Coffee consumption and bladder, kidney and prostate cancers

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Coffee and bladder cancer

Early, limited research had suggested a potential association between coffee and bladder cancer. However, more recent studies have provided sufficient evidence for IARC to conclude that there is inadequate evidence of such an association, highlighting that smoking may have confounded results in some studies.

  • In 1991, the International Agency for Research on Cancer (IARC) considered, based on the limited evidence available at that time, that coffee drinking was possibly carcinogenic to the human urinary bladder. It classified coffee in Group 2B (possibly carcinogenic to humans)4.
  • Seven meta-analyses have reviewed the associations between coffee consumption and bladder cancer risk, presenting variable results55-61. Based on current evidence it is difficult to draw firm conclusions about associations between coffee consumption and bladder cancer risk.
  • Some papers report an increased risk of bladder cancer55,61 including a 2001 meta-analysis, which concluded that coffee consumption increased the risk of urinary tract cancer by 20%56. However, other analyses report no convincing evidence of an association57-61. A 2016 study, following 73346 Japanese individuals where 274 cases of bladder cancer were identified, concluded that the data indicates a significant inverse association between coffee consumption and bladder cancer62.
  • A number of confounding factors have been reported, including smoking, maleness and Asian origin. Three meta-analyses suggest that compared with smokers, non-smokers appear to have a slightly increased risk of bladder cancer55,60,61, although a 2016 Japanese study concluded that an inverse association between coffee consumption and bladder cancer was observed even when stratified for smoking status62. Further data suggests that coffee consumption is associated with a decreased risk of bladder cancer in Asian people60. Some research also suggests an increased risk of bladder cancer in male coffee drinkers61,63. Further work is required to understand these associations in more detail.
  • Evidence for a dose response relationship between coffee intake and bladder cancer is also limited. A 2014 meta-analysis found no association between coffee consumption and bladder cancer, but since the authors reported insignificant associations in analysis of intakes (highest vs. none/lowest) and in dose response analyses, further research is again required59.
  • The WCRF 2015 Bladder Cancer Report lists coffee under ‘Limited Evidence – No Conclusion’64.
  • IARC’s 2016 review found no clear association between coffee intake and cancer at any body site, including the bladder. Residual confounding factors, particularly smoking, were highlighted as factors that may have distorted results in some earlier bladder cancer studies5.

Coffee and kidney cancer

Research consistently suggests there is no link between coffee consumption and kidney cancer.

  • During the last three decades, the incidence of kidney cancer has constantly increased, leading to the search for possible links with diet. The etiology of kidney cancer suggests an increased risk with smoking and being overweight, while fruits and vegetables appear to be protective.
  • The World Cancer Research Fund (WCRF) identified 18 case-control and 5 cohort studies clearly and consistently indicating the lack of a link between coffee consumption and kidney cancer8.
  • A few additional studies reviewed, including a synthesis of 13 prospective studies including 530,469 women, 244,483 men and 1,478 cases of kidney cancer, did not find an association between coffee consumption and kidney cancer (relative risk 0.99 – mean for all studies)65,66, and a 2014 meta-analysis also found no association59.
  • The WCRF 2015 Kidney Cancer Report lists coffee under ‘Limited Evidence – No Conclusion’67.
  • In 2016, IARC concluded that there is inadequate evidence to suggest any association between coffee consumption and kidney cancer5. 

Coffee and prostate cancer

ISICS cancer topic graphics V57

Research suggests that coffee consumption is not associated with an increased risk of prostate cancer.

  • A meta-analysis of 6 cohort and 5 case-control studies found no influence of coffee consumption on the risk of developing prostate cancer68. Coffee consumption cumulated over the entire lifespan, age of onset and duration had no effect on the incidence of prostate cancer.
  • However, a 2011 meta-analysis found that coffee drinkers had a 21% lower risk of developing prostate cancer than non-coffee drinkers (relative risk 0.79)9.
  • A prospective analysis of 47,911 men in the Health Professionals Follow-up Study, 5,035 of which had prostate cancer, observed a strong inverse association between coffee consumption and risk of advanced prostate cancer. Men who consumed 6 or more cups of coffee per day had a 60% lower risk of lethal and advanced prostate cancer than non-drinkers. The association appeared to be related to the non-caffeine components of coffee, as the association with lethal cancer was similar for regular and decaffeinated coffee69.
  • A 2014 meta-analysis suggested that coffee consumption has a protective effect on prostate cancer, concluding that coffee consumption may be inversely associated with the risk of fatal prostate cancer, but showed no clear evidence of an association with its incidence70.
  • Three further meta-analyses published in 2014 also supported the hypothesis that coffee consumption may decrease the risk of prostate cancer71-73. One suggested a significant inverse relationship for fatal prostate cancers and high-grade prostate cancers71, whilst a second suggested that intakes of coffee greater than 4 or 5 cups per day may be associated with a reduced risk of overall prostate cancer, as well as fatal and high-grade prostate cancers72.
  • A 2015 meta-analysis concluded that coffee consumption may be associated with a reduced risk of prostate cancer, particularly amongst European populations, and observed an inverse association with non-advanced prostate cancer74.
  • The WCRF 2015 Prostate Cancer Report lists coffee under ‘Limited Evidence – No Conclusion’75.
  • IARC’s 2016 review concluded that research consistently suggests no association between coffee consumption and risk of prostate cancer5.

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