There’s a fundamental barrier to scientific certainty in food science. People eat foods, not nutrients.
The experts charged with advising federal health officials on the 2025-2030 Dietary Guidelines for Americans had to scale a mountain of research challenges like this basic impediment, starting with the impossibility of randomly assigning people to eat only x or y for 30 to 40 years. They completed their two-day meeting on Tuesday to discuss draft recommendations they will send to the Department of Health and Human Services and the Department of Agriculture. Guidelines will be published in December.
The panel appears unlikely to recommend major changes, citing inadequate data in several areas, including limited understanding of how changing specific dietary patterns might help improve health. In Monday’s meeting the group said it would not weigh in on ultra-processed foods, citing the dearth of data or even a definition. On alcoholic beverages, it deferred to scientific reviews underway within HHS and the National Academies of Sciences, Engineering, and Medicine.
The next time around, culturally tailored dietary interventions will move to a systematic review from this iteration’s scan of the evidence, the panel promised.
Still, agreement was solid on some bedrock findings: Saturated fat is bad for us, tightly linked to heart disease. National guidelines dating to 2005 have urged limiting saturated fat, currently set at no more than 10% of total calories. Few Americans — about 1 in 5 — actually meet that goal, the researchers reminded their online audience.
Adolescents are getting more than the recommended amounts of saturated fats, for example, but it’s important to remember how.
“This isn’t that kids are choosing to eat steak. It’s that it’s in all of the processed foods, as saturated fats and dairy and butter and mixed dishes,” said Deirdre Tobias of Harvard University.
In a similar vein, Christopher Gardner of Stanford University said picking a different kind of meat isn’t going to move the needle enough.
“If we want to make a meaningful difference,” he said, “choosing leaner or the lower fat version isn’t going to get us there.”
Research looking at how people might replace problematic foods high in fats and sodium was a target of the scientific advisers. That’s when limitations of the data emerged, relying on prospective cohort studies to compare a group that ate more plant foods compared to people who ate a lot of red or processed meat. In many cases the evidence wasn’t strong enough to say one particular dietary pattern was the answer, with most conclusions presented Tuesday on beverages, for example, based on moderate or limited evidence.
“Moderate evidence shows that sugar-sweetened beverages are associated with unfavorable growth patterns and body composition and higher risk of obesity in childhood through early adulthood and with unfavorable body composition, higher risk of obesity, and increased risk of type 2 diabetes in adults,” Andrea Deierlein of New York University said.
Looking at the link between saturated fats and cardiovascular disease, the one strong conclusion the committee could make after comparing different dietary patterns was “butter is not back,” Gardner said. “Butter is worse for your LDL cholesterol than all kinds of oils and spreads higher and unsaturated fat. This really isn’t new news. It’s just reinforcing what there’s a large database for.”
In the end, the group did not recommend overturning the 2020 guidelines but did suggest emphasizing the plant-based or plant-forward diets included in those guidelines, as well as the importance of portion size in offering large portions of fruits and vegetables to children.
The advisers did discuss a new element: adding culturally tailored dietary interventions. But here again, the group said more data are needed to define how disparities in diet and related chronic disease outcomes have continued to persist in particular groups.
“Some of the people in eight-week trials are very different than people who don’t get into eight-week trials that may be at very high risk we need to learn more about,” said Angela Odoms-Young of Cornell University, vice chair of the advisory committee. “We might only be getting a cut of the population as far as characteristics that we want to develop interventions for.”
Though nutritional research on different cultural food practices may be sparse, the verdict has long been in on sugar-sweetened beverages and their association with unfavorable health outcomes.
“The next edition should specifically recommend plain drinking water as the primary beverage for people to consume,” the group’s draft says.
“We have the information on sugar-sweetened beverages and now the resources and attention should be shifted over to education,” said Sarah Booth of Tufts University, the committee’s chair. “Sometimes we keep doing the research when the answer is clear, but there isn’t the prioritization of the education.”
The entire draft will be revised, Booth cautioned.
“We still have still more work to do,” said Odoms-Young.
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