percentage of energy intake from low-quality carbohydrates and significant increases in percentage of energy intake from high-quality carbohydrates, plant protein, and polyunsaturated fat. Despite improvements in macronutrient composition and diet quality, continued high intake of low-quality carbohydrates and saturated fat remained.