Coffee consumption and risk of colorectal cancer: A systematic review and meta‐analysis of prospective cohort studies

Abstract

An inverse association between coffee consumption and the risk of colorectal cancer has been found in several case-control studies, but such an association was not consistent in prospective cohort studies. We conducted a systematic meta-analysis of prospective cohort studies on coffee consumption and colorectal cancer published up to June 2008. We combined relative risks (RR) for colorectal cancer comparing high vs. low categories of coffee consumption using random-effects models. We identified 12 eligible cohort studies, which included 646,848 participants and 5,403 cases for colorectal cancer. The summarized result of the meta-analysis comparing high-vs. low-consumption categories showed no significant effect of coffee consumption on colorectal cancer risk (RR 5 0.91; 95% confidence intervals [CI]: 0.81-1.02). The RR was 0.93 (95% CI: 0.71-1.22) when considering 4 studies conducted in the United States of America, 0.91 (95% CI: 0.76-1.10) for 5 studies from Europe, and 0.83 (95% CI: 0.62-1.10) for 3 Japanese studies. No significant differences by sex and cancer-site were found, but there was a slight suggestion of an inverse association between coffee consumption and colon cancer in women (RR 5 0.79; 95% CI: 0.60-1.04), especially Japanese women (RR 5 0.62; 95% CI: 0.37-1.05). The suggestive inverse associations were slightly stronger in studies that controlled for smoking and alcohol, and in studies with shorter follow-up times. Information on coffee type, its serving size, or brewing method may provide a better understanding of this reassuring result and the real role of coffee on colorectal cancer risk. ' 2008 Wiley-Liss, Inc.Key words: caffeine; coffee; colorectal neoplasms; meta-analysis; prospective studies Colorectal cancer is the third most common cancer worldwide. 1 Although obesity, smoking, alcohol, and physical inactivity are important risk factors for colorectal cancer, nutritional factors are also considered to play an important role for its development. 2 The relationship between coffee consumption and colorectal cancer risk has been extensively examined over the last 4 decades. 3 Coffee is a complex mixture of more than a thousand chemicals, and these constituents have potential genotoxic and mutagenic properties, but also antioxidant and antimutagenic activities, 4,5 any of which could affect colorectal cancer risk. Several case-control studies have shown an inverse association between coffee consumption and risk of colorectal cancer. A meta-analysis, combining the results of 12 case-control studies, found an odds ratio of 0.72 (95% confidence interval [CI]: 0.61-0.84) for high vs. low coffee intake, but the combination of 5 cohort studies demonstrated no association (relative risk [RR] 5 0.97; 95% CI: 0.73-1.29). 6 Although the data from case-control studies are relatively consistent, they may be subject to recall bias with respect to coffee consumption and selection bias with respect to the control group. Additional prospective cohort studies excluding those biases would be more useful to s...

Coffee consumption and risk of colorectal cancer: a meta-analysis of observational studies

“…However, there was a slight suggestion of an inverse association between coffee consumption and colorectal cancer (RR 5 0?94, 95 % CI 0?88, 1?01; P for heterogeneity 5 0?85; I 2 5 0 %; . For duration of follow-up, we applied 10 years of follow-up as a cut-off because the mean of follow-up time for all sixteen cohort studies was roughly 10?5 years (6) and there were nine and seven studies whose follow-up periods were over and less than 10 years, respectively. Results of analyses in stratum of follow-up period indicated that studies with shorter followup time (,10 years) tended to show marginally inverse relationships between coffee intake and the risks of colorectal (RR 5 0?92, 95 % CI 0?85, 1?01) and colon caner (RR 5 0?90, 95 % CI 0?81, 1?00; Table 2).…”

“…However, there was a slight suggestion of an inverse association between coffee consumption and colon cancer in women (RR 5 0?79; 95 % CI 0?60, 1?04) (6) . Our findings confirmed these previous results.…”

“…Several studies have reported that coffee consumption tends to be strongly associated with smoking, alcohol and physical inactivity, which may attenuate the association of coffee with colorectal cancer (4)(5)(6)34,37) . In the current meta-analysis there were three case-control (11,44,46) and seven cohort studies (22)(23)(24)(25)27,32,52) providing risk estimates adjusted for smoking status, alcohol intake and physical activity.…”

Coffee reduces KRAS expression in Caco-2 human colon carcinoma cells via regulation of miRNAs

“…Multiple epidemiological studies have demonstrated an inverse association between coffee consumption and risk of colorectal cancer (4)(5)(6). However, the molecular basis of this effect remains to be fully understood (7).…”

Insulin resistance and cancer: epidemiological evidence

“…Table 1), while a borderline protective effect was also shown for colon cancer. This effect was stronger in women (RRZ0.79) than in men (RRZ1.00), particularly in Japanese populations (RRZ0.62), although a plausible explanation for this sex difference deserves further investigation (Je et al 2009). A recently large-scale prospective study in the US reported a null association for total cancer mortality (Freedman et al 2012), which suggests that the effect of coffee varies by cancer site, likely depending on whether it is associated with insulin resistance or not.…”