Large NIH-AARP study finds no link between total ultra-processed food intake and colorectal cancer

What the study found

A study published Oct. 15 in PLOS Medicine found no association between total ultra-processed food intake and colorectal cancer among 461,682 adults in the NIH-AARP Diet and Health Study. Comparing the highest fifth of intake with the lowest, the hazard ratio was 0.97, with a 95% confidence interval of 0.91 to 1.03. ^{[1] [2]}

"We did not observe an association between total ultra-processed food (UPF) intake and colorectal cancer incidence," senior author Erikka Loftfield said in a news release quoted by Healthline. Loftfield led the work at the National Cancer Institute and is now at QIMR Berghofer in Brisbane. ^{[2] [3] [1]}

Opposite signals inside the category

The null overall result masked differences between food groups. Higher intake of ultra-processed bread (hazard ratio 0.91), breakfast cereals (0.84) and frozen desserts and milk drinks (0.82) was associated with lower risk, while reconstituted meat and fish products were associated with higher risk (1.10). ^[1]

When the researchers split foods by whether they came from ultra-processed sources, whole grains, fiber, dairy and calcium were linked to lower risk and meat to higher risk in both cases. The authors wrote that these opposing associations may explain the overall null finding and that the results line up with existing guidance to eat whole grains, fiber and dairy and limit processed meat. ^{[1] [2]}

"A whole grain cereal and a hot dog are both UPF, but they push risk in opposite directions," Ketan Thanki, a colorectal surgeon at MemorialCare Todd Cancer Institute who was not involved, told Healthline. Marissa Shams-White of the American Cancer Society told the outlet that classifying foods only by processing level "may not tell the whole story." ^[2]

How the study was done

Participants, aged 50 to 71 and cancer-free when they enrolled in 1995 and 1996 in six states and two metropolitan areas, completed a 124-item food frequency questionnaire. Researchers classified foods with the Nova system and followed participants through 2018, a median of 18.8 years, during which 10,075 colorectal adenocarcinomas were diagnosed. Median ultra-processed intake was about 43% of daily calories. ^[1]

The authors list several limitations: diet was measured once and self-reported, the questionnaire was not designed to capture processing, additives were not assessed, the cohort was older and mostly white, and residual confounding is possible. Hattie Wright of the University of the Sunshine Coast told Australia's Science Media Centre that the study "can't show that these foods directly cause or protect against colorectal cancer." ^{[1] [3]}

How it fits with earlier research

The result differs from a 2022 BMJ study of three US cohorts, which found men with the highest ultra-processed intake had a 29% higher risk of colorectal cancer (hazard ratio 1.29), with no significant link in women. ^[4]

A 2025 JAMA Oncology study from Mass General Brigham found women in the Nurses' Health Study II with the highest intake had a 45% higher risk of early-onset conventional adenomas, the precancerous polyps that can lead to colorectal cancer before age 50. ^[5]