Coffee consumption and liver function

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Coffee and Health includes current scientific information on a wide range of coffee-related topics. One such topic addresses coffee consumption and liver function. This post provides an overview of this topic.

Liver disease is estimated to affect 6% of the EU’s population. There are several different types of liver disease including hepatitis, alcohol-related diseases, fatty liver disease and cancer. Of these, liver cancer is the third most common cause of cancer-related deaths globally and is the leading cause of death amongst patients with liver cirrhosis. Throughout Europe, alcohol remains the most important cause of liver disease, responsible for over 70% of all deaths.

Many liver diseases cause scar tissue, known as fibrosis, to develop. In the early stages of fibrosis, the liver functions relatively well and few people experience symptoms. But as the inflammation and liver injury continue, scar tissue builds up. This can eventually disrupt the metabolic functions of the liver and lead to cirrhosis in which the liver is severely scarred, its blood flow restricted and its ability to function severely impaired.

Regular coffee consumption may decrease the risk of liver cancer
An increased consumption of coffee may help to reduce the risk of liver cancer. Two reviews of a total of ten studies have found that as coffee consumption increases, risk of liver cancer decreases. This association is seen in healthy individuals as well as those with previous liver disease. The two remarkable features of the results of these studies are their consistency and the very large reduction in observed disease risk.

Overall, an increase in coffee consumption of two cups per day, in individuals who typically consume anything from one to over five cups a day, is associated with a 43% lower risk of developing liver cancer.

Coffee may decrease the rate at which fibrosis progresses
Coffee drinking has also been related to a reduced risk of other liver diseases, hence suggesting a continuum of favourable effects of coffee on liver function.

One review concluded that patients with higher coffee consumption displayed a slower progression of fibrosis, especially those with alcoholic liver disease. Any slowing down in fibrosis development prolongs the function of the liver, delaying the progression to cirrhosis and irreparable liver damage.

Four recent patient studies have also all found that those patients who drank more coffee tended to have less severe fibrosis or a slower progression of fibrosis than those who drank less coffee. This effect was seen in patients with hepatic fibrosis, cirrhosis, non-alcoholic fatty liver disease and Hepatitis-C related liver disease.

Although studies of liver disease in patients have had promising results, there are limitations to patient studies which must be considered. Small subject numbers and ongoing patient therapy can interfere with trials. If patients change their habits or diet as a result of their disease or its standard therapy, this can also bias results.

Potential mechanisms
There is evidence of quite a large positive effect of coffee consumption on liver cancer. Studies to date also suggest beneficial effects on liver fibrosis and alcoholic cirrhosis. Several potential mechanisms, which may be responsible for these effects, are currently under investigation.

The role of caffeine
There is some evidence for a potential role for caffeine on liver cancer. Studies have shown that caffeine and, in particular, its main metabolite paraxanthine, can suppress the synthesis of CTGF (connective tissue growth factor) which may slow down the progression of liver fibrosis, alcoholic cirrhosis and liver cancer.
Some of the studies however do not find an association with tea, suggesting that the mechanism of action may not be dependent solely on caffeine.

Possible roles for other coffee constituents
Other compounds present in coffee are also being studied. Two naturally occurring coffee compounds, kahweol and cafestol, both oil components in coffee, are believed to have anti-carcinogenic properties which could be responsible for a reduction in the risk of liver cancer.

Also present in coffee, two plant phenols, chlorogenic and caffeic acids have been found to have anti-viral properties and to be capable of preventing replication of the Hepatitis B virus. This could also have a potential role in coffee’s effects on the liver.

In conclusion, evidence suggests that moderate coffee consumption is related to a lower risk of liver cancer and slowing of disease progression in liver fibrosis and alcoholic cirrhosis. There is also evidence that moderate coffee drinking could be beneficial in slowing the progression of viral infections of the liver. Several mechanisms underlying these effects are currently under investigation.

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