Following more than 200,000 Americans over four decades, researchers found that healthy diets lowered disease risk and unhealthy ones raised it, whether the foods were ultra-processed or barely touched.
Few phrases have traveled faster through nutrition advice in recent years than “ultra-processed food.” It has become shorthand for nearly everything wrong with the modern diet: the chips, the soda, the shelf-stable snack cakes engineered to be eaten past the point of hunger. Public health campaigns, bestselling books and a growing number of policy proposals have converged on a simple message. Avoid it.
A new analysis presented at NUTRITION 2026, the annual meeting of the American Society for Nutrition, suggests that message may be aimed at the wrong target. Drawing on data from more than 200,000 U.S. adults, researchers at the Harvard T.H. Chan School of Public Health found that the overall nutritional quality of a person’s diet was strongly tied to their risk of heart disease, type 2 diabetes and death. The degree to which their food had been processed, by contrast, made little difference once quality was taken into account.
“While many ultra-processed foods tend to be of poor nutritional quality and should generally be limited or avoided, processing itself is not inherently harmful,” said Xiaowen Wang, a postdoctoral research fellow in the Department of Nutrition at the Harvard Chan School, who presented the findings in National Harbor, Maryland.
Untangling two things that usually travel together
The difficulty with studying ultra-processed food is that it tends to arrive bundled with other problems. Many of the most heavily processed products are loaded with added sugars, sodium and refined carbohydrates, so people who eat a lot of them also tend to have lower-quality diets overall. That makes it hard to tell whether the harm comes from processing as such or simply from eating poorly.
Complicating matters further, not every ultra-processed food is junk. Fortified breakfast cereals, packaged whole-grain breads, canned beans and plant-based dairy alternatives all count as ultra-processed under the most widely used classification scheme, yet many of them supply fiber, vitamins, antioxidants and other beneficial compounds. Meanwhile, plenty of minimally processed foods, white rice and fruit juice among them, are far from ideal.
Wang and her colleagues set out to pull these two variables apart. They drew on three large, long-running studies that together followed more than 200,000 American adults from the 1980s into the 2020s. To gauge diet quality, they used a framework known as the plant-based diet index, which measures how heavily a person’s diet emphasizes plant foods versus animal products and, crucially, distinguishes healthy plant foods from unhealthy ones. To gauge processing, they used the Nova classification system, which sorts foods by how much industrial processing they have undergone.
The study did not focus on vegans or vegetarians. Participants ate a full range of diets. To keep comparisons consistent, however, the analysis concentrated on the plant-derived components of what people ate.
Four kinds of eaters
Using those tools, the researchers sorted participants into four groups. Some ate a healthy diet built largely on ultra-processed foods: think whole-grain breakfast cereal with fortified plant milk, plant-based yogurt, whole-grain bread and canned fruit. Others ate a healthy diet of minimally processed foods, such as oatmeal with fresh fruit and nuts, quinoa salads dressed with olive oil, and homemade lentil soup.
On the other side of the ledger were people eating unhealthy ultra-processed diets, heavy on fast food, French fries, soda, packaged desserts and refined snacks, and those eating unhealthy minimally processed diets, dominated by foods such as white rice, fruit juice, potatoes and homemade desserts made with refined flour and sugar.
Over the decades of follow-up, about half of the participants died or developed heart disease or type 2 diabetes. When the researchers compared the four groups, a clear pattern emerged. Diet quality mattered a great deal: healthy diets were associated with lower risk and unhealthy diets with higher risk. But within each quality category, whether the diet was ultra-processed or minimally processed made almost no difference. The risks were nearly identical.
A problem with the label
The findings point to a weakness in how processing has come to be used as a proxy for healthfulness. The Nova system classifies foods by how they were made, not by what nutrients they contain. As a result, a nutritious food can land in the ultra-processed category while a nutritionally poor one is labeled minimally processed.
Wang argues that this mismatch has practical consequences. “Advising people to universally ‘avoid ultra-processed foods’ can lead to lower diet quality since healthy ultra-processed foods are beneficial and unhealthy minimally-processed foods are detrimental,” she said. Someone who dutifully swaps fortified whole-grain cereal for a bowl of white rice, in other words, may be following the letter of the advice while making their diet worse.
Her recommendation is to shift the focus. People should “focus on what you’re eating overall, not just whether it’s processed,” Wang said. “A healthy plant-based diet rich in whole grains, fruits, vegetables, nuts, legumes and healthy plant oils is beneficial, even if it includes some processed foods.”
Implications for guidelines and industry
Based on the results, Wang suggested that dietary guidelines should keep promoting well-established high-quality eating patterns, such as the Mediterranean diet or healthy plant-based diets, rather than elevating processing level as a primary criterion. She also pointed to a role for the food industry. Encouraging manufacturers to improve the nutritional profile of packaged foods could make healthy eating more convenient and accessible, particularly for people who rely on shelf-stable products because of time, cost or access constraints.
That point carries real weight. Minimally processed diets often demand more time for shopping and cooking and can cost more, which puts them out of reach for many households. If convenient packaged foods can be made genuinely nutritious, the argument goes, the goal of a healthier population becomes more achievable.
“People should prioritize the quality of foods rather than focusing solely on the level of processing,” Wang said. “Aim for more nutrient-dense, high-quality foods to help lower your risk of chronic diseases.”
A preliminary but pointed result
There are important caveats. The findings were presented as a conference abstract, which was selected by an expert committee but has not undergone the full peer review required for journal publication. The American Society for Nutrition stresses that such results should be treated as preliminary until a peer-reviewed paper appears. The study is also observational, meaning it can identify associations but cannot prove that one dietary pattern causes better or worse outcomes.
The work also does not settle the broader debate over ultra-processed foods. Some researchers argue that certain features of industrial processing, such as altered food textures that speed eating, or additives like emulsifiers, may carry risks not captured by nutrient profiles alone. And because the analysis focused on the plant-derived portion of participants’ diets, it does not directly address processed meats, which have been linked to health risks in other research.
Still, the scale and duration of the dataset lend weight to a message that runs against the current of popular nutrition advice. The healthiest choice, the results suggest, is not necessarily the one that came straight from the farm. It is the one that delivers the most nutritional value, wherever it happened to come from.
Featured image: Anna Miller/Tufts University
Endnotes
- Wang, X. Research abstract presented in the “Innovative Diet Patterns Research and Health Outcomes” oral session at NUTRITION 2026, American Society for Nutrition, National Harbor, Maryland, July 28, 2026. (Conference abstract; not yet peer reviewed.)
- American Society for Nutrition. “For long-term health, diet quality matters more than food processing level.” News release via EurekAlert!, July 28, 2026. https://www.eurekalert.org/news-releases/1136477
- Wang, X., and Sun, Q. “Ultra-Processed Foods and the Impact on Cardiometabolic Health: The Role of Diet Quality.” Diabetes & Metabolism Journal 48, no. 6 (2024): 1047–1055.