Drinking up to five cups of coffee every day could halve the risk of hepatocellular cancer, say researchers.
What is more, researchers found that the higher one's coffee consumption, the lower the risk of hepatocellular cancer (HCC), with up to five cups of coffee each day associated with a 50 percent lower HCC risk.
Even decaffeinated coffee intake was found to reduce the risk of HCC, but to a lesser effect, the team reports.
Lead study author Dr. Oliver Kennedy, of the University of Southampton in the United Kingdom, and colleagues recently reported their findings in BMJ Open.
People with liver disease have the greatest risk of developing HCC, particularly those whose liver has been damaged through infection with hepatitis B or C, chronic liver inflammation, autoimmune disease, or alcohol abuse.
But according to Dr. Kennedy and colleagues, increasing coffee consumption may help to reduce the likelihood of developing HCC, even among adults with pre-existing liver disease.
Just one coffee per day linked to 20 percent lower HCC risk
The researchers came to their conclusion by conducting a systematic review and meta-analysis of more than 26 observational studies, which included information on more than 2.25 million adults.
The team looked at the coffee intake of the participants - including how many cups they consumed each day, as well as whether the coffee was caffeinated or decaffeinated - and whether or not this might be associated with the risk of developing HCC.
The analysis revealed that drinking one cup of coffee daily was associated with a 20 percent reduced risk of HCC, drinking two cups of caffeinated coffee per day was linked to a 35 percent reduction in HCC risk, while the risk of HCC was halved with consumption of up to five cups of caffeinated coffee daily.
Drinking decaffeinated coffee was also linked to a lower risk of HCC, though to a lesser extent than caffeinated coffee.
The protective effect of coffee against HCC was identified among both existing coffee drinkers and those who do not normally consume the beverage.
The researchers say that there was little available data to determine whether drinking more than five cups of coffee daily might lower HCC risk.
Coffee may have a 'significant effect on liver cancer risk'
Previous studies have suggested a role for coffee intake in reducing the risk of liver cancer, and Dr. Kennedy and colleagues believe that their latest study supports such an association.
"Coffee is widely believed to possess a range of health benefits, and these latest findings suggest it could have a significant effect on liver cancer risk," says Dr. Kennedy.
"We're not suggesting that everyone should start drinking five cups of coffee a day though. There needs to be more investigation into the potential harms of high coffee-caffeine intake, and there is evidence it should be avoided in certain groups such as pregnant women.
Nevertheless, our findings are an important development given the increasing evidence of HCC globally and its poor prognosis."
Dr. Oliver Kennedy
The researchers speculate that the antioxidant, anti-inflammatory, and anti-carcinogenic compounds in coffee may help to explain the link between coffee intake and a lower risk of liver cancer.
"Our findings suggest a central role for caffeine, given that the association was weaker for decaffeinated coffee," the team notes.