How nutritionists evaluate what Americans should eat

Every five years since 1980, the federal government has released dietary guidelines, providing advice to Americans on what to eat.

 These guidelines—which have served as the basis for visual aids like the ubiquitous food pyramid of the 1990s and MyPlate graphic of 2011—are considered the “cornerstone” of our country’s nutrition policy and education.

Before the guidelines are revised, the US Department of Agriculture and Department of Health and Human Services convene an independent advisory committee of nutrition experts, who are tasked with digging into the latest research and using data to answer specific, unanswered questions about diet and nutrition. The committee’s findings, along with comments from the public, inform the federal government's updated guidelines. 

Andrea Deierlein, director of public health nutrition at the NYU School of Global Public Health, was one of the 20 members of the 2025 Dietary Guidelines Advisory Committee. Her research in nutritional epidemiology focuses on maternal and child health, including nutrition during and after pregnancy, exposure to environmental chemicals, and disability-related disparities in nutrition and reproductive health.

NYU News spoke with Deierlein about some of the key takeaways from her work on the advisory committee.

Nutrition is hard to study—but the committee’s report is based on the most rigorous science.

Studying what we eat and its impact on our bodies is no small task. Some research focuses on single foods or nutrients, missing the big picture of how people actually eat. Other studies have people change their diets for a few weeks and measure short-term changes in outcomes such as glucose or cholesterol, leaving researchers wondering whether these changes are meaningful for long-term health. 

“Diet is a really complicated exposure to study. The way to study diet is how we eat collectively, in patterns,” said Deierlein. “Ideally, you need large datasets that follow people for a long period of time. Many chronic diseases have long latency periods, and there is evidence that dietary exposures early in life have long-lasting impacts.” 

Deierlein and her colleagues on the advisory committee spent nearly two years wading through decades of nutrition research to find the highest-quality studies and synthesize what they tell us about our diets. Their analyses were limited to randomized controlled trials (often considered the “gold standard” for human studies), prospective cohort studies that followed people over time, or studies that tested interventions like a specific diet. The committee excluded cross-sectional studies, which only provide a snapshot of health outcomes at one point in time.

As a result, the committee’s recommendations are grounded in rigorous research—but its work also highlights the need for more high-quality nutrition studies that follow people’s dietary patterns over time.

“We think everything has been studied, but it hasn’t,” said Deierlein.

How kids are fed may be as important as what they are fed.

The current dietary guidelines take a “lifespan approach” to guide Americans on what to eat at different stages of life, from birth through older age. The latest research shows that kids in early childhood tend to have healthier diets than older children and teens, while older adults generally have better diet quality than younger adults.

Given her expertise on nutrition during pregnancy and childhood, much of Deierlein’s work on the advisory committee focused on these phases in life. When examining the research on younger children, Deierlein and her colleagues looked at the importance of how kids are fed and its role in shaping their diets. When caregivers repeatedly expose young kids to fruits and vegetables by, for instance, having fruit in the home, serving vegetables at snacks, or showing kids that eating vegetables can be delicious, this increases children’s intake of fruits and vegetables. 

Plants can provide protein.

The advisory committee found that most people in the US could be eating healthier diets, with more fruits and vegetables and less meat and refined grains.

One new recommendation from the committee’s report: eating more plant-based proteins and less red and processed meats. In fact, the committee suggests reclassifying beans, peas, and lentils as proteins instead of vegetables, as research and modeling show that plant-based proteins can generally meet protein goals.

There’s more than one “American” diet. 

Did you grow up eating oatmeal or grits at breakfast? Do you usually serve rice or potatoes at dinner? Where we live, our families, and our backgrounds often play a role in what foods we eat—but that doesn’t mean that nutrition research and federal food programs have historically taken this into account. 

“Food assistance programs may not cover items that are culturally important to different communities,” said Deierlein.

The committee’s work on the next food guidelines paid attention to “cultural foodways,” noted Deierlein—recognizing the different cultural, regional, social, and religious needs of people living in the United States. As the country’s population has grown more diverse over the past decade, the committee’s focus on health equity was designed to help HHS and USDA make the next dietary guidelines relevant to and adoptable by people of diverse backgrounds. This framework led to the committee proposing the “Eat Healthy Your Way” dietary pattern, which is designed to be flexible and inclusive while still meeting nutritional needs.

As part of this work, the committee used computer modeling to simulate diets in order to quickly test whether different combinations of foods can provide adequate nutrition. To pilot this novel approach, committee members—including experts in American Indian and Alaska Native culture and nutrition—input foods traditionally eaten in Indigenous diets. The diet simulations revealed that nutrition requirements can be met by consuming a wide variety of foods, including those eaten in American Indian and Alaska Native communities. 

We need more research on ultra-processed foods.

Ultra-processed foods—industrial formulations that include additives and preservatives, and tend to be higher in sugar, saturated fat, and salt—have come under scrutiny in recent years.

The advisory committee, tasked with reviewing the science on ultra-processed foods and weight gain, found a link between diets high in these foods and obesity in children, teens, and adults. However, only a limited number of studies on the topic met the committee’s high standards, and research on the effects of these foods during other phases of life—including pregnancy and early childhood—was even more limited. 

One challenge limiting research on ultra-processed foods: there’s no single set of criteria for it, which makes it hard to measure and compare across studies. The advisory committee noted that a more rigorous definition of ultra-processed foods and additional research on diets containing them could shift future conclusions and should continue to be studied.

Nutrition experts tend to agree that minimizing our consumption of ultra-processed foods is important for our health, but ultra-processed foods may not all be equally unhealthy (for instance, a fruit-flavored yogurt has more nutrients than a bag of chips, even though both meet some definitions of “ultra-processed”). This is something that Deierlein is looking into in her own research with collaborators at Stevens Institute of Technology, harnessing the power of machine learning algorithms to break ultra-processed foods into smaller food groups to study further.

“Although the dietary guidelines can’t do much to change the US food environment, we can help people make better decisions about food and hopefully improve food programs and policy,” said Deierlein.

The scientific report of the 2025 Dietary Guidelines Advisory Committee was released in December, and the USDA and HHS will release the 2025-2030 Dietary Guidelines for Americans by the end of the year.