A large US cohort study found no overall association between eating more ultra-processed food and developing colorectal cancer among older adults. The result adds nuance to a category that includes everything from processed meats and sugary drinks to some whole-grain breads and dairy products.
The study, published in PLOS Medicine, followed 461,682 participants in the NIH-AARP Diet and Health Study. Participants were ages 50 to 71 when they enrolled in 1995 and 1996, and researchers tracked cancer diagnoses through 2018. Over a median follow-up of 18.8 years, 10,075 participants developed colorectal adenocarcinoma.
What the cancer study found
After adjusting for a range of demographic, lifestyle and dietary factors, the researchers found no meaningful difference in colorectal cancer risk between the highest and lowest fifths of ultra-processed food consumption. The hazard ratio was 0.97, with a 95 percent confidence interval of 0.91 to 1.03.
The broad category concealed differences among foods. Ultra-processed meat intake was associated with higher colorectal cancer risk, while ultra-processed sources of whole grains, fiber, dairy and calcium were associated with lower risk. Those results suggest that the nutritional profile of a food may matter more than whether it falls under the umbrella label of ultra-processed.
The study does not prove that ultra-processed food is harmless. It was observational, so it cannot establish cause and effect, and diet was measured with a food-frequency questionnaire at enrollment. The cohort was also largely older and White, which limits how confidently the findings can be applied to younger or more diverse populations. That is especially important because the study does not resolve why colorectal cancer rates have been rising among younger adults.
A separate look at brain health
A second study published the same day examined a different question in a different population. The cross-sectional study in JAMA Network Open analyzed 8,783 Canadian adults ages 35 to 69 who did not have cardiovascular disease.
Compared with people in the lowest quarter of ultra-processed food consumption, those in the highest quarter had 1.7 percentage points more body fat and 5.7 milliliters more visceral fat surrounding the abdominal organs. They also had 40 percent higher odds of vascular brain injury on imaging.
The researchers did not find a significant association between ultra-processed food intake and performance on the study's cognitive tests. The link with vascular brain injury also changed under alternative definitions of ultra-processed food, making that result less certain.
