Coffee and bladder cancer
Studies provided sufficient evidence for the Institute of Cancer Research (IARC), which concluded that there is inadequate evidence of an association between coffee intake and bladder cancer, highlighting that smoking may have confounded results in some of the early studies1.
Additionally, the World Cancer Research Fund (WCRF) 2018 Bladder Cancer Report lists coffee under ‘limited evidence - no conclusion’42. Some work has also suggested variable results in an Asian population and in male coffee drinkers, so further research is clearly required.
- A 2017 study following 73,346 Japanese individuals, where 274 cases of bladder cancer were identified, concluded that the data indicates a significant inverse association between coffee consumption and bladder cancer43
- A 2020 analysis of 12 cohort studies in Japan concluded that an increased risk of bladder cancer was seen among coffee drinkers in male smokers, but not those who had never smoked, or in females. The authors suggested that the results were unlikely to be causal and were possibly caused by residual confounding of smoking44
Research investigating 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 required45
- A 2020 dose response analysis suggested the risk of bladder cancer increased with each with each additional cup of coffee (125 ml) of coffee (RR1.07 for an additional cup). However, the authors suggested that the inconsistent results between sexes and the absence of an association in never smokers, indicates that the associations are possibly caused by residual confounding of smoking44
Coffee and kidney cancer
Research consistently suggests there is no conclusivelink between coffee consumption and kidney cancer46. During the last three decades, the incidence of kidney cancer has constantly increased, leading to the search for possible links with diet. The WCRF 2018 Kidney Cancer Reportlists coffee under ‘Limited Evidence – No Conclusion’47 and the 2016 IARC Report concluded that there is inadequate evidence to suggest any association between coffee consumption and kidney cancer1.
- A 2017 meta-analysis of 22 observational studies (16 case-control and 6 cohort studies) concluded that there was no significant association between coffee consumption and renal cell carcinoma46. The authors advised that a potential role in reducing the risk of renal cell carcinoma, particularly in men, requires further investigations
Coffee and prostate cancer
Research suggests that coffee consumption is not associated with an increased risk of prostate cancer48-50, with a number of studies suggesting a reduced risk of the disease. The WCRF 2018 Prostate Cancer Report lists coffee under ‘limited evidence - no conclusion’51. Additionally, IARC’s 2016 review concluded that research consistently suggests no association between coffee consumption and risk of prostate cancer1.
- A 2021 systematic review and meta-analysis suggested that a higher intake of coffee may be associated with a lower risk of prostate cancer. The authors concluded that compared with the lowest coffee intake category, there was a 9% reduction in the risk of prostate cancer for the highest category50
