Behind The Medical Headlines

Coffee is good for the liver

• Dr NC McAvoy, Clinical Research Fellow, Liver Unit, Royal Infirmary Of Edinburgh, Edinburgh, Scotland
• Dr PC Hayes, Professor of Hepatology, Liver Unit, Royal Infirmary Of Edinburgh, Edinburgh, Scotland

Summary

Considerable mainstream media attention focuses on lifestyle benefits of consuming different foods or beverages. While there is often little scientific evidence to support such reported benefits, Dr Norma McAvoy and Prof Peter Hayes review the evidence underpinning recent media coverage which was suggested that coffee consumption is good for the liver and is associated with a reduced risk of developing cirrhosis and liver cancer.

Declaration of interests: The authors have no interests to declare, other than one of us enjoys coffee!

Background

Earlier this year a paper in the Journal of Hepatology reported an inverse relationship between coffee drinking and hepatocellular carcinoma.¹ Whilst we are used to hearing short-lived claims linking food and disease, the relationship between coffee and liver disease seems reasonably evidence based.

Primary liver cancer or hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide, with approximately one million deaths per year. The incidence of HCC varies markedly geographically, and continues to rise, especially in the Far East and China where there is a high prevalence of Hepatitis B and C.

The most important risk factor for the development of HCC is the presence of liver cirrhosis, the most common causes of which are chronic hepatitis B and C infection, alcohol abuse, iron overload and obesity. As with most cancers, other environmental factors also play a significant role in HCC, including tobacco smoking, diabetes mellitus and obesity. HCC is associated with high mortality as the majority of patients have progressive/extensive disease at the time of clinical presentation. Several recent publications have identified an inverse association between coffee consumption and HCC as well as a beneficial influence on liver function and cirrhosis incidence.

Coffee and Liver Enzymes

Coffee drinking has an inverse relationship to gamma-glutamyl-transferase (GGT) production in the liver. The induction of GGT that occurs with alcohol is inhibited by coffee and thus may protect the liver against damage from alcohol excess. A study from Japan examined coffee consumption and serum GGT levels in 12,687 healthy volunteers. Increased coffee consumption was strongly and independently associated with decreased GGT activity amongst males (p <0·0001), especially amongst those with documented alcohol excess. In contrast, however, only a weak association between coffee intake and lower GGT levels was demonstrated in females in this study. A similar effect on the serum transaminases was also identified.

Another study reported on a cohort of 5,944 participants in the Third US National Health and Nutrition Examination Survey from 1988–1994 who had at least of one of the following: excess alcohol intake, obesity, viral hepatitis, iron overload or impaired glucose metabolism.² Increased serum ALT was found in 8·7 per cent and analysis showed that lower ALT levels were associated with higher coffee and caffeine intake. Comparing those in the highest caffeine quintile with those in the lowest the odds ratio was 0·31(95 per cent confidence interval 0·16–0·61). The effect of coffee and caffeine was seen across the different subgroups.

Coffee and Cirrhosis

Whilst coffee consumption might improve liver enzymes in at risk subjects, does it confer protection against cirrhosis? The answer to this is probably yes. There have been a number of studies identifying an inverse relationship between coffee consumption and cirrhosis. A Norwegian study looking at a 17-year follow-up of 5,130 adults who underwent screening for cardiovascular disease found less cirrhosis in coffee drinkers.³ It does appear there