New study: The unhealthy eating habit that may increase men’s risk of colon cancer by 29%

According to a new study published in The BMJ. And while highly processed foods may increase cancer risk for men, the same correlation has not been found in women.

The August 2022 study analyzed data from three major surveys of health professionals conducted between 1986 and 2015, including the Nurses’ Health Study I and II and the Health Professionals Follow-Up Study. Participants completed questionnaires at baseline and every two years thereafter to collect information about their eating habits, lifestyle, cancer diagnoses, and demographic characteristics. After excluding those with incomplete responses or a previous diagnosis of cancer, the new analysis included 159,907 women and 46,341 men.

Participants were then placed into quintiles based on their consumption of ultra-processed foods — from lowest to highest intake — and researchers were matched for race, family cancer history, smoking status, physical fitness and menopausal status. Their findings: Men in the top quintile of processed foods were 29% more likely to develop colon cancer than men in the bottom quintile. No association was observed between total ultraprocessed food consumption and colorectal cancer risk among female participants.

Why the gender gap?

The study’s authors theorized that the different patterns of cancer risk in men and women might be related to obesity and sex hormones.

“In men and postmenopausal women, estrogen is primarily produced in adipose tissue. In women, a high estrogen-to-testosterone ratio may reduce the risk of colorectal cancer, while in men it may increase the risk of colorectal cancer,” the authors write.

Another possible explanation the researchers offered concerns the nutritional makeup of the specific types of ultra-processed foods that men and women consumed. Processed meat, poultry, and fish-based ready-to-eat products and sweetened beverages were associated with a higher risk in men.

However, among female participants, the authors noted that in the highly processed category of yogurt and dairy-based desserts, relatively healthier food choices may have been made, “and therefore protective effects (e.g., due to higher calcium levels) may outweigh adverse effects ( for example through higher sugar levels),” they explained.

Why are ultra-processed foods bad for the colon?

This new evidence adds to a long-standing concern about the harmful effects of ultra-processed foods on human health. Dozens of previous studies have shown that these products — heavily modified with sugar, salt, and fat — increase the risk of diabetes, cardiovascular disease, irritable bowel syndrome, and obesity.

“We initially thought that colorectal cancer might be most affected by diet compared to other cancers,” said Lu Wang, lead author of the study and a postdoctoral fellow in the Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy at Tufts University. “Processed meat, most of which falls into the ultra-processed food category, is a strong risk factor for colon cancer. Highly processed foods are also high in added sugars and low in fiber, which contribute to weight gain and obesity, and obesity is an established risk factor for colon cancer.”

The study authors also explain that along with the poor nutritional composition of ultra-processed foods, these products often contain additives — like emulsifiers and artificial sweeteners — that can inflame the gut microbiome and lead to the growth of cancerous polyps in the colon.

“Ultra-processed foods may also contain contaminants that migrate from plastic packaging, such as bisphenol A, which the European Chemicals Agency classifies as a “substance of very high concern,” the study authors noted.

Colorectal cancer is the third most commonly diagnosed cancer worldwide, claiming more than 900,000 lives every year.

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