Coffee consumption and bladder, kidney and prostate cancers
Coffee and bladder cancer
The evidence for a relationship between coffee consumption and bladder cancer is inconclusive.
Tobacco and exposure to aromatic amines are the two main risk factors for bladder cancer. However, factors linked to lifestyle are also involved.
- In 1990, the International Agency for Research on Cancer (IARC) considered that there was limited evidence available at that time that coffee drinking was carcinogenic to the human urinary bladder. It classified coffee in Group 2B (possibly carcinogenic to humans).
- Since then, four out of six cohort, and 29 out of 37 case-control studies, have reported a moderate increase in the risk of bladder cancer with coffee consumption4. However, this increased risk is related neither to the amount of coffee consumed, nor to the exposure duration, which suggests of a non-causal association.
- A number of recent studies and meta-analyses report up to 18% higher risk of bladder cancer (relative risk 1.0-1.18) in coffee drinkers, no association in women, and an increased risk of 26% in men4,6,26. However a critical confounding factor is linked to the type of water used to prepare coffee. Indeed, chlorinated tap water can increase the risk of bladder cancer, whereas mineral water does not. This could be critical, particularly in the last stages of the disease, since patients tend to significantly increase their fluid intake at that time.
- This apparently increased risk of bladder cancer with coffee consumption may be attributed to residual confounding by smoking, which usually directly correlates with both alcohol and coffee consumption, or to an association between alcohol, coffee and a yet unidentified risk factor26.
- However, a more recent meta-analysis of prospective cohort studies, of which 9 studies looked at bladder cancer, found that coffee consumption was inversely associated with bladder cancer in men, whereas the trend was not seen in women7.
Coffee and kidney cancer
Research 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 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 cancer6.
- 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, confirmed the lack of a link between coffee consumption and kidney cancer across all studies reviewed (relative risk 0.99 – mean for all studies)27, 28.
Coffee and prostate cancer
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 cancer29. Coffee consumption cumulated over the entire lifespan, age of onset and duration had no effect on the incidence of prostate cancer.
- However, a recent meta-analysis found that coffee drinkers had a 21% lower risk of developing prostate cancer than non-coffee drinkers (relative risk 0.79)7.
- 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 six 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 coffee30.