The Average US Diet Is Improving, but Remains Suboptimal for Many

A new study of more than 50,000 people is highlighting the suboptimal quality of the typical US diet.

Led by the Food Is Medicine Institute at the Friedman School of Nutrition Science and Policy at Tufts University, the study results showed that more than 1 in 3 US adults surveyed in 2020 had poor diet quality, measured by using a validated score from the. American Heart Association, with less than 2% achieving ideal diet quality.¹

“We are facing a national nutrition crisis, with continued climbing rates of obesity and type 2 diabetes,” said Dariush Mozaffarian, MD, DrPH, Cardiologist and director of the Food is Medicine Institute.²“These diseases affect all Americans, but especially those who are socioeconomically and geographically vulnerable. We must address nutritional security and other social determinants of health including housing, transportation, fair wages, and structural racism to address the human and economic costs of poor diets.”

As the US grapples with increasing obesity and epidemics of type 2 diabetes increasing the prevalence of cardiovascular disease, the quality of the diet in the US has been cited as a key driver of this increase in risk factors. However, despite the renewed interest in population diet and nutrition, few studies offer a comprehensive assessment of trends in overall diet quality among US adults.

With this in mind, Mozaffarian and Junxiu Liu, PhD, designed the current study to address these research gaps using nationally representative data. Funded by the National Institutes of Health, the cross-sectional study leveraged data from adults aged 20 and older who participated in the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2020.¹

To be included in the study, patients had to have at least 1 valid 24-hour dietary recall in the dietary interview component of NHANES. In total, 51,703 adults who completed at least 1 valid 24-hour dietary recall were identified for inclusion. This cohort had an average age of 47.0 years and 51.9% were women. Among those who had 1 valid recall of a 24-hour diet, 72.6% gave 2 recalls.¹

Some significant trends during the study period by investigators. These included an increase in older adults (16.3% to 21.7%), a decrease in the proportion of younger patients (53.8% to 43.7%), an increase in the number of Hispanic adults (14.0% to 16.1%), and an increase in the number of Hispanic adults. an increase in the number of people who reported some or more college education (49.8% to 62.1%). In addition, investigators showed participation in SNAP more than doubled (8.62% to 16.7%), the proportion with government-sponsored health insurance increased (13.2% to 28.1%), and the proportion with health insurance decreased private (67.2% to 58.4% ).¹

The study’s primary outcome of interest was the percentage of patients who achieved the AHA 2020 validated continuous score goals. By using the AHA score, which awards higher scores based on higher intakes of fruits and vegetables, whole grains, fish and shellfish, and nuts, seeds, and legumes and lower intakes of sugar-sweetened beverages, processed meats, saturated fat , and sodium, Poor diet was defined as less than 40% adherence, intermediate as 40% to 79.9% adherence, and ideal as at least 80% adherence.¹

The study results indicate that the estimated percentage of US adults with poor diet quality decreased from 48.8% to 37.4% (difference, -11.4 percentage points; 95% CI, -16.8 to -5.96 percentage points), increased the estimated proportion with intermediate quality increased from 50.6% to 61.1% (difference, 10.5 percentage points; 95% CI, 5.20 to 16.1 percentage points), and the estimated proportion with an ideal diet increased from 0.66% to 1.58% (difference, 0.93 percentage point; 95% CI, 0.35 to 1.51 percentage point) (p for trend <.001 per head) from 1999 to 2020. When assessing outcome continuously, the results showed that the mean AHA score increased from 32.8 out of 80 to 36.7 out of 80 during the study period (difference, 3.95; 95% C, 2.28 to 5.62) (p for trend <.001).¹

When considering specific trends in nutrition, the results showed that statistically significant reductions were observed in the intake of sugar (86.2 to 63.1 grams per day), sugar-sweetened beverages (1.73 to 1.0 servings per day), fruit juice (0.44 to 0.22 servings per day ), refined grains (5.49 to 5.24 servings per day), and milk (0.90 to 0.54 servings per day) (p for trend <.001 per each).¹

Investigators pointed to numerous differences found within their research, including greater improvements in diet quality observed among younger adults compared to older adults, those with higher incomes compared to lower income, those with food security versus food insecurity, and those with private health insurance versus government health insurance (p for interaction <.05 for all).¹

“While we’ve seen modest improvements in American diets over the past two decades, those improvements are not universal, and many Americans are eating worse,” Mozaffarian said.²“Our new research shows that the nation cannot achieve nutrition and health equity until we address the barriers many Americans face in accessing and eating nutritious food.”

References:

1. ^{Liu J, Mozaffarian D. Trends in Diet Quality Among US Adults From 1999 to 2020 by Race, Ethnicity, and Socioeconomic Disadvantage. Annals of Internal Medicine. Published online June 17, 2024. doi:10.7326/M24-0190}
2. ^{Tufts University. American diets have a long way to go to achieve health Equity. News. June 17, 2024. Accessed June 17, 2024. https://www.newswise.com/articles/american-diets-have-a-long-way-to-go-to-achieve-health-equity.}