American diets have gotten a little healthier, but still fall short of federal government recommendations for healthy eating, finds an analysis of nationally representative interview data from 1999 to 2016.
The research, published in the Journal of the American Medical Association, analyzes a total of 43,996 adults’ one-day diet logs collected over the study period.
The analysis focuses on the macronutrients the participants reported consuming (i.e., protein, carbohydrates and fats) and the food sources from which they were derived. These food sources are further categorized — for example, carbohydrates derived from whole grains would be further classified as high-quality, whereas carbohydrates derived from foods containing added sugar would be considered low-quality.
This approach is key because, health-wise, not all carbs (or fats, or proteins) are created equal.
To see how Americans’ diets fare, researchers compared the data with the most recent dietary guidelines issued by the U.S. Department of Health and Human Services and U.S. Department of Agriculture.
“Looking at these trends gives us a big overview as to how diets are changing, and this can provide information to policymakers, or to other health agencies, regarding which groups to target, where we are falling short and where we need to improve,” says Shilpa Bhupathiraju, senior author of the paper and a research scientist in the department of nutrition at the Harvard T.H. Chan School of Public Health.
Diets were also examined according to demographic factors including age, socioeconomic status and education level. Income was determined by the ratio of family income to poverty level. Education was categorized as either less than a high school education, high school graduate or GED, or some college.
The data is limited in that it captures only a day of eating. Dietary intake can vary drastically from day to day (as anyone who’s had a bad day and treated themselves to French fries well knows). However, the authors used a pre-established method that draws on typical estimates of 24-hour dietary intake in order to reduce potential outliers in daily consumption.
The key findings were:
- On the whole, diets of adults in the U.S. have improved slightly. The Healthy Eating Index 2015, used to measure dietary quality on a scale of 0 to 100, increased from 55.7 to 57.7 between 1999 and 2016.
- Over time, respondents reported lower total carbohydrate intake. Between 1999 and 2016, the percentage of calories derived from carbohydrates declined from 52.5% to 50.5%. Further, the composition of carbohydrates consumed improved. Respondents reported a 3.25% decrease in calories from low-quality carbohydrates consumed and a 1.23% increase in calories from high-quality carbohydrates.
- Respondents reported small increases in their consumption of plant protein and polyunsaturated fat, a healthy fat found in sources like fish, nuts and seeds that can help reduce cholesterol levels.
- Adults between the ages of 20 and 34 and adults with higher education or income levels reported greater improvements in diet — reductions in low-quality carbohydrate consumption and increases in polyunsaturated fat intake, for example — than adults over age 65 and adults with lower levels of education or income.
“These analyses do show these subgroups to target,” Bhupathiraju says. “People who really need help are older people and those with lower income and education.”
She suggests that better health education and greater access to healthy foods might explain why people who are younger, wealthier and better educated tend to eat healthier. She notes that policy interventions might incorporate these strategies.
As an example of how health education has improved in recent years, Bhupathiraju pointed to the shifts in the framing of federal nutrition guidelines.
“In the past we focused on single nutrients. But people consume foods,” Bhupathiraju says. “They [nutrition experts] have shifted away from looking at individual nutrients to foods and dietary patterns… the focus of all these eating patterns is the same, it’s high-quality carbs, proteins — mostly from plants, and if you do include animal protein, mostly from seafood and poultry — an abundance of fruits and vegetables and minimally processed foods.” Continuing to promote health education efforts might further enhance the quality of diets in the U.S., she says.
“I think the focus moving away from single nutrients to eating patterns, it’s more relatable to the general public,” she adds. “When people say, ‘Eat so many grams of vegetables,’ that’s not clearly understandable. Even to a person in nutrition science, it’s hard to understand.”
Despite improvements in overall diet quality and health education, Bhupathiraju notes that eating habits in the U.S. still need work.
“Diets have been improving, but still 42% of energy comes from refined grains,” she says. “Saturated fatty acids — those remain above the recommended amount. Added sugar has decreased, but it’s still about the recommended upper limit of 10%. So, we’re making a small improvements, but we still have a really, really long way to go to meet the dietary recommendations and to be where we want to be in terms of healthy eating.”
Citation: Shan, Zhilei; et al. “Trends in Dietary Carbohydrate, Protein, and Fat Intake and Diet Quality Among US Adults, 1999-2016,” Journal of the American Medical Association, September 2019. doi: 10.1001/jama.2019.13771.