Regular coffee consumption is inversely correlated to colorectal cancer risk, according to results of a study published in the April issue of Cancer Epidemiology, Biomarkers & Prevention.
Coffee has been proposed as a protective agent against colorectal cancer because several of its components affect the physiology of the colon. These compounds include caffeine, melanoidins, diterpenes, and polyphenols. Protection may arise from changes to the microbiome, antioxidant effects, antimutagenic effects, reduction of bile acid secretion, and improved bowel functions such as motility and capacity.
To substantiate widespread claims of the protective effect of coffee, Stephanie L. Schmit, PhD, MPH, from the USC Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, and colleagues administered a validated, semiquantitative food frequency questionnaire to 5145 cases and 4097 controls from the Molecular Epidemiology of Colorectal Cancer (MECC) study, a population-based investigation in northern Israel. The researchers considered coffee type (caffeinated or decaffeinated, boiled black coffee, black espresso, instant coffee, and filtered coffee), cancer site (colon and rectum), and ethnic subgroup (Ashkenazi Jews [61.3% of the population], Sephardi Jews [21.4%], and Arabs [13.5%]). The study adjusted for daily total liquid and caloric consumption.
Overall coffee consumption was associated with 26% lower odds of developing colorectal cancer (odds ratio [OR], drinkers vs nondrinkers, 0.74; 95% confidence interval [CI], 0.64 - 0.86; P < .001).
The results also indicated an inverse association for boiled coffee (OR, 0.82; 95% CI, 0.71 - 0.94; P = .004) and decaffeinated coffee (OR, 0.82; 95% CI, 0.68 - 0.99; P = .04). Factoring in total daily liquid consumption yielded similar findings (OR, 0.80; 95% CI, 0.68 - 0.93; P = .005), as did total calorie consumption (OR, 0.74; 95% CI, 0.63 - 0.86; P < .001).
Higher coffee consumption was associated with lower odds of developing colorectal cancer: one to less than two daily servings (OR, 0.78; 95% CI, 0.68 - 0.90; P < .001), from 2 to 2.5 daily servings (OR, 0.59; 95% CI, 0.51 - 0.68; P < .001), and more than 2.5 daily servings (OR, 0.46; 95% CI, 0.39 - 0.54; P < .001). The dose–response relationships were statistically significant for cancers of the colon and rectum and for Ashkenazi Jews and Sephardi Jews.
Arabs reported the highest total amount of coffee drinking (average 3.3 servings per day), followed by Sephardi Jews (2.1 servings per day) and Ashkenazi Jews (1.8 servings per day).
Cases compared with controls were slightly younger and less likely to take statins or low-dose aspirin, to smoke, to be physically active, and to eat five or more servings of vegetables per day. Cases also reported a stronger family history of colorectal cancer. The research group previously published a study identifying six susceptibility genetic loci for colorectal cancer.
The new findings apply to lower daily coffee consumption than previous investigations. Other studies have correlated coffee consumption with decreased risk for colon cancer recurrence, and a meta-analysis previously associated coffee consumption with lowered colorectal cancer risk.
Limitations of the study include reliance of recall of coffee consumption going back 1 year, lack of standardization of serving sizes, and possible effects of avoidance of coffee by individuals with gastrointestinal diseases.
The researchers have disclosed no relevant financial relationships.
Cancer Epidemiol Biomarkers Prev. 2016;25:634-639