Diets high in foods with potential to cause inflammation—including processed meat, red meat, fish and refined grains—are associated with an increased risk of developing colorectal cancer, according to a new study published in JAMA Oncology.

“Colorectal cancer is the third most commonly diagnosed cancer in both men and women in the United States,” wrote lead author Fred K. Tabung, MSPH, PhD, and colleagues. “Inflammation plays an important role in cancer development, including colorectal cancer. Though epidemiological studies have not consistently reported significant associations between prediagnosis levels of widely used inflammatory markers such as C-reactive protein, interleukin-6, and tumor necrosis factor alpha, and colorectal cancer risk, there is plausible evidence that inflammation plays an important role in colorectal cancer development.”

Researchers sought to examine if inflammatory diets increase colorectal cancer risk using an empirical dietary inflammation pattern (EDIP), created using a sample of 5,230 women in the Nurse’s Health Study (NHS) from 1984 to 2012. The EDIP is the weighted sum of 18 food groups which assesses minimum to maximum inflammatory diets. The lower scores are indicative of anti-inflammatory diets and high scores are those which indicate highly-inflammatory diets.

Food groups positively related to concentrations of inflammatory markers include processed meat, red meat, organ meat, fish, vegetables other than green leafy vegetables, refined grains, high-energy beverages (including carbonated drinks), low-energy beverages and tomatoes. Foods inversely related to concentrations of the inflammatory markers include beer, wine, tea, coffee, dark yellow vegetables, green leafy vegetables, snacks, fruit juice and pizza.

The researchers calculated the EDIP scores for each participant using a food frequency questionnaire which assessed dietary habits from eight four-year data cycles from the NHS and the Health Professionals Follow-up study. The final study cohort included more than 2,600 incident colorectal cases over a 2,571,831 person-years follow up.

Participants in the lowest fifth of the EDIP had a colorectal cancer rate of 113 men and 80 women compared to those in the highest fifth of the EDIP, who had a rate of 151 men and 92 women. This led to a difference of 38 and 12 more cases of colorectal cancer in men and women, respectively.

“Comparing participants in the highest versus the lowest EDIP quintile in multivariable-adjusted analyses, colorectal cancer risk was 44 percent higher in men, 22 percent higher in women and 32 percent higher in men and women combined,” the authors wrote.

Aside from a high inflammatory diet being a risk factor for developing colorectal cancer, the risk for developing colorectal cancer was higher among overweight or obese men (48 percent), lean women (31 percent), and men and women who did not consume alcohol (62 percent and 33 percent, respectively).

The researchers concluded that a change in dietary pattern among overweight or obese men, lean women, and men and women not consuming alcohol may benefit those populations and could possibly affect colorectal cancer development.