Coffee & Cancer Risk

Latest Headlines: ‘Drinking coffee may help prevent liver cancer’ 

Coffee & liver cancer3In the news this week from The Guardian, Daily Mail, Independent & Daily Express has been headlines regarding drinking coffee to reduce your risk of cancer.  I have reviewed the journal behind the headlines to find out the facts:

The journal was a meta-analysis and a systematic review.  This means a large range of studies were reviewed and statistically analysed to form a conclusion of the findings.  The quality of this type of study is dependent on the quality of the studies available that are analysed.

What the study found:

The study found that drinking an extra cup of coffee per day was associated with a 20 % reduction in the risk of developing hepatocellular cancer (HCC).  In addition, it found that drinking two extra cups was linked with a 35 % reduction, and up to five cups halved the risk.  Decaffeinated coffee was also found to have a beneficial effect, although the results were not as strong. 

Study strengths

  • The meta-analysis reviewed a body of evidence already associating coffee consumption with a positive effect on liver diseases
  • The first meta-analysis to look at number of coffee drinks per day
  • A large number of participants analysed within the meta-analysis

 Study weaknesses

  • Most of the studies reviewed within the meta-analysis were observational. This means the studies would have been susceptible to bias, missing data and confounding data, which means the quality of the studies were reduced, impacting on the results of the meta-analysis.
  • Many of the studies reviewed had not taken into consideration BMI, type 2 diabetes and viral hepatitis status. Alcohol may not always have been reported accurately within the patient group – taking into account alcohol dependency.
  • Bias as a result of the different types of measurements and preparations of coffee.
  • Lack of data of high coffee intakes (> 5 cups/day)

 Important points to keep in mind

The type of liver cancer being investigated (HCC) accounts for 85-90% of cases and most commonly develops as a results of cirrhosis due to chronic viral hepatitis B or hepatitis C, excessive alcohol consumption or as a result of non-alcoholic fatty liver disease.  Therefore, the most important way to reduce your risk of developing liver cancer is to reduce the amount of alcohol drunk, avoiding the risks of viral hepatitis, eating a healthy balanced diet and performing regular physical activity.

No randomised control trials (RCTs) have been performed investigating coffee consumption and preventing liver disease, which would provide stronger evidence.  With this in mind it is worth noting in many instances RCTs have shown an opposite effect to the vast amount of observational studies.  Until these are completed we will not know.

Despite the study finding that coffee was protective against liver cancer, the quality of the evidence reviewed was low.

High intakes of caffeine and coffee potentially can cause harm.  There have been studies to show coffee can increase the risk of lung cancer, bone fractures and worsen cholesterol and therefore increase cardiovascular disease (CVD) risk. There are also groups of people who should avoid this level of caffeine (e.g. during pregnancy).

In Summary

The results of this meta-analysis suggest drinking coffee (up to 5/day) could have a significant effect on your liver cancer risk.  If you have chronic liver disease, this might be something you want to consider.  If you already drink coffee this could potentially be a benefit.  If you do not drink coffee and do not have any liver problems, there is not enough evidence to recommend starting the consumption of coffee.

 

Reference
Kennedy OJ, Roderick P, Buchanan R, et al. Coffee, including caffeinated and decaffeinated coffee, and the risk of hepatocellular carcinoma: a systematic review and dose–response meta-analysis. BMJ Open 2017;7:e013739. doi:10.1136/ bmjopen-2016-013739
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