A study of more than 460 000 Americans found that ultra-processed foods (UPF) were not associated with increased colorectal cancer risk overall, challenging a widely-held assumption. The study team found that while processed meat was linked to higher cancer incidence, ultra-processed wholegrains and dairy products were associated with lower incidence.
The research, led by Erikka Loftfield of the National Cancer Institute and published in PLOS Medicine, suggests that the health effects of ultra-processed foods may depend heavily on what those foods actually contain.
Ultra-processed foods have attracted increasing scrutiny because of their potential connections to chronic diseases, including colorectal cancer (CRC). Yet the category includes a remarkably diverse assortment of foods, making it difficult to judge their health effects as a single group.
For example, some ultra-processed whole grain and dairy products have been associated with a lower risk of colorectal cancer, while processed meats have been linked to a higher risk. This raises an important question about whether the level of processing alone is a useful indicator of a food’s potential health effects.
Cancer risk tracked for 19 years
To investigate these differences, researchers examined health and dietary records from 461 682 Americans aged between 50 and 71 when they joined the NIH-AARP Diet and Health Study in 1995 and 1996.
At the start, participants completed questionnaires describing how frequently they ate different foods. Researchers used these responses to estimate each person’s intake of ultra-processed foods.
Participants were then tracked until 2018, with a median follow-up period of 18.8 years. This allowed the team to examine how dietary patterns were associated with the development of colorectal cancer over nearly two decades.
The results showed no overall association between total ultra-processed food consumption and colorectal cancer incidence. In other words, participants who consumed more ultra-processed foods did not, as a group, experience higher rates of colorectal cancer.
However, a closer examination of individual food categories revealed a much more complicated picture.
The researchers found that higher consumption of wholegrains, fibre, dairy products, and calcium from ultra-processed food sources was associated with a lower incidence of colorectal cancer.
Meat from ultra-processed sources showed the opposite pattern, with greater consumption associated with higher cancer incidence.
The team also examined what might happen when ultra-processed foods were replaced with less processed alternatives. Their analysis found that substituting minimally processed foods for 10% of ultra-processed food intake by weight was associated with a 2% lower incidence of colorectal cancer.
These findings suggest that the nutritional characteristics of individual foods may be more informative than simply classifying everything as ultra-processed. Foods placed in the same broad category can have very different associations with cancer risk.
Important limitations
Despite the study’s large size and lengthy follow-up period, the researchers caution that its conclusions may not apply equally to everyone.
Most participants were older, white Americans, meaning the findings may not accurately reflect the experiences of younger adults or more racially and ethnically diverse populations.
Another important limitation involves how dietary information was collected. Participants reported their eating habits only once, at the beginning of the study. Researchers therefore could not account for changes in individual diets over the following decades.
The availability and variety of ultra-processed foods also increased during that time. As a result, the initial dietary assessments may have underestimated participants’ actual consumption during the study period.
Because the research was observational, it also cannot establish whether particular foods directly increase or decrease cancer risk.
What the results mean for a healthy diet
Rather than treating all ultra-processed foods as equally harmful, the findings support evaluating foods according to their nutritional content and specific health associations.
The results also align with existing dietary recommendations for colorectal cancer prevention, which encourage eating wholegrains, fibre, dairy products, and calcium-rich foods while limiting processed meat.
“Ultimately, the study highlights why the label ‘ultra-processed’ may not tell the whole story. When it comes to colorectal cancer, the kinds of foods people eat appear to matter more than their processing category alone,” observes Loftfield.
Study details
Associations of food processing and dietary risk factors with colorectal cancer incidence in the NIH-AARP Diet and Health Study: A cohort study
Leila Abar, Caitlin O’Connell, Hyokyoung Hong et al.
Published in PLOS Medicine on 15 October 2026
Abstract
Background
Ultra-processed foods (UPF) account for >50% of energy intake by US adults. UPF intake can include dietary components linked to lower colorectal cancer (CRC) risk, such as wholegrain and dairy products, and others linked to higher CRC risk, such as processed meats, potentially explaining the heterogeneity of evidence for an association between UPF and CRC risk. Our goal was to estimate the associations of UPF and established CRC-related dietary factors, by UPF and non-UPF source, with CRC incidence in a large cohort study.
Methods and findings
US adults, aged 50–71, who enrolled in the NIH-AARP Diet and Health Study in 1995–96, self-reported dietary intake using a food frequency questionnaire (FFQ). Median UPF intake was 293 g/1000 kcal/day or 43% of daily energy intake. We assigned disaggregated FFQ items to Nova classification and categorised UPF intake (g/1000 kcal/day) into sex-specific quintiles. Participants who were cancer-free at baseline (N = 461,682) were followed for cancer incidence through 2018, and 10,075 colorectal adenocarcinoma cases were diagnosed. We used multivariable-adjusted Cox proportional hazards regression models, adjusted for demographic, lifestyle, and health-related factors, including age, sex, race/ethnicity, education, physical activity, smoking, and alcohol drinking, to estimate associations for UPF and related dietary components with CRC incidence. UPF intake was not associated with CRC incidence (hazard ratio 5th versus 1st quintile 0.97; 95% confidence interval [0.91–1.03]; ptrend = 0.55). Whole grain, fibre, dairy, and calcium intakes from UPF sources were inversely but meat intake from UPF sources was positively associated with CRC incidence. The main limitations of the study relate to its observational design and include potential residual confounding and exposure misclassification owing to systematic or random error in self-reported dietary data.
Conclusions
Total UPF intake was not associated with incident CRC in this cohort of older, US adults. This may be explained, in part, by opposing associations of some UPF with CRC risk. Our findings support current dietary guidance to consume wholegrains, fibre, dairy, and calcium and avoid processed meat for CRC prevention.
See more from MedicalBrief archives:
US studies show colorectal cancer link to ultra-processed foods
Why colorectal cancers are rising in young people – US nurses’ study