Hu Y, King M, Yuan C, et al. Association between coffee intake after diagnosis of colorectal cancer and reduced mortality. Gastroenterology. 2018;154(4):916-926.
Prospective observational study
To investigate the association between coffee intake after diagnosis of colorectal cancer (CRC) and mortality.
Participants (N=1,599) from the Nurses’ Health Study (1984-2012) and Professionals Follow-up Study (1986-2012) diagnosed with stage I or II CRC during the study period.
Semi-quantitative food frequency questionnaires (sFFQ) collected at least 6 months, but not more than 4 years, after diagnosis. Baseline, prediagnosis intake was surmised from the last sFFQ completed prior to diagnosis.
During a median 7.8 years of follow-up there were 803 total deaths, with 188 due to CRC. Participants who consumed at least 4 cups of coffee per day had a 52% lower risk of CRC-specific death compared to nondrinkers (hazard ratio[HR]:0.48; 95% confidence interval [CI]: 0.28-0.83; P for trend=0.003). Those who consumed more than 4 cups per day also had a 30% reduced risk of all-cause death (HR: 0.70; 95% CI: 0.54-0.91; P for trend<0.001). In assessing coffee intake before and after diagnosis, those who consistently consumed more than 2 cups per day before and after diagnosis had a 37% reduced risk of CRC-specific death (HR: 0.63; 95% CI: 0.44-0.89) and a 29% reduced risk of death from any cause (HR: 0.71; 95% CI: 0.60-0.85) vs those who consistently drank fewer than 2 cups daily.
In this study, consumption of coffee after diagnosis with CRC was associated with lower risk of CRC-specific mortality and overall mortality in a dose-dependent manner.
Of note, both caffeinated and decaffeinated coffee were associated with improved outcomes. This is in contrast with another recent study of stage III CRC patients that found significantly reduced risk of CRC-related death and overall death with consumption of caffeinated coffee only (>4 cups/day).1
Studies involving breast cancer have found associations between decaffeinated coffee and less cancer incidence or recurrence as well.2,3 Some of the other compounds possibly responsible for the apparent benefits of coffee include phenolic compounds (ie, chlorogenic acids), lipids (eg, kahweol, cafestol), polysaccharides (eg, galactomannans, acemannans), phytoestrogens (eg, trigonnelline), and countless other phytochemicals that directly affect the characteristic hallmarks of cancer.4
Panning back and assessing how coffee as a foodstuff may affect gastrointestinal function as a whole, its effects on the colonic microbiota and gut motility are possible mechanisms.5 In addition, coffee has been found to improve glucose control, and its net physiological benefits for those with metabolic syndrome or obesity have been proposed as possible mechanisms as well.1
As with all observational studies, associations may be a surrogate for other behaviors that lead to benefit. Lifestyle choices appear particularly well-proven to affect outcomes in colorectal cancer survivors.6 Based on this, there are many confounding surrogate lifestyle choices that are plausible for this study specifically. Perhaps those who drink more coffee are doing so in lieu of a sugary drink. Perhaps people who are highly anxious naturally opt to drink less coffee. Perhaps those who select not to drink coffee are more apt to be poor sleepers. Perhaps coffee drinkers exercise more, or are at least less sedentary, than non-drinkers. These surrogates can be summed up as excess energy balance, circadian disruption, and higher levels of endogenous catecholamines, all of which may affect outcomes. To be sure, we will not know if it is the coffee itself conferring benefit until there are interventional trials with randomized participants.
Despite this, lending a bit more credence to the hypothesis that coffee itself provides protection against CRC and its recurrence is the observation of a dose-response relationship, where higher intakes correlate with better outcomes.7 This is consistent with the larger pool of data on coffee, where overall mortality is lower in those who drink up to 5 cups daily, largely attributable to lower cardiovascular risk.8,9
Coffee is not just associated with less recurrence of CRC but with lower incidence of various cancers, implying it contains constituents with anticancer effects. Evidence is most consistent for the association of coffee intake with lower rates of initial diagnosis of colorectal, endometrial, and liver cancers.10-13 As metabolomics are used to decipher the role of genetic and microbiota influences on the metabolism of its constituents, we should gain better insight into precisely how coffee may confer benefits.14
Meanwhile, from a clinical standpoint, it is clear that coffee consumption does not need to be stopped in context of cancer prevention. If a patient enjoys coffee, then it is important we honor this ritual and let them know the data is on their side. For some patients, the guilt-free inclusion of what they thought was a vice may be therapeutic in itself.