Coffee consumption and liver function

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Coffee and risk of liver cancer

In 2016, the International Agency for Research on Cancer (IARC) published an updated review of the scientific evidence related to coffee and cancer, finding no conclusive evidence for a carcinogenic effect of coffee overall, and, concluding that the research suggests an inverse association between coffee consumption and liver cancer9.

Three meta-analyses of both prospective cohort and case control studies looking at liver cancer, concluded that all ten reviewed epidemiological studies show an inverse association between coffee consumption and liver cancer10-12. The findings suggest that an increased consumption of coffee may reduce the risk of liver cancer.

The inverse association between coffee consumption and liver cancer exists both in participants with and without a history of liver disease. Overall, an increase in consumption of 2 cups of coffee per day is associated with a 43% reduced risk of liver cancer amongst populations who typically consume anything from 1 to over 5 cups per day.

The two striking features of the results of these epidemiological studies are their consistency and the very large reductions in observed disease risk.

The results of the cohort studies included in the meta-analyses indicate a dose-response relationship between frequency of coffee consumption and the reduced risk for liver cancer. For the case-control studies, the same holds to a lesser extent. However, it should also be noted that most of the included studies originate from one country, namely Japan.

In 2011, a further case-control study conducted in a Chinese population of hepatitis C chronic carriers found that moderate coffee consumption reduced the risk of hepatocellular carcinoma by almost half with a significant dose-response effect, reducing the risk for moderate coffee drinkers by 59%13.

A case-control study with a group of hepatocellular carcinoma (HCC) patients suggested that a lifetime coffee consumption greater than 20,000 cups (or an average of 3 per day) was negatively associated with development of this cancer. This association did not affect the risk of HCC in hepatitis B patients14.

Research in a group of Finnish male smokers suggested that coffee intake was inversely associated with incident liver cancer and mortality from chronic liver disease, irrespective of whether the coffee was boiled or filtered15.

Data from the US Multi Ethnic Cohort also suggests that coffee consumption is inversely related to the incidence of hepatocellular cancer, showing a risk reduction of 38% in those who drank 2-3 cups of coffee per day and 41% in those who drank more than 4 cups16.

Coffee and risk of other liver diseases

Coffee drinking has also been related to a reduced risk of other liver diseases, thus suggesting a continuum of favourable effects of coffee on liver function. A systematic review published in 2014 suggested coffee consumption was associated with beneficial outcomes in patients with chronic liver disease, cirrhosis, hepatocellular cancer and non-alcoholic fatty liver disease17.

  • A 2009 review article concluded that patients with higher coffee consumption display a milder course of fibrosis, especially in alcoholic liver disease18.
  • A small cross-sectional North American study recruited 177 patients scheduled for liver biopsy over a period of 6 months19. They observed that caffeine consumption was associated with less severe hepatic fibrosis.
  • Data from the US National Health and Nutrition Examination Surveys (NHANES 1999-2010) suggests that higher intakes of coffee (including decaffeineated coffee) were associated with beneficially lower levels of liver enzymes20.

Chronic Liver Disease

  • An Italian cross-sectional study recruited 749 patients with chronic liver disease and looked for any association between alcohol and coffee consumption and the development of cirrhosis21. The results suggest a favourable effect of coffee, but because of the small numbers in some of their sub-groups, these results are not conclusive.
  • A Scottish study suggested that coffee drinking is associated with a reduced prevalence of cirrhosis in patients with chronic liver disease22.
  • Data from the US Multi Ethnic Cohort concluded that coffee drinking is associated with a reduced incidence of chronic liver disease. Compared to non-coffee drinkers, consuming 2-3 cups per day was associated with a 46% reduction in risk of death from chronic liver disease, and greater than 4 cups a day with a 71% reduction16.

Non-alcoholic fatty liver disease

  • Another Italian study recruited 137 patients with non-alcoholic fatty liver disease and compared this group with a group of 108 other patients23. The results indicate a possible favourable association with coffee consumption. However, because of the design used in this study (patients with one disease versus patients with other diseases), the findings should also be interpreted with caution.
  • A further North American study to investigate the effects of dietary behaviour in non-alcoholic fatty liver disease patients, using four continuous cycles of the National Health and Nutrition Examination Surveys (NHANES 2001 -2008), found caffeine intake to be independently associated with a lower risk of non-alcoholic fatty liver disease, suggesting a potential protective effect24.
  • A 2012 study correlated coffee caffeine consumption with the prevalence and severity of non-alcoholic fatty liver disease. Coffee caffeine consumption was associated with a significant reduction in risk of fibrosis among patients with non-alcoholic steatohepatitis25.
  • A Mexican case-control study looked at the antioxidant effect of coffee by measuring antioxidant enzymes and lipid peroxidation markers in patients with non-alcoholic fatty liver disease and in patients without non-alcoholic fatty liver disease. They found a high intake of coffee to have a protective effect against non-alcoholic fatty liver disease, however there was no significant difference in the antioxidant variables analyzed26.
  • Data from 728 adults in the Non-alcoholic Steatohepatitis Clinical Research Network (NASH-CRN) suggests that coffee intake was inversely associated with advanced fibrosis in patients with non-alcoholic fatty liver disease27.

Hepatitis C

  • A prospective cohort US study recruited 766 hepatitis C-infected patients and followed them up for nearly four years28. A total of 230 patients showed serious disease progression, e. g. cirrhosis or 2-point increase in Ishak fibrosis score (a histological grading of progression to fibrosis, with scores ranging from 0 to 6). Tea consumption was not associated with the study outcomes. However, regular coffee consumption was statistically significantly associated with lower rates of disease progression.
  • A French study developed to evaluate the impact of caffeine consumption on activity grade and fibrosis stage in patients with chronic hepatitis C found that caffeine consumption greater than 408 mg/day was associated with reduced histological activity in these patients29.
  • A study of patients with the Hepatitis C virus suggested that amongst those with a chronic infection, daily consumption of filtered coffee may have a beneficial effect on the stabilisation of the liver enzyme serum alanine aminotransferase (ALT)30.
  • Data from the Singapore Chinese Health Study, a population-based cohort of 63,275 adults, suggested that there was a strong dose-dependent inverse association between coffee intake and risk of non-viral hepatitis related cirrhosis. Compared to non-coffee drinkers, those who drank more than 2 cups per day had a 66% reduction in mortality risk. However, there was no association between coffee intake and hepatitis B related cirrhosis31.

If patients change their habits or diet as a result of their disease or its standard therapy, this can bias the observational study. Therefore it is important to assess whether such confounders are adequately taken into account. Case control-studies are particularly susceptible to bias, in particular when other patients are used as controls; prospective cohort studies are less susceptible to this type of bias.

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