Researchers found no overall association between eating more ultra-processed foods and developing colorectal cancer.
Ultra-processed whole grains and dairy products were associated with lower cancer rates, while processed meats were associated with higher rates.
The findings suggest that a food's nutritional content may matter more than its level of processing when considering colorectal cancer risk.
Ultra-processed foods have developed a reputation as something consumers should avoid. From packaged snacks and frozen meals to breakfast cereals and other convenience foods, these products are often criticized for their ingredients and potential effects on long-term health.
Some research has also raised concerns about a possible connection between ultra-processed foods and colorectal cancer. However, a new study suggests that the relationship may not be as straightforward as many people think.
Published in PLOS Medicine, the research found no overall association between higher ultra-processed food consumption and colorectal cancer. Instead, the researchers discovered that different types of ultra-processed foods had very different associations with cancer rates.
Researchers followed more than 460,000 adults
To investigate the potential connection, researchers analyzed information from 461,682 adults who participated in the NIH-AARP Diet and Health Study. Participants were between 50 and 71 years old when they enrolled in 1995 and 1996.
At the beginning of the study, participants completed questionnaires about their eating habits, including how often they consumed different foods. Researchers used this information to estimate how much ultra-processed food each person typically ate.
The team then followed participants through 2018, tracking new cases of colorectal cancer over a median period of 18.8 years.
During that time, researchers identified 10,075 cases of colorectal adenocarcinoma, a common type of colorectal cancer. They also considered other factors that could influence cancer risk, including participants' ages, physical activity levels, smoking habits, alcohol consumption, and education.
What the findings mean for your grocery shopping
The biggest takeaway was that eating more ultra-processed food overall was not associated with a higher incidence of colorectal cancer.
However, the results changed when researchers looked at specific food groups. Higher consumption of whole grains, fiber, dairy products, and calcium from ultra-processed food sources was associated with lower colorectal cancer incidence. Meanwhile, greater consumption of processed meats from ultra-processed sources was associated with higher incidence.
Researchers also found that replacing 10% of ultra-processed food intake by weight with minimally processed foods was associated with a 2% lower incidence of colorectal cancer.
For consumers, the findings suggest that labeling a food as ultra-processed doesn't necessarily tell the whole story. Its nutritional content and ingredients may be more useful considerations when making food choices.
Still, there are some important limitations. Participants reported their diets only at the beginning of the study, meaning researchers couldn't account for changes over nearly two decades. The study was also observational, so it cannot establish that particular foods directly cause or prevent cancer.
The researchers say the findings support existing dietary guidance: prioritize whole grains, fiber, dairy, and calcium while limiting processed meat. In other words, consumers may benefit more from looking at what's actually in their food than relying on processing labels alone.