There are many health-related drawbacks associated with drinking too much coffee, such as insomnia and irritable bowel syndrome, but scientists believe they’ve uncovered a positive effect. Daily cups of coffee are linked with a reduced risk of cirrhosis liver disease, according to a recently published meta-analysis of nine previous studies.
The paper, published last month in Alimentary Pharmacology and Therapeutics, analyzed the data of 430,000 participants in total, of whom 1,990 had cirrhosis, from previous studies that examined the link between coffee and the disease.
In eight of the nine studies, researchers from Southampton University found that “increasing coffee consumption by two cups per day was associated with a statistically significant reduction in the risk of cirrhosis” and that the risks reduced as coffee consumption increased further.
Overall, they found that the risk of cirrhosis was 22% lower after one cup of coffee per day, 43% lower after two cups, 57% lower after three cups and 67% lower after four cups.
“An increase in daily coffee consumption of two cups is associated with a near halving of the risk of cirrhosis,” the authors wrote.
In all the studies, coffee consumption was measured in cups and based on responses by participants to interviews or questionnaires. Only one study asked about coffee preparation (whether it was boiled or filtered) and so, although coffee consumption was broadly similar across all studies, it’s possible that there were variations in the amount of caffeine consumed.
Crucially, the authors did not establish exactly how coffee might provide such protection, though they note that, “It is biologically plausible that coffee protects the liver against the inflammatory and fibrotic process leading to cirrhosis.”
Animal studies have shown that caffeine (not from coffee) protects against toxin-induced liver fibrosis. Non-caffeine elements could also play a role—after all, coffee contains other ingredients with anti-oxidative and anti-inflammatory properties.
However, it’s important to note that drinking a few cups of coffee won’t be enough on its own to counter the effects of an unhealthy lifestyle (cirrhosis is linked to both excessive alcohol consumption and obesity.)
Other scientists have urged caution over reading too much into the results. Hillel Tobias, a liver specialist and chairman of the American Liver Foundation’s National Medical Advisory Committee who was not involved in the study, told CNN that the effects of patient errors in self reporting and possible statistical mistakes mean that the paper might not hold up in practice.
Oliver Kennedy, lead author of the study, says it’s important to conduct clinical trials before making recommendations about how much coffee is healthy. And it’s worth bearing in mind that the positive effects of drinking coffee could well be countered by the negatives—such as an association with lung and bladder cancer, for example.