AICR’s most recent report found a strong connection between dietary habits and risk of colorectal cancer. And now comes a large study that adds important insights to this research, suggesting that men and women who regularly eat foods linked to chronic inflammation have a greater risk of developing colorectal cancer compared to people who eat anti-inflammatory foods.
In this new study, scientists scored the inflammatory diet potential among approximately 121,000 health care professionals using an index based on 18 food groups. The Empirical Dietary Inflammatory Pattern (EDIP) index links each of these food groups to levels of three inflammatory markers. Coffee, carrots, squash, tea and green leafy vegetables, all ranked as having more anti-inflammatory potential; processed meats, red meats, sugary beverages and refined grains ranked as pro-inflammatory. Participants reported what they ate and other lifestyle habits about every four years.
Current research most strongly supports aiming to meet recommendations for total dietary fiber, yet different types of fiber offer unique benefits.
After an average of 26 years, the study found that men and women eating the most pro-inflammatory diets had a higher incidence of colorectal cancer compared to those eating the most anti-inflammatory diet. Colorectal cancer risk was 44 percent higher in men and 22 percent higher in women during the period of the study. This was after taking into account age, family history, physical activity, smoking and several other recognized risk factors for this cancer.
The study was published in JAMA Oncology.
In a separate analysis that adjusted for BMI – a possible confounder of the association between dietary inflammatory potential and colorectal cancer risk – the risk of developing colorectal cancer was even higher among overweight or obese men. Excess body fat has a clear link to chronic inflammation and is a cause of 11 cancers, including colorectal cancer.
Interestingly, elevated risk was seen among men and women not consuming alcohol. Alcohol is an independent risk factor for colorectal cancer. These findings imply that alcohol may influence colorectal cancer risk by mechanisms other than those of the inflammatory potential of the diet, says Fred K. Tabung, of the Harvard T.H. Chan School of Public Health and the study’s lead author.
This is an observational study so it does not prove cause and effect. And while the EDIP included several markers of inflammation, not all may affect cancer risk in the same way. Also, the EDIP is only one of many ways of looking at dietary eating patterns and it has some quirky rankings that need more research. Pizza, for example, is considered as an anti-inflammatory food.
Yet this study provides further support to the view that a dietary pattern replete in red meat, processed meat, refined grains and sugary beverages is associated with a higher risk of colorectal cancer. It also provides support to the theory that diet-related inflammation may partly mediate the link between dietary patterns and colorectal cancer risk.
Excluding skin cancer, colorectal cancer is the third most common cancer in the United States, with an estimated 384 individuals diagnosed each day. AICR estimates that 47 percent of US colorectal cancer cases can be prevented each year through modest lifestyle changes.
There are many possible mechanisms by which foods may act to reduce inflammation. Some kinds of dietary fiber, for example, promote healthy gut microbes. It is also important to remember that although inflammation appears important, there are other factors related to cancer risk, says Karen Collins, AICR’s Nutrition Advisor. “The goal is to take what we learn about inflammation and put it in context about what we know about eating and lifestyle choices that bring reproductive hormones, insulin and growth factors, and other influences in a cancer-protective direction.”
For now, we can confidently say that healthy eating — directly and through effects on healthy weight/body composition — act in multiple ways to reduce colorectal cancer risk.
JAMA Oncology study authors were funded by National Cancer Institute, National Institutes of Health, the Friends of the Dana-Farber Cancer Institute, the Nodal Award from the Dana-Farber Harvard Cancer Center, and a Stand Up To Cancer (SU2C) Colorectal Cancer Dream Team translational research grant.