A study in today’s JAMA Oncology links diets that include foods that can cause inflammation to an increased risk of colorectal cancer. Those foods include meats, refined grains, and high-calorie beverages. We asked Marji McCullough, SCD, RD, strategic director of nutritional epidemiology at the ACS.
“There has been a lot of interest in the role of diet in inflammation, and in fact several anti-inflammatory diets have begun to be promoted. This is an observational study, not interventional, so it has some limitations, but it does shed some light on the issue.
“There are several ways diet may influence colorectal cancer risk, including inhibiting or promoting inflammation, which is the focus of this paper. Chronic inflammation can cause DNA damage and lead to unregulated cell growth. Other ways diet could influence colorectal cancer risk is through antioxidant effects (protecting against DNA damage), influencing the cell cycle, and direct consumption of carcinogens.
“While it’s tempting to focus on specific foods, how overall diet contributes to this inflammatory effect is likely more important than individual foods because foods may act together in influencing disease risk.
“It’s possible the impact of diet is even greater than that measured in the current study, which captured only some of the foods that are likely to influence inflammation. For example, certain spices and food preparation methods that were not included may have strong effects on inflammation.
“It’s interesting to consider that what you eat may be just as important as what you don’t. In other words, many foods and beverages are substitutions for each other. One strength of this paper is that it takes the total diet into account.
“Another important aspect of this study is that it focused on foods, not supplements. It underscores how food can have significant roles in influencing disease risk.
“As far as what people should know about colorectal cancer and diet: The International Agency for Research on Cancer (IARC) determined that processed meat is a carcinogen, and red meat is a probable carcinogen, so lower intakes of both would reduce colorectal cancer risk. Whole grains and (low fat) dairy foods are associated with lower risk of colorectal cancer. Whole grains add bulk to the diet and may dilute carcinogens. Whole grains and other plant foods also contribute to beneficial microbiome diversity. Dairy foods contain calcium and vitamin D, which have beneficial effects on cell proliferation and differentiation.
“The bottom line: It’s important to consider the total diet, as a combination of lots of healthy foods and lower amounts of unhealthy foods are likely to have additive and synergistic effects on lowering cancer risk.”