by That morning cup of coffee not only wakes you up for the day, it boosts the billions of friendly microbes that live in your digestive system. Because, according to a growing body of research, there is evidence that your espresso can have a positive effect on your microbiome – gut bacteria – leading to better overall health and even longer life.
“The microbiome includes legions of ‘good bacteria’ species that work together and individually to improve our health,” says Nicola Shubrook, registered nutritionist and functional medicine practitioner.
“More than ever, these microbes are seen to benefit our metabolic health, weight management and mental health,” she continues. “There are several compounds in coffee that act as prebiotics, meaning they feed the beneficial probiotic bacteria by providing them with nutrients necessary for growth and function.”
Coffee seems to have two effects on our gut flora. Firstly, caffeine itself acts as a stimulant, increasing the number of helpful bacteria in the gut. “The better the variety in your digestive system,” says Shubrook.
2023 study published in the journal Nutrients investigated the relationship between caffeine, coffee consumption and the colonic microbiome. The results showed that the richness of the microbiome was higher with regular coffee drinkers, which had increased the number of helpful people Alistipe and Facalibacterium types (considered to have preventive effects against liver fibrosis and cardiovascular disease), and lower levels of adverse Erypelatoclostridium, which causes bowel problems. This follows an earlier study which found that coffee consumption was associated with an increase in bifidobacterium, a microbe that is thought to help digest fiber and prevent infections.
Coffee also contains plant compounds called polyphenols, a category of compounds found naturally in plant foods, such as fruits, vegetables, herbs, spices, tea, dark chocolate, and wine. “Pophenols act as an anti-inflammatory antioxidant,” notes Shubrook. “They can help reduce cancer risk by neutralizing harmful free radicals, the chemicals that damage cells.”
The specific polyphenol in coffee is called chlorogenic acid. According to a 2020 study published in Experimental and Clinical Sciences, patients who consumed coffee rich in chlorogenic acid reduced their risk of Type 2 diabetes and non-alcoholic fatty liver disease – they also lost weight. The scientists concluded that this was probably related to an increase in intestinal bifidobacteria (one of the “good” ones).
Established studies have also shown that caffeine is good for your gut, stimulating the colon and leading to regular bowel movements. One study from 1990 showed that people who drank coffee tended to go to the loo 30 minutes after drinking a cup.
In so many ways, it seems that cup of joe is in love with the pan. But is there a better way to prepare and serve your coffee?
Black or milk?
Experts tend to agree that black coffee is better than cappuccino, latte or flat white. “Milk has been shown to inhibit the absorption of polyphenols,” says Julia Kopczyńska, a microbiologist at the Polish Institute of Biochemistry and Biophysics in Warsaw. “If you add a ton of cream or sugar, your coffee is dessert. Sugars will do more damage to your blood sugar levels than good coffee will.”
Which combination should I choose?
There are two main types of coffee beans: Arabica and Robusta. “Each one has different qualities at specific stages of roasting,” says Kopczyńska. “Although lighter roasts tend to have a higher caffeine content, they retain more antioxidants than darker roasts. Light roasted Robusta beans have more antioxidants than blonde roasted Arabica coffee.”
Most chain coffee shops in the UK use medium-roasted Arabica beans, although Costa sells a blend of Arabica and Robusta. Black Sheep Coffee also sells Robusta.
“My go-to is the Exhale Coffee, which is a dark Arabica grown with the highest level of antioxidants,” says Shubrook. “It’s the perfect black coffee, which I have no problem with.”
The length of time the beans are stored will also affect their polyphenol levels, with a reduction seen in coffee beans stored for 12 months or longer.
What about instant coffee?
While studies show that instant coffee may contain even more polyphenols and minerals than ground coffee, it also contains 100 percent more of a chemical called acrylamide—coffee substitutes can even have 300 percent more. “Acrylamide is present in coffee during the roasting process and if people are exposed to it in higher amounts, they may increase their risk of nerve damage and cancer,” says Kopczyńska.
There is no cause for alarm, however. “Coffee consumption, both ground and instant, is not associated with the development of cancer,” continues Kopczyńska. “However, the
The European Food Safety Authority (EFSA) recommends reducing the amount of acrylamide in our diet. That’s why we also recommend classic ground coffee over instant and substitutes.”
How many cups should I drink a day?
A recent study of centenarians living in the “longevity” Blue Zones of Sardinia and Ikaria, Greece, showed that almost all of them drank between two and three cups of black coffee a day. “Assuming that a cup of coffee is 8oz/220ml, the sweet spot is between two and three cups, with five being the upper limit,” says Kopczyńska.
Before you grind your beans or stamp your loyalty card, it’s worth considering the caffeine content of your drink. “Although coffee is beneficial, not everyone can metabolize it as efficiently,” Shubrook said. Kopczyńska agrees. “The maximum recommended amount of caffeine is 400mg per day. Anything over 600mg is linked to insomnia and high blood pressure.”
According to Kopczyńska, a cup of home-brewed coffee contains between 70mg and 140mg of caffeine, depending on the bean and brewing method. Meanwhile the average high street coffee has 180mg of caffeine. Pret espressos and cappuccinos are this size. Others can be higher: an average Costa cappuccino has 325mg – almost your entire recommended daily allowance in one cup.
You might be surprised to hear that most espressos are lower in caffeine than other types of coffee: a 30ml/1oz Caffe Nero espresso has 45mg of caffeine, while Starbucks only has 33mg. Greggs espresso clocks in at 75mg. (But a cup of espresso also has a much smaller amount of liquid than a latte or cappuccino.)
How should I prepare my coffee?
How you arrange your beans preserves different compounds, those that are beneficial, and those that are not so good for you. Brewed coffee contains cafestol and kahweol, chemicals called diterpenes. “Cafestol and kahweol are known for their anti-inflammatory, anti-diabetic, anti-cancer and polyphenol-preserving properties,” says Kopczyńska. “These are 30 times higher in unfiltered coffee.”
On the other hand, she says, unfiltered coffee contains oils that have been shown to raise cholesterol levels. “Refined coffee not only contains less coffee oils but also contains less caffeine compared to unrefined coffee brewing methods.”
If you can get around the fiddliness of using an Aeropress, a 2023 study published in the journal Foods this method has shown to be the best for preserving polyphenols. “In our study, the lowest total polyphenol content was found in coffee from the French press (133.90 g gallic acid / liter) and the highest was observed in the Aeropress brewer (191.29g gallic acid / liter),” the authors wrote . “The highest antioxidant potential and polyphenol content seen in the brew made in the Aeropress.”
Can I make my coffee healthier?
Adding natural spices – rather than sugars or syrups – can provide additional health benefits. “Cardamom is anti-inflammatory and regulates blood sugar levels,” advises Kopczyńska. “Ginger, a natural pain reliever, improves digestive health and lowers cholesterol. If you are using milk, turmeric added to a latte is known for its beneficial effects on metabolism and the immune system.”
