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.
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.
- 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.
“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.”