Ultra-processed foods as a category don't raise colorectal cancer risk, major NCI study finds

Ultra-processed foods — everything from whole-grain cereal to hot dogs — now account for more than half of the energy Americans consume each day. For years, researchers have debated whether that fact alone should alarm us about colorectal cancer. A large new study from the National Cancer Institute says, on its own, it should not.

Published October 15 in PLOS Medicine, the study tracked 461,682 U.S. adults aged 50 to 71 for a median of nearly 19 years and found no meaningful association between total ultra-processed food intake and colorectal cancer incidence. The hazard ratio comparing the highest to the lowest quintile of consumption was 0.97 — statistically indistinguishable from no effect (95% CI 0.91–1.03; P trend = 0.55). Over the follow-up period, 10,075 cases of colorectal adenocarcinoma were diagnosed.

We did not observe an association between total ultra-processed food (UPF) intake and colorectal cancer incidence. However, when we looked at food groups, like whole grains, dairy, and meat, by UPF or non-UPF source, we found that associations were in line with current dietary guidance for colorectal cancer prevention.— Erikka Loftfield, PhD, former investigator, National Cancer Institute

The null overall finding, the researchers argue, may itself be the most informative result: it likely reflects the fact that the ultra-processed category contains foods that push colorectal cancer risk in opposite directions, canceling each other out in aggregate analyses. UPF sources of whole grains, fiber, dairy, and calcium were each inversely associated with colorectal cancer incidence. UPF meat sources were positively associated with it. The researchers also found that replacing 10% of gram weight from ultra-processed food intake with minimally processed foods was associated with a 2% lower incidence of colorectal cancer.

A whole grain cereal and a hot dog are both UPF, but they push risk in opposite directions.— Ketan Thanki, MD, colorectal surgeon, MemorialCare Todd Cancer Institute at Long Beach Medical Center

That tension — a single label covering foods with sharply different health profiles — is the central challenge the study surfaces. Experts not involved in the research said the NCI team's approach of breaking ultra-processed foods into subgroups by food type is more illuminating than treating the category as a monolith.

While the study did not find that overall ultra-processed food intake was associated with colorectal cancer risk, the findings suggest that simply classifying foods by their level of processing may not tell the whole story. One of the challenges with studying ultra-processed foods is that the category includes a very wide range of foods and beverages, and we don't yet know whether they all relate to colorectal cancer risk in the same way.— Marissa Shams-White, PhD, senior principal scientist in population science, American Cancer Society

Just because it is ultra-processed doesn't mean it is inherently bad or good for you. The source of the food and the additives like preservatives, flavorings, sugars, and pigments that are added to increase palatability probably play a much larger role in increasing cancer risk.— Ketan Thanki, MD, colorectal surgeon, MemorialCare Todd Cancer Institute at Long Beach Medical Center

The study draws on the NIH-AARP Diet and Health Study, in which participants aged 50 to 71 enrolled between 1995 and 1996 and self-reported their diets using a food frequency questionnaire. Median ultra-processed food consumption was 293 grams per 1,000 kilocalories per day, or 43% of daily energy intake. Researchers used the Nova classification system to categorize foods by level of processing and applied multivariable-adjusted Cox proportional hazards regression models, controlling for age, sex, race and ethnicity, education, physical activity, smoking, and alcohol use.

The authors are candid about the study's limits. Participants were primarily older, white Americans, restricting how broadly the findings can be applied. Crucially, dietary intake was measured only once at enrollment in 1995–96, meaning the data cannot capture how eating habits shifted over nearly two decades — or account for the expanding availability of ultra-processed products since then.

The new findings do not resolve the broader debate. Earlier research has pointed in different directions depending on the population studied. A 2022 study found that men in the highest quintile of ultra-processed food consumption faced a 29% higher risk of colorectal cancer than those in the lowest quintile, according to MedPage Today. A separate study published in JAMA Oncology — also covered by MedPage Today — found that among more than 29,000 female nurses, those in the highest quintile of ultra-processed food intake had a 45% higher risk of early-onset conventional adenomas (precancerous growths diagnosed before age 50) compared with those in the lowest quintile (adjusted OR 1.45; 95% CI 1.19–1.77). That study, led by Andrew T. Chan, MD, MPH, of Massachusetts General Hospital and Harvard Medical School, focused specifically on early-onset precursors — a distinct question from overall colorectal cancer incidence across all ages.

The current evidence remains limited and inconsistent. More research in diverse cohorts is needed to determine whether sex modifies this relationship.— Caroline Um, PhD, MPH, American Cancer Society

For now, the practical guidance from multiple experts converges on reading ingredient labels rather than relying on processing classifications, and on established dietary patterns: emphasizing whole grains, fruits, vegetables, fiber, dairy, and calcium while limiting processed and red meats, sugar-sweetened beverages, refined grains, and alcohol. The American Cancer Society estimates approximately 108,000 new cases of colon cancer and nearly 50,000 new cases of rectal cancer will be diagnosed in the United States in 2026.

You shouldn't just go by whether a food is designated as ultra-processed. You should go by what's on the [ingredient] label.— Ashkan Farhadi, MD, gastroenterologist, MemorialCare Orange Coast Medical Center

Why it matters — With ultra-processed foods making up more than half of what Americans eat, the finding that the category label alone doesn't predict colorectal cancer risk — but specific foods within it do — has direct implications for how dietary guidelines are written and how individuals should read food labels.

Sources differ on Whether ultra-processed food consumption raises colorectal cancer risk: No overall association found in adults aged 50–71 over ~19 years (HR 0.97, not significant) (journals.plos.org) vs Men in highest UPF quintile had 29% higher colorectal cancer risk than those in lowest quintile (2022 study) (medpagetoday.com) vs Female nurses in highest UPF quintile had 45% higher risk of early-onset conventional adenomas before age 50 (adjusted OR 1.45) (medpagetoday.com)

Reported by ecancer.org, journals.plos.org, healthline.com, medpagetoday.com