At one time coffee was almost universally considered a vice and “everyone” knew it was bad for them. However, in the last few years evidence has been mounting that coffee is, in fact, very good for people, and indeed especially for the liver.
Several studies have shown that a regular coffee habit can significantly reduce the risks of common liver cancers such as hepatocellular carcinoma (HCC), serious liver diseases such as fibrosis and cirrhosis, and inflammation of the liver.
Since the liver carries out hundreds of jobs in the body, drinking coffee regularly may be an easy and effective way of looking after this vital organ and health in general.
Drinking coffee has also been shown to have beneficial effects on other cancers (such as melanoma) and on type 2 diabetes, and is associated with lower death rates from many other causes.
Benefits of Coffee
The benefits of coffee have mainly been shown in black coffee consumed without sugar or artificial sweeteners, but the method of preparing the coffee appears to have little effect. Decaffeinated coffee has also been shown to be beneficial, but less so.
Coffee and Hepatocellular Carcinoma (HCC)
A study published in the British Medical Journal analyzed studies of over 2.27 million adults and found that drinking coffee reduced the risk of developing HCC in people with and without pre-existing liver disease. Drinking an extra two cups a day reduced the risk by 35 percent. In people with cirrhosis, the absolute risk of developing HCC is high, but drinking five cups of coffee a day halved the risk.
The researchers took into account other factors that affect the liver, such as alcohol consumption, smoking, overweight (measured by body mass index, or BMI), hepatitis B and C, and type 2 diabetes.
The researchers, led by Dr. Oliver Kennedy of the University of Southampton, cautioned against drinking more than five cups of coffee a day and warned that some people, such as pregnant women, should avoid drinking coffee because of the caffeine content.
Coffee and Liver Stiffness
A study published in the Journal of Hepatology last year (journal-of-hepatology.eu/article/S0168-8278(17)30147-2/fulltext) looked at the effect of coffee (and herbal tea) consumption on liver stiffness, which is a measure of the amount of scarring (fibrosis) of the liver that can lead to cirrhosis. They used data obtained on over 2,400 people taking part in the ongoing Rotterdam Study, and found that those who drank three or more cups of coffee or herbal tea a day consistently had lower liver stiffness, and these results were independent of BMI and other lifestyle factors.
What’s In the Coffee?
Everyone knows that coffee contains caffeine, which has had some bad publicity over the years because of side effects in some people, such as increased anxiety, palpitations, and insomnia. But coffee contains a wide range of other components, including vitamins B1, B2, B3 and B5, the minerals potassium and manganese, chlorogenic acid and diterpenes. Many of these compounds possess antioxidant, anti-inflammatory, antifibrotic and anticarcinogenic properties.
Caffeine is known to reduce cell proliferation in HCC. The liver breaks caffeine down into other chemicals, including paraxanthine (80%), theobromine (10%), and theophylline. Paraxanthine is known to slow down the growth of connective tissue, which might explain coffee’s beneficial effects on fibrosis, cancer, and cirrhosis of the liver.
The diterpenes cafestol and kahweol increase the activity of some liver enzymes, which may enhance the excretion of carcinogens. Cafestol and kahweol are found only in tiny amounts in filtered and instant coffees. Chlorogenic acid is one of over 1,000 polyphenols in coffee. Polyphenols are also found in red wine, tea, chocolate, fruits and legumes and are thought to reduce oxidative DNA damage.
How Much Coffee is Too Much?
Some people have a gene that makes them metabolize caffeine slowly and so caffeine has a stronger effect on them than on other people. For these people drinking too much caffeine, coffee is likely to keep them awake at night and lead to other side effects such as hypertension and “the jitters”. People with existing liver disease also tend to metabolize caffeine more slowly. Slow caffeine metabolizers, pregnant or lactating women, children, women on menopause medications, and those with cardiovascular disease are advised by most studies to limit their coffee consumption to one or two cups a day.
Consumed in moderation, especially when drunk black and without sugar, coffee, whether caffeinated or decaf, is now known to be beneficial for general health and can protect against liver cancer, other liver diseases, and a host of other diseases and conditions. To keep the liver healthy, reduce or eliminate alcohol and other toxins, exercise regularly, follow a sensible, varied diet with plenty of fruits and vegetables, and drink coffee.