A large observational study has found no overall association between ultra-processed food consumption and colorectal cancer, also known as bowel cancer. Led by Erikka Loftfield of the National Cancer Institute and published in PLOS Medicine on 15 October, the research analysed dietary and health records from 461,682 Americans. Participants were aged 50 to 71 when they entered the NIH-AARP Diet and Health Study in 1995 and 1996. They were followed through 2018, with a median follow-up of 18.8 years. Ultra-processed products account for more than half of the calories consumed by American adults, but encompass nutritionally diverse foods.
Although total consumption was not associated with higher cancer incidence, analysis by food category revealed contrasting patterns. Greater intake of ultra-processed wholegrain and dairy products was associated with lower incidence, whereas meat from ultra-processed sources was associated with higher incidence. A substitution analysis also linked replacing 10% of ultra-processed food intake, measured by weight, with minimally processed alternatives to a 2% lower incidence. Taken together, the findings suggest that nutritional composition may be more informative than processing classification alone when assessing these associations.
Important limitations constrain interpretation. Participants were predominantly older, white Americans, which may limit applicability to younger and more diverse populations. Dietary intake was assessed only at enrolment, preventing researchers from accounting for subsequent changes. Meanwhile, the increasing availability and variety of ultra-processed products may have led those initial assessments to underestimate consumption during follow-up. As an observational investigation, the study cannot establish causation. Its findings nevertheless align with existing dietary guidance favouring wholegrains and dairy products while limiting processed meat, rather than treating all ultra-processed foods as equally harmful.
