New Study Ties Ultra-Processed Meats to Higher Colorectal Cancer Risk

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.

Why Processed Meats May Be Riskier Than Fiber and Dairy

Distinct chemical additives in ultra-processed foods affect the bowel in different ways, which likely contributes to their varying health effects, according to Megan Delisle, MD, MPH, a colorectal surgical oncologist at Moffitt Cancer Center in Ruskin, Florida.

“For example, meats contain preservatives such as nitrates and nitrites as well as a form of iron called ‘heme iron’ that can cause inflammation of the colon and damage to the DNA of the colon,” says Dr. Delisle, who was not involved in the study.

In contrast, she notes that fiber feeds beneficial gut bacteria, and calcium binds to compounds in the colon that can cause irritation and inflammation, and helps to minimize the negative effects of those compounds.

Rising Colorectal Cancer Among Young Adults Requires More Research

These latest findings align with previous research indicating that certain nutrients support colon health while others may be detrimental. Cancer experts interviewed here each noted the large participant group size and years of follow-up as significant strengths supporting prior studies on the subject. Still, the research was limited because it relied on self-reported data, which is prone to error. Additionally, because the analysis was observational, it can only identify associations. It doesn’t prove that a particular food caused or prevented cancer.

“The increase in early onset is complex and is likely multifactorial,” says Dr. Yeo, who stresses the need for more research on this concerning trend.

Lifestyle Changes May Help Lower Risk

Colorectal cancer is the third most commonly diagnosed cancer in the United States, and the foods we eat appear to influence the odds of getting the disease.

To lower your cancer risk, experts advise the following.

• Prioritize whole foods. Focus on eating fresh whole grains, fruits, vegetables, beans, lentils, fish, and other healthy protein sources.
• Limit processed meats. This study did not identify a safe amount of ultra-processed meat, and it wasn’t designed to compare specific swaps, such as replacing processed meat with fish, poultry, or plant-based foods, according to Dr. Loftfield. The American Cancer Society, however, advises eating processed meat "sparingly, if at all.”

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• Drink less alcohol. Alcohol is another risk factor for colorectal cancer.

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• Stay fit. Get regular exercise and reduce excess weight. Inactivity and obesity are also associated with increased cancer risk.

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• Get screened. Keep up with recommended colorectal cancer screening. “For most adults at average risk, screening should begin at age 45, and some people may need to start earlier based on their risk factors,” says Dr. Chen. “If you have a family history of colorectal cancer, concerning symptoms, or questions about your individual risk, talk with your doctor rather than waiting until you’re due for routine screening.”