There are multiple known risk factors for bladder cancer, such as smoking or the male gender. But the role of dietary factors like alcohol consumption is less clear. Urology experts try to gain more insight into the relationship between alcohol and bladder cancer with a systematic review and meta-analysis1, published in World Journal of Urology. Results show only an increased risk for heavy alcohol consumption in some subgroups. There appears to be no association when alcohol is consumed in moderation.
What is already known? A previous meta-analysis shows no association between moderate or heavy alcohol consumption and the risk of bladder cancer.2 However, the World Cancer Research Fund (WCRF) states that the evidence regarding the effect of alcohol on bladder cancer is limited and draws no conclusions.3
What does this study add? This meta-analysis includes more recent studies and performs additional subgroup analyses for gender, ethnicity, and type of alcoholic beverage.
The authors included 16 cohort and case-control studies in the meta-analysis. Nine of these studies looked at the association between moderate alcohol consumption and bladder cancer, resulting in more than 630.000 participants.
No increased risk with moderate alcohol consumption
At first, it appears that neither moderate (<30 grams alcohol per day) nor heavy alcohol consumption (>30 to 150 grams alcohol a day) is associated with the risk of bladder cancer. With all the sub-group analyses the authors performed, this association did indeed not change for moderate alcohol consumption.
Heavy alcohol consumption
However, this was not the case for heavy alcohol consumption. For example, when the authors looked at different ethnic groups, it turns out that Japanese do have increased risk to develop bladder cancer with heavy alcohol consumption, increasing the risk with 31% in comparison to non-drinkers. This can most likely be explained by the fact that Japanese have a higher chance to have a mutation in a specific gene, which impairs them to breakdown alcohol.
Also, when looking at the difference between gender and type of drink, it appears that men with a heavy consumption of spirits have an increased risk of 42%.
A possible explanation the authors give why heavy alcohol consumption could play a role in developing bladder cancer is due to the intermediate breakdown product of alcohol, acetaldehyde. A proportion of this metabolite, which is classified as carcinogenic, is excreted through the urinary tract. However, the authors say, the kidneys and bladder are not exposed to acetaldehyde that much as you have to go to the toilet more often when drinking alcohol.
– Systematic analysis
– Subgroup analyses performed
– Definition of amount of alcohol per day (moderate/heavy) differs per study
– Only observational studies
– Analysis not adjusted for sick-quitters
1. Vartolomei, M. D., Iwata, T., Roth, B., Kimura, S., Mathieu, R., Ferro, M., … & Seitz, C. (2019). Impact of alcohol consumption on the risk of developing bladder cancer: a systematic review and meta-analysis. World journal of urology, 1-12.
2. Pelucchi, C., Galeone, C., Tramacere, I., Bagnardi, V., Negri, E., Islami, F., … & La Vecchia, C. (2011). Alcohol drinking and bladder cancer risk: a meta-analysis. Annals of oncology, 23(6), 1586-1593.
3. WCRF (2015) Diet, nutrition, physical activity and bladder cancer. Revised 2018.
Photocredits: ‘doctor’ from DarkoStojanovic