The nutritional quality of a person’s diet predicted heart disease, type 2 diabetes and death across more than 200,000 US adults, while the level of industrial food processing did not, according to a Harvard analysis presented July 28 at NUTRITION 2026 in National Harbor, Maryland. Xiaowen Wang, PhD, a postdoctoral research fellow in the Department of Nutrition at the Harvard T.H. Chan School of Public Health, led the work.
The finding cuts against the advice that has dominated nutrition messaging for years: avoid ultra-processed food, full stop.
Key takeaways
- Within each level of diet quality, risk was about the same whether the food was factory made or cooked at home.
- Healthy diets lowered risk and unhealthy diets raised it, regardless of processing level.
- This is a conference abstract, not a peer-reviewed paper, and the study was observational.
What the study found
Wang’s team pooled three long-running US cohort studies that together followed more than 200,000 adults from the 1980s through the 2020s, according to a report from Earth.com.
Each person’s food was scored twice. Once for nutritional quality, using the plant-based diet index. Once for industrial processing, using the Nova classification. Participants did not have to be vegetarian, and the analysis looked only at the plant-derived part of each diet.
Crossing those two scores created four groups: healthy foods in ultra-processed form, such as fortified cereal, packaged whole-grain bread and canned fruit; healthy foods with almost no processing, such as oatmeal with fresh fruit and nuts; unhealthy ultra-processed foods, such as fast food, fries, soda and packaged desserts; and unhealthy minimally processed foods, such as white rice, fruit juice, potatoes and cakes baked at home from refined flour.
About half the participants died or developed heart disease or type 2 diabetes during follow-up.
Diet quality split the groups cleanly, and the pattern held across all three outcomes. Processing level did not. “Within each quality band, the risks were nearly identical whether the food came from a factory or a home kitchen,” Earth.com reported.
“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,” Wang said.
Dr. Kumar’s take
Here is the methodological point I think most coverage will skip.
Nutritional quality and processing level travel together in the real world. Most ultra-processed products are loaded with added sugar, sodium and refined starch, so people who eat a lot of them have worse diets overall. That means the long line of studies linking ultra-processed food to disease were, in large part, measuring sugar, salt and refined carbohydrate and calling the result “processing.” This analysis is an attempt to pull the two apart.
Nova is a manufacturing taxonomy. It sorts food by how it was made, not by what it does to you. A vitamin-fortified whole-grain cereal and a can of soda land in the same bucket. That is a strange metric to hang policy on, and yet Nova categories keep showing up in dietary guidelines and proposed labeling rules. This study argues the metric is being asked to do a job it was never validated for.
I am not reading this as “ultra-processed food is fine.” Two caveats matter. First, this is an unpublished conference abstract. No peer review, no full methods, no risk figures released yet. Abstracts get revised, and some never publish at all. Second, it is observational. People chose their own diets over decades, which is not the same as testing processing under controlled conditions.
A 2019 inpatient trial of 20 adults, cited alongside this work, fed people ultra-processed and unprocessed diets for two weeks each, matched for calories, sugar, fat, fiber and macronutrients. People ate about 500 extra calories a day on the ultra-processed diet and gained weight. Processing may still change how much you eat even when the nutrients are held constant. Both things can be true.
Food quality is the signal. Processing is a rough proxy that sometimes tracks it and sometimes does not.
What it means for you
Stop doing the processing check at the grocery store and start doing a nutrition check. Canned beans and fortified whole-grain cereal are ultra-processed by the Nova definition and are still good food. Soda, fries and packaged desserts are the problem, and so is a cake you bake yourself from white flour and sugar.
“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.”
That lines up with the broader evidence, including work showing a plant-based diet lowered heart disease risk over 20 years. The composition of the diet does the work.
If canned lentils or frozen fruit is what gets more plants onto your plate on a busy weeknight, take the shortcut. The label on the box is not the thing raising your risk.