Erikka Loftfield

Replacing 10% of your ultra-processed food intake with minimally processed options is linked to a 2% lower incidence of bowel cancer, according to our new analysis of data from more than 460,000 US adults.

However, we found no overall association between total ultra-processed food intake and bowel cancer incidence.

That said, intake of wholegrains, fibre, dairy, and calcium from ultra-processed food sources was associated with lower bowel cancer incidence. Eating ultra-processed meats was associated with higher bowel cancer incidence. Ultra-processed foods include store-bought biscuits, instant noodles, sugary drinks, processed meats and chips.

Overall, our findings suggest the label “ultra-processed” alone doesn’t tell the full story about bowel cancer risk. What’s in the food seems to matter. Choosing wholegrains and limiting processed meat aligns with current evidence-based guidance. Researchers and policymakers should avoid treating all ultra-processed foods as one group, as this may mask differences linked to disease risk.

Higher intakes of wholegrains, fibre, dairy, and calcium and lower intakes of processed and red meat have been associated with lower bowel cancer risk. Importantly, these food groups and nutrients are in lots of foods, from minimally processed to ultra-processed (as defined by the Nova classification system).

Prior studies evaluating ultra-processed food intake and bowel cancer risk have yielded inconsistent results, with some showing a higher incidence and others showing no connection. To investigate further, we evaluated data from over 460,000 adults aged 50 to 71 who were cancer-free when enrolling in the NIH-AARP Diet and Health Study in 1995-96.

Participants answered questions regarding demographics, health conditions, and lifestyle factors, including smoking, physical activity, and dietary habits. Eating frequency and portion sizes were used to estimate daily ultra-processed food consumption under the Nova classification system, which groups items from unprocessed foods (Group 1) to industrially formulated ultra-processed foods (Group 4).

Because the questionnaire was not originally designed to assess processing, we validated it against a detailed dietary subset of participants, confirming that the estimates aligned closely.

Participants were followed for cancer incidence for over 20 years, during which more than 10,000 bowel cancer cases were diagnosed. Using statistical models, we adjusted for demographic, lifestyle, and health factors, including physical activity, smoking, and alcohol consumption.

We found that: Higher intake of reconstituted meat products, such as hot dogs, was associated with higher bowel cancer incidence; higher intakes of frozen desserts, fruit yoghurts, breakfast cereals, and mass-produced breads were associated with lower bowel cancer incidence; and swapping 10% of ultra-processed food with an equivalent weight of minimally processed food was linked to a 2% reduction in bowel cancer risk.
As an observational, questionnaire-based study, these results show association rather than direct cause and effect. Nevertheless, they support current dietary guidelines for bowel cancer prevention: eat plenty of fruit, vegetables, wholegrains, and fibre-rich foods while limiting alcohol, red meat, and processed meats.