Coffee consumption reduces the risk of
liver cancer by approximately 50%, the results of a meta-analysis published in
the online journal BMC Gastroenterology show.
A total of 16 studies published before May 2012 were included in the analysis.
Closer examination of the results suggested that the magnitude of the
protective effective of drinking coffee was higher among men than women and
also differed between patients of Asian and European origin. However, the
authors do not believe their results are definitive and call for further
research.
Liver cancer is an increasingly important
cause of illness and death in both men and women. Infection with hepatitis B or C
and excessive alcohol consumption are known risk factors for the malignancy.
Factors protective against the development of liver cancer are uncertain, and
the impact of coffee consumption is especially controversial.
A team of Chinese investigators therefore
performed a meta-analysis of case-controlled and cohort studies examining the
impact of coffee consumption and the risk of liver cancer.
Nine case-controlled and seven cohort
studies met the investigators’ inclusion criteria. A total of eleven studies were
conducted in Asia (nine in Japan) and five in Europe. All the studies provided
data on the risk of liver cancer according to coffee consumption. However,
there was little heterogeneity between the design of the studies. In
particular, the level of coffee consumption against which the risk of liver
cancer was assessed varied considerably, from as little as one cup each day to
as many as eight or more daily cups.
Overall, the investigators found that a
high coffee intake reduced the risk of liver cancer by 50% (OR = 0.50; 95% CI,
0.42-0.59). The protective effect of coffee consumption was similar in the
case control studies (OR = 0.50; 95% CI, 0.40-0.63) and the cohort studies (OR
= 0.48; 95% CI, 0.398-0.62).
Adjusting the results to take account of
liver disease status provided similar results (OR = 0.54; 95% CI, 0.46-0.66).
“The results of the current meta-analysis…suggest
that there is an inverse association between coffee consumption and liver
cancer among different groups according to consumption level,” comment the
investigators. “There were significant reductions of 50% in the risk of liver
cancer with the highest consumption of coffee compared with non/almost never
consumption.”
Stratifying the results by region suggested
that the degree of protection provided by coffee consumption was higher in Asia
(OR = 0.45; 95% CI, 0.36-0.56) than Europe (OR = 0.57; 95% CI, 0.44-0.75).
“The different results may be explained by
racial differences,” suggest the authors. “Differences in coffee drinking
habits may be a partial explanation for the discrepancy.”
Analysis according to sex showed that
drinking coffee reduced the risk of liver cancer by 62% in men (OR = 0.38; 95%
CI, 0.25-0.56) and by 40% in women (OR = 0.60; 95% CI, 0.33-1.10).
The authors note that caffeine has
antioxidant properties, possibly explaining the protective effect of coffee
consumption. However, the meta-analysis was unable to show the level of coffee
consumption needed to provide protection against liver cancer.
“The results of this meta-analysis
suggested that coffee consumption may be associated with a reduced risk of
liver cancer,” the authors conclude. “However, because of potential
confounding, this finding should be treated with caution. Further
better-controlled studies are needed to confirm this finding.”