On Thursday, researchers led by the National Cancer Institute published a study in PLOS Medicine. It found no link between how much ultra-processed food people ate overall and their risk of colorectal cancer. The team tracked 461,682 Americans aged 50 to 71 for a median of almost 19 years. Of those, 10,075 got the disease. Ultra-processed foods are made with ingredients or methods home cooks don't use, like soda, packaged snacks, mass-produced bread, and hot dogs. But specific foods pointed in opposite directions. Meat from ultra-processed sources, like hot dogs, was linked to higher risk. Whole grains, fiber, dairy, and calcium from ultra-processed sources were linked to lower risk. Earlier studies have found mixed results. Colorectal cancer is now the leading cause of cancer death for Americans under 50, according to the American Cancer Society.

1. The Label Hides What's Actually in the Food (Erikka Loftfield, Ketan Thanki, Lilian Chen, Heather Yeo)

One of the study's authors and several surgeons say what's in a food matters more than how it was made.

Calling something "ultra-processed" doesn't tell you enough. Erikka Loftfield is one of the study's authors. She worked on it at the National Cancer Institute and now works at QIMR Berghofer, a research institute in Australia. In The Conversation, she wrote that "the label 'ultra-processed' alone doesn't tell the full story about bowel cancer risk. What's in the food seems to matter." She said researchers and policymakers should stop treating all ultra-processed foods as one group.

A hot dog and whole-grain cereal get the same label. Dr. Ketan Thanki is a colorectal surgeon at the MemorialCare Todd Cancer Institute in Long Beach, California. "A whole grain cereal and a hot dog are both UPF, but they push risk in opposite directions," he told Healthline. People in the study got most of their whole grains from ultra-processed breads and breakfast cereals.

One surgeon was surprised by what counts. Dr. Lilian Chen is chief of colon and rectal surgery at Tufts Medical Center. She told Everyday Health she "hadn't even considered that something like whole-grain bread could fall into the ultra-processed food category." Dr. Heather Yeo, a colorectal surgeon at Weill Cornell Medicine, said the type and quality of food "may matter more for colorectal cancer risk than the processing label alone."

2. Either Way, the Findings Weren't New (Beverley O'Hara, Gunter Kuhnle)

Two nutrition scientists say the meat and fiber findings were already established.

This study only confirmed what scientists already knew. Dr. Beverley O'Hara is a lecturer in public health nutrition at Leeds Beckett University in England. She told the Science Media Centre that the meat, fiber, and whole-grain findings "are already firmly established." She said sorting foods by processing "adds nothing new."

One critic calls this kind of study "research waste." O'Hara said applying the processing label to old diet surveys "could be said, in my opinion, to constitute 'research waste'." She said the money would be better spent on other kinds of studies.

Diet quality tracked with cancer, and processing didn't. Gunter Kuhnle is a professor of nutrition and food science at the University of Reading. He said the study showed that "in contrast to processing and ultra-processing, diet quality is strongly associated with colorectal cancer risk." He said that confirms what was already known about low-fiber diets heavy in processed meat. He also said the diet surveys "have not been designed to estimate UPF intake." The authors "took great care to address this limitation, but it is still a serious limitation," he said.

Other scientists say the study couldn't measure what worries people, so it can't clear these foods.

The survey couldn't measure additives like emulsifiers. Dr. Rosiered Brownson-Smith is a postdoctoral nutrition researcher at King's College London. She told the Science Media Centre that food questionnaires "are poor at distinguishing degrees of processing" and "cannot capture exposure to specific additives such as emulsifiers." "A null result for total UPF here is therefore not evidence that UPFs are harmless," she said.

The study's own authors flag the same gaps. People reported their diets once, in the mid-1990s. The paper says the survey was built to measure nutrients, not processing. It says the team couldn't study additives because it had no ingredient-level data. The authors wrote that they "likely underestimate current UPF intake levels." They said this "may also contribute to observed null findings."

The study says nothing about younger adults. Brownson-Smith said people shouldn't apply the results to younger adults, given "the rise in early-onset colorectal cancer, which this study cannot speak to." Jules Griffin directs the Rowett Institute at the University of Aberdeen in Scotland. He noted that people eat more ultra-processed food than when the study began, "particularly in young adults."

Where This Lands

Scientists agree that meat from ultra-processed sources went with higher risk in this study. They split over what the missing link for ultra-processed food as a whole means. Loftfield says the label alone doesn't tell the full story, and what's in the food seems to matter. O'Hara says sorting foods by processing added nothing new. Brownson-Smith says a null result doesn't show these foods are harmless, and the study can't speak to the rise in younger patients.

Sources