American diets have improved in the last several decades, with declines in consumption of low-quality carbohydrates and increases in plant protein and healthy fats, based on data from a nationally representative sample of 43,996 adults.
Changes in the economy, food policies, and food processing can affect diet over time, but trends in consumption of macronutrients in the U.S. have not been well studied, wrote Zhilei Shan, MD, of Harvard T.H. Chan School of Public Health, Boston, and colleagues.
In a study published in JAMA, the researchers reviewed data from nine consecutive cycles of the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2016 to determine trends in macronutrient intake. The study population included adults aged 20 years and older who could provide at least 1 valid dietary recall questionnaire. The average age was 47 years, and 52% were women.
Overall, total carbohydrate consumption decreased from 52.5% to 50.5%, the estimated energy from high-quality carbohydrates increased from 7.42% to 8.65%, and the estimated energy from low-quality carbohydrates decreased from 45.1% to 41.8%. Total protein consumption increased from 15.5% to 16.4%, and plant protein consumption increased from 5.38% to 5.76%. Total fat consumption increased from 32.0% to 33.2%, including a 0.36% increase in saturated fatty acids from 11.5% to 11.9% and a 0.65% increase in polyunsaturated fatty acids from 7.58% to 8.23%.
Although the changes in total carbohydrates, total protein, and total fat were significant, 42% of energy intake came from low-quality carbohydrates and 10% came from saturated fat, the researchers noted. Also, the overall diet quality as measured by the Healthy Eating Index 2015 (HEI-2015) improved from 55.7 in 1999 to 57.7 in 2016. The HEI-2015 measures how diet data adheres to recommendations in the 2015-2020 Dietary Guidelines for Americans on a scale of 0-100.
“Improvements in intakes of whole grains and plant protein are encouraging, but how much do popular foods such as pizza, fast food sandwiches and burgers, and foods categorized as ‘snacks’ and ‘desserts’ contribute to the U.S. eating pattern?” wrote Linda Van Horn, PhD, RDN, and Marilyn C. Cornelis, PhD, of Northwestern University, Chicago, in an editorial accompanying the study. They cited a closer look at the NHANES data in the USDA’s “What We Eat in America” report and noted the differences in ethnicity with regard to macronutrient consumption.
“Non-Hispanic whites consume more alcohol, pizza, and fast food sandwiches (24% of total energy), while non-Hispanic blacks consume more salty snacks and sweet desserts (17% of total energy), and Hispanics consume more sugar-sweetened beverages (8% of total energy) and the least alcohol compared with the other racial/ethnic groups,” they said. “Public health efforts to educate, inform, and incent better adherence to the recommended nutrient-dense food groups are clearly needed,” they emphasized.
The study findings were limited by several factors, including the use of self-reports and changes in dietary assessments over time, the researchers noted. However, the results are strengthened by the large sample size and suggest improvements in the overall American diet, but also highlight the need for continuing public education and intervention, they said.
The study was supported by the National Institutes of Health and the Young Scientists Fund of the National Natural Science Foundation of China. Dr. Shan had no financial conflicts to disclose. Dr. Van Horn disclosed being a member of the 2020 US Dietary Guidelines Advisory Committee.
SOURCE: Shan Z et al. JAMA. 2019. doi: 10.1001/jama.2019.13771.