Study details

For the study, researchers analyzed data from 354,957 participants in the U.K. Biobank study, none of whom had cirrhosis or liver cancer. Participants were asked how much coffee they drank in a day, whether it was caffeinated or decaffeinated, and what additives like sugar or sweeteners they added to their coffee. Cases of liver disease or related mortality were assessed through linked health records.

The majority of participants reported drinking coffee, with 45.4% consuming one to two cups per day, 21.1% consuming three to four cups per day, and 11.5% drinking five or more cups per day. Around 15% of participants consumed decaffeinated coffee, and 3.4% reported using sugar or artificial sweeteners.

Over a median 13-year follow-up, the researchers found that drinking coffee was associated with a decreased risk of liver-related health conditions, with the risk decreasing with greater coffee consumption.

Drinking one to two cups of coffee a day was associated with a 20% lower risk of cirrhosis, a 24% lower risk of liver cancer, and a 31% lower risk of liver-related death. Meanwhile, drinking three to four cups a day was associated with a 35% lower risk of cirrhosis and liver cancer and a 41% lower risk of liver related death. Drinking five or more cups a day was associated with a 32% lower risk of cirrhosis, a 47% lower risk of liver cancer, and a 42% lower risk of liver-related death.

These associations were generally the same for those who drank both caffeinated and decaffeinated coffee, and for those who drank either sweetened or unsweetened coffee.

The researchers also used advanced MRI imaging and other analyses that found coffee drinkers had healthier liver protein profiles and less liver fat and inflammation than those who didn't drink coffee.

"We do see that probably, the liver benefit from the coffee is not from the caffeine, because we do see the similar benefit in the decaffeinated drinkers," Kim said. "So it seems more related to the anti-oxidative effect of the coffee."

Given the potential impact that heavy coffee drinking could have on blood pressure and heart rate, Kim said a moderate amount of three cups a day could be optimal "for getting the hepatoprotective effect, and at the same time minimizing any cardiovascular side effects."

Michelle Routhenstein, a preventive cardiology dietitian at Entirely Nourished who wasn't involved in the study, said that the results were unsurprising "since we have prior research suggesting coffee's positive role in liver and cardiometabolic health."

Routhenstein added that it was interesting the study found liver benefits were observed in both caffeinated and decaffeinated participants, suggesting that polyphenols and antioxidants are likely playing a role rather than caffeine alone.

"Coffee contains antioxidants such as chlorogenic acid, caffeic acid, and ferulic acid, which help reduce oxidative stress and inflammation, which may help protect liver cells from damage while also supporting cardiometabolic health," she said.

Lauren Manaker, a registered dietitian nutritionist who wasn't involved in the study, said the reductions in risk of cirrhosis, liver cancer, or liver-related death "are meaningful numbers for something as ordinary as a daily cup of coffee." However, she noted that "these are associations, not proof of cause."

That said, Manaker said the clinical outcomes alongside the MRI imaging strengthen the results of the study.

"Combining the three layers of evidence is the real strength," she said. "When the imaging and the proteins line up with the clinical outcomes, the overall picture becomes more believable than any one measure would be alone."