Quite a lot, and most of it is reassuring. Large studies following hundreds of thousands of people have found that regular coffee drinkers have a lower risk of chronic liver disease, cirrhosis and liver cancer than people who don't drink coffee. These are observational studies, so they show a link, not proof that coffee itself does the protecting.
What have the biggest studies found?
Three pieces of research come up again and again.
- Cirrhosis. A 2016 meta-analysis (Kennedy and colleagues) pooled nine studies with more than 430,000 participants. Each extra two cups of coffee a day was associated with a 44% lower risk of cirrhosis.
- Liver cancer. A 2017 meta-analysis by the same team, covering 26 studies and more than 2 million people, found that two extra cups a day went with a 35% lower risk of hepatocellular carcinoma, the most common type of liver cancer.
- Chronic liver disease. A 2021 study of nearly 495,000 UK Biobank participants, followed for a median of almost 11 years, found that coffee drinkers had a 21% lower risk of developing chronic liver disease and a 49% lower risk of dying from it than non-drinkers. The lowest risk was seen at around 3 to 4 cups a day.
In the UK Biobank study, the link held for ground, instant and decaffeinated coffee. Ground coffee, which includes espresso, showed the strongest association.
So does coffee protect the liver?
We can't say that yet. All of these findings come from observational research: people reported how much coffee they drank, and researchers looked at who later developed liver disease. That leaves room for other explanations.
- Other habits. Coffee drinkers may differ from non-drinkers in diet, alcohol, smoking or income. Researchers adjust for these factors, but never perfectly.
- Reverse causation. People who already feel unwell, or who have been told their liver is struggling, may cut down on coffee. That would make non-drinkers look less healthy for reasons that have nothing to do with coffee.
- One snapshot. The UK Biobank study asked about coffee once, at the start. Habits change over ten years.
The authors of these studies say this themselves. There are possible biological explanations being studied, such as compounds in coffee that act on inflammation and scarring in the liver, but much of that work is in cells and animals. What we have is a consistent, fairly strong association across many populations, not proof.
How much coffee is safe to drink?
The European Food Safety Authority (EFSA) has concluded that for healthy adults:
- up to 400 mg of caffeine a day does not raise safety concerns
- single doses of up to 200 mg do not raise safety concerns
- in pregnancy, up to 200 mg a day does not raise concerns for the baby
How much caffeine is in a cup varies a lot with the coffee, the size of the cup and how it is made, so these are guides rather than a cup count. Caffeine can also disturb sleep in some people, even at around 100 mg close to bedtime.
Does the way you make coffee matter?
For the liver, the studies don't give a clear answer, although ground coffee showed the strongest link in the UK Biobank data. For cholesterol, the brewing method does matter. A meta-analysis of randomised trials (Jee and colleagues, 2001) found that unfiltered coffee raises total and LDL cholesterol, while filtered coffee has very little effect. The cause is a natural oil in coffee called cafestol, which a paper filter traps.
This is worth knowing in Cyprus, where traditional Cypriot coffee is boiled and not filtered. That doesn't mean you have to give it up. If you have high cholesterol, though, it is a good thing to mention to your doctor, along with how many cups you drink.
What if I already have a liver condition?
Coffee is not a treatment. If you have fatty liver disease, hepatitis, cirrhosis or any other liver condition, talk to your doctor before changing anything, and keep following the treatment and advice you were given. The same goes if you take regular medication, because caffeine can interact with some medicines. Your doctor or pharmacist can check.
It also helps to keep the bigger picture in mind. The things with the clearest effect on liver health are well known: limiting alcohol, keeping a healthy weight, moving more and getting vaccinated against hepatitis B where recommended. Coffee does not cancel out heavy drinking.
What does this mean for an ordinary coffee drinker?
If you already enjoy coffee and it agrees with you, the research gives no reason to stop, and some reason to feel relaxed about your habit, as long as you stay within EFSA's caffeine guidance. If you don't drink coffee, there is no need to start for your liver's sake. And what goes into the cup counts too: a lot of sugar or syrup adds free sugars the liver could do without.
FAQ
How many cups of coffee a day are linked to a healthier liver?
In the UK Biobank study, the lowest risk of chronic liver disease was seen at about 3 to 4 cups a day. That is an observed association, not a recommended dose, and you should stay within EFSA's limit of 400 mg of caffeine a day.
Does decaf count?
In the UK Biobank study, decaffeinated coffee was also linked to a lower risk of liver disease. This suggests that compounds other than caffeine may play a part, but it hasn't been proven.
Is Cypriot coffee bad for cholesterol?
Unfiltered, boiled coffee raises LDL cholesterol in trials, while filtered coffee has very little effect. If your cholesterol is high, ask your doctor whether to switch some of your cups to filtered coffee.
Sources: Kennedy OJ et al., Systematic review with meta-analysis: coffee consumption and the risk of cirrhosis, Alimentary Pharmacology & Therapeutics 2016, 43(5):562, Kennedy OJ et al., Coffee, including caffeinated and decaffeinated coffee, and the risk of hepatocellular carcinoma: a systematic review and dose–response meta-analysis, BMJ Open 2017, 7:e013739, Kennedy OJ et al., All coffee types decrease the risk of adverse clinical outcomes in chronic liver disease: a UK Biobank study, BMC Public Health 2021, 21, EFSA, Scientific opinion on the safety of caffeine (EFSA Journal 2015, 13(5):4102), Jee SH et al., Coffee consumption and serum lipids: a meta-analysis of randomized controlled clinical trials, American Journal of Epidemiology 2001, 153(4):353.
