A proinflammatory diet replete in red, processed, and organ meat, among other foods, increases the risk for colorectal cancer (CRC) in both men and women. It is especially risky in overweight and obese men, and, paradoxically, also in lean women.
The finding comes from a study published online January 18 in JAMA Oncology.
“There were two major findings from this study,” Fred Tabung, MSPH, PhD, Harvard T. H. Chan School of Public Health, Boston, Massachusetts, said in an interview with JAMA Oncology.
“The first was that higher dietary inflammatory potential was associated with an increased risk of developing colorectal cancer in both men and women, and the second was that the risk of developing colorectal cancer was even higher amongst overweight and obese men and in lean women and among men and women not consuming alcoholic beverages,” he added.
“So dietary recommendations for both men and women would be to consume a dietary pattern with a low potential to contribute to inflammation in the colon and that pattern would be high in green leafy vegetables, dark yellow vegetables, coffee, and tea and low in processed meat, red meat, refined grains, and sugar-sweetened beverages,” Dr Tabung said.
Details of the Study
For the study, Dr Tabung and colleagues used data from the Health Professionals Follow-up Study and the Nurses’ Health Study to track the development of colorectal cancer in a total of 121,050 adults over 26 years of follow-up.
“Every 4 years, participants received validated semiquantitative food frequency questionnaires (FFQ) for dietary assessments,” the investigators explain.
The team rated 18 food groups for their inflammatory potential using an empirical dietary inflammatory pattern (EDIP) score based on circulating levels of three inflammatory biomarkers — interleukin-6, C-reactive protein, and tumor necrosis factor–alpha receptor 2.
Diets were rated on a continuum from a maximally anti-inflammatory diet to a maximally proinflammatory diet ― the higher the EDIP score, the more proinflammatory the diet.
Foods that were positively related to concentrations of these inflammatory markers included tomatoes; both high- and low-energy carbonated beverages; vegetables other than green leafy and dark yellow vegetables; and processed meat, red meat, organ meat, and fish other than dark-meat fish.
In contrast, beer, wine, tea, coffee, dark yellow and green leafy vegetables, snacks, fruit juice, and pizza were inversely related to concentrations of the same inflammatory markers.
Over long-term follow-up, there were 2699 cases of colorectal cancer across the two cohorts.
“Comparing participants in the highest vs the lowest EDIP quintile in multivariable-adjusted analyses, colorectal cancer risk was 44% higher in men (HR [hazard ratio], 1.44; 95% CI [confidence interval], 1.19 – 1.74; P < .001 for trend), 22% higher in women (HR, 1.22; 95% CI, 1.02 – 1.45; P = .007 for trend), and 32% higher in men and women combined (pooled HR, 1.32; 95% CI, 1.12 – 1.55; P < .001 for trend),” the study authors report.
The association between the highest EDIP quintile and increased colorectal cancer risk was observed for all anatomic sites with the exception of the rectum in women, in which the risk for rectal cancer was not higher among women with the highest EDIP scores compared to those with the lowest, they add.
The risk of developing colorectal cancer was 48% higher among overweight or obese men with the most proinflammatory diets compared to those with the least inflammatory diets (P = .004).
Interestingly, the risk for colorectal cancer was 31% higher for lean women in the highest EDIP quintile compared to those in the lowest quartile (P = .01).
Alcohol and CRC Risk
Consumption of alcohol also affected colorectal cancer risk, but in a somewhat paradoxical manner, and also in contrast to previous findings.
Whereas previous studies have shown that alcohol consumption is associated with an inreased risk of developing cancer, in this study, the risk for colorectal cancer appeared to be decreased in those who drank.
For example, men in the highest EDIP quintile who did not drink alcohol were 62% more likely to develop colorectal cancer over the 26-year follow-up compared to men in the lowest quintile (P = .002). Women with the highest proinflammatory diets who did not drink alcohol were 33% more likely to develop colorectal cancer compared to women with the least inflammatory diets (P = .03).
Men in the highest EDIP quintile who reported drinking more than one alcoholic beverage a day still had a 23% higher risk for colorectal cancer compared to those in the least inflammatory diets, but women in the highest quintile who consumed more than one drink a day had a 13% lower risk for colorectal cancer than those with the least inflammatory diets (P = .34).
The study authors observe that high levels of alcohol consumption have been associated with a higher cancer risk, so it may be that the pathway through which alcohol increases the risk for cancer occurs through mechanisms other than its effect on inflammation.
Study Adds to Information
“I think the study adds a great deal of information both in terms of the biology [of colorectal cancer] as well as opportunities to reduce the risk,” coinvestigator Charles Fuchs, MD, MPH, Yale Cancer Center, New Haven, Connecticut, said in the same JAMA Oncology interview.
For example, multiple studies have affirmed that aspirin reduces the risk for colorectal cancer, at least in part through inhibition of inflammation, he observed.
“What I think this study documents is that there are diets that can similarly affect your state of inflammation, and those diets may affect risk independent of aspirin,” Dr Fuchs noted.
We can modify our states of inflammation through our diet and lifestyle.
“So in terms of a risk pattern, I think this study is helpful, and it adds to the growing body of evidence that inflammation is important and that we can modify our states of inflammation through our diet and lifestyle,” as he suggested.
Dr Fuchs cautioned that patients who are at high risk for colorectal cancer either because of a family history or their own history with respect to risk factors, such as having polyps, need to discuss other interventions, including the use of aspirin and possibly more frequent colonoscopies than are generally recommended above and beyond adhering to dietary precautions alone.
The study was supported by grants from the National Cancer Institute, the National Institutes of Health, and Stand Up To Cancer and by the Friends of the Dana-Farber Cancer Institute and the Dana-Farber Harvard Cancer Center. The authors have disclosed no relevant financial relationships.
JAMA Oncol. Published online January 18, 2018. Full text
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