For Heather Yeo, MD, a colon and rectal surgeon and an oncologist at Weill Cornell Medicine and NewYork-Presbyterian in New York City, the analysis underscores that not all ultra-processed foods are created equal.
“The type and nutritional quality of food may matter more for colorectal cancer risk than the processing label alone,” says Dr. Yeo, who was not involved in the research. “This study adds nuance to previous research by examining specific food groups and nutrients rather than treating ultra-processed foods as one uniform category.”
Looking Beyond ‘Big Picture’ Results
Published this week in PLoS Medicine, the study was based on responses and outcomes from a national health and diet study that included about 460,000 Americans who were in their fifties through seventies when the study began.
Over an average follow-up period of about 19 years, participants periodically checked in to report on their health and diet, in the latter case via food frequency questionnaires. In that time, just over 10,000 participants reported being diagnosed with colorectal cancer.
When looking at outcomes as a whole, the researchers observed no association between overall ultra-processed food intake and colorectal cancer rates. But a deeper analysis of food questionnaire data revealed that certain ultra-processed foods were connected to a health boost, while others were tied to greater cancer risk. Specifically:
- Each daily serving of ultra-processed meat was tied to an 8 percent higher relative risk of colorectal cancer.
- Each daily serving of whole grains from ultra-processed sources was tied to a 9 percent lower risk.
- Each daily serving of ultra-processed dairy was tied to a 10 percent lower risk.
Lower cancer risk was even more pronounced in relation to fiber and calcium intake. The study authors calculated a 23 percent lower cancer risk for each additional 300 milligrams (mg) of daily calcium and a 28 percent lower risk for each additional 10 g of daily fiber.
The study authors noted that participants reported getting most of their whole grains from ultra-processed sources, mainly breads and breakfast cereals.
“I honestly hadn’t even considered that something like whole-grain bread could fall into the ultra-processed food category,” says Lilian Chen, MD, the chief of colon and rectal surgery at Tufts Medical Center in Boston.
“I think this study reminds us to look beyond the label of ‘ultra-processed’ and consider the types of foods we’re choosing and what they contribute to our overall diet,” says Dr. Chen, who was not involved in the study.
The research team also examined other ultra-processed food subgroups, including soft drinks, baked goods, and candy, but they did not observe any connections with these and colorectal cancer risk, according to the study coauthor Erikka Loftfield, MPH, PhD, the group lead in the population health research program at Queensland Institute of Medical Research in Berghofer, Australia.
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