Ultra-Processed Food and Colorectal Cancer

Picture the cart at checkout: a box of cereal, a loaf of sliced bread, a pack of deli ham. A new study followed 461,682 US adults aged 50 to 71 for a median of 18.8 years. The total amount of ultra-processed food they ate was not tied to their rate of colorectal cancer (PLOS Medicine). Meat told a different story. Meat from ultra-processed sources went with a higher rate, and so did meat from everything else. The food group that pointed the wrong way was the meat.

Who This Helps

This post is for anyone who shops in a hurry and keeps hearing that anything in a package is bad for you. It is also for people on a GLP-1 who are eating less and want each meal to count. If you are under 50, keep in mind that this study enrolled older adults and measured their diets once, in the mid-1990s.

What the study found on ultra-processed food

The study came out on October 15, 2026, in PLOS Medicine, with Erikka Loftfield of the National Cancer Institute as senior author (PLOS Medicine). Her team used the NIH-AARP Diet and Health Study, which signed up adults aged 50 to 71 in 1995 and 1996. Each person filled out a 124-item food survey once, when they joined. Over the years that followed, 10,075 of them were diagnosed with colorectal cancer.

To sort foods, the team used a system called Nova. It ranks foods from minimally processed, like an apple or plain chicken, up to ultra-processed, like packaged snacks, soft drinks and instant noodles (BMJ). The typical person in the study got 43% of their daily calories from what is termed ultra-processed food.

The team compared the fifth of people who ate the most ultra-processed food with the fifth who ate the least. The two groups had almost the same rate of colorectal cancer. The difference was 3%, small enough to be chance. (For the numbers people: hazard ratio 0.97, 95% confidence interval 0.91 to 1.03.)

Meat was the food group that went the other way

The team also split the diet into parts, such as meat, dairy and whole grains. For each part, they checked whether it came from an ultra-processed source (PLOS Medicine). Each extra daily serving of meat from an ultra-processed source went with an 8% higher cancer rate. Each serving of other meat went with a 4% higher rate. Both figures adjust for how much people ate overall. Both links were small, and both held up statistically. The authors call these food-group results exploratory, so treat them as a lead rather than a verdict.

The study did not test processed meat on its own. Its food database files processed meat and unprocessed red meat as separate items, so the team looked at all meat, sorted by processing level, instead. It could say that about 74% of the processed meat people ate came from ultra-processed sources. One subgroup did stand out. People who ate the most "reconstituted meat and fish products" had a 10% higher rate than those who ate the least.

These are relative figures. They describe a rise from a person's starting risk, not a count of extra cases. In this study, about 2.2 in every 100 people got a colorectal cancer diagnosis over the follow-up (our math, from 10,075 cases among 461,682 people). An 8% rise on that starting point is small for any one person.

The World Health Organization's cancer agency, IARC, made its own call years earlier (IARC). It classes processed meat, such as hot dogs, ham, sausages and jerky, as a cause of colorectal cancer. It estimates that each 50 gram portion eaten daily raises the risk by about 18%. IARC says the rating describes how strong the evidence is, not how big the risk is. So it does not put processed meat on a par with smoking.

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Bread and cereal were linked to lower rates

Whole grains, fiber, dairy and calcium from ultra-processed sources were all linked to lower rates of colorectal cancer (PLOS Medicine). About 83% of the whole grains people ate came from ultra-processed foods. People who ate the most ultra-processed bread had a 9% lower rate than those who ate the least. For breakfast cereal, the rate was 16% lower. The authors suggest these opposite pulls may be why the total for ultra-processed food came out flat.

The team also modeled a swap. Shifting 10% of a person's total food weight from ultra-processed to minimally processed food was linked to a 2% lower rate. The authors add a caution. Their data can't show whether fiber or calcium from an ultra-processed food acts the same in the body as it does from a less-processed one.

What this study can't tell you

The study looked at one disease in one group (PLOS Medicine). The people were older and mostly white, they joined in the mid-1990s, and their diet was measured once. The authors write that the findings "may not generalize to younger more diverse populations." Nobody was assigned what to eat. So the study can show a link, but it can't prove that any food causes or prevents cancer. A single survey also can't capture how habits changed over two decades, or how many more ultra-processed foods reached the shelves (ecancer).

Other diseases have their own evidence. A 2024 review in The BMJ pulled together 45 pooled analyses with about 9.9 million participants, counted across overlapping studies (BMJ). All of it was observational. By the review's own grades, the evidence was convincing that more ultra-processed food goes with more deaths from heart disease, 50% higher at the top intake. The same was true for type 2 diabetes. Even so, the review rated the quality of the heart-disease data as very low. The link with death from any cause, 21% higher, sat one grade below. Colorectal cancer sat near the bottom of its scale, in the suggestive and weak classes.

On a GLP-1, each food choice carries more weight

People taking a GLP-1 tend to eat a lot less. Studies have seen calorie intake fall 16% to 39% compared with placebo, according to a 2025 joint advisory from four medical and nutrition groups (Obesity journal advisory). The advisory warns that a drop that large can leave people short on vitamins and minerals. Its diet plan is built on minimally processed foods: fruits, vegetables and whole grains. It says red and processed meats, along with ultra-processed sweets and savory snacks, should be kept to a minimum or avoided. The protein sources it encourages are beans, lentils, dairy, seafood, eggs and lean poultry.

Nobody in the NIH-AARP study was asked about GLP-1 medications, so read this as general nutrition context and not as a plan for you. If you compare protein by the label, our post on why 20 grams of protein on the box is not always 20 grams your body can use explains what the number leaves out.

Final Takeaway

In this study of older US adults, eating more ultra-processed food overall was not tied to more colorectal cancer. Bread and breakfast cereal were tied to slightly less. Meat went the other way, whatever its source, and the authors call that result exploratory. None of this clears ultra-processed food on heart disease or diabetes, where a separate review points the other way. If you are on a GLP-1 and eating less, the 2025 advisory's advice stands. Build meals on minimally processed foods, and keep processed meat to a minimum.

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Frequently Asked Questions

Does this study mean ultra-processed food is safe to eat?

No. It looked only at colorectal cancer, in US adults who were 50 to 71 when they joined in the mid-1990s. A 2024 review of earlier research linked more ultra-processed food to a higher risk of death from heart disease and to type 2 diabetes. The new study speaks to one cancer in one older group, so it doesn't settle the wider question for people on a GLP-1 or anyone else.

Which meat was linked to colorectal cancer in the new study?

Meat from both ultra-processed and other sources was linked to higher colorectal cancer rates in older US adults. Per daily serving, meat from ultra-processed sources went with an 8% higher relative rate, and meat from other sources with a 4% higher rate. The authors call these food-group results exploratory. The study did not test processed meat on its own, but the World Health Organization's cancer agency classes processed meats like hot dogs, ham and sausages as a cause of colorectal cancer.

Does this apply to people taking a GLP-1 medication?

Not directly, because the study did not ask about GLP-1 medications and its participants were older US adults whose diets were measured in the 1990s. People on a GLP-1 tend to eat much less, so each food they choose supplies more of their nutrition. A 2025 nutrition advisory for GLP-1 users recommends minimally processed foods and keeping red and processed meats to a minimum.