The latest coffee study from China, showing that moderate coffee consumption is associated with a lower risk of death, is not news to me.
What this study, and the media reporting on it, fail to do is explore exactly why coffee has these life-prolonging properties.
Coffee is best known for caffeine. Caffeine is a natural chemical found in coffee that has stimulating effects on the body. It’s because of this stimulant effect that coffee often gets a bad reputation, but there’s so much more to coffee. Coffee has hundreds of other chemical compounds that are probably the secret to why coffee drinkers live longer, and it mostly has to do with better gut health (also known as gut microbiome diversity).
In our ZOE PREDICT study, we found that coffee drinkers generally had higher microbiome diversity, which was dose dependent, meaning the more coffee you drink, the more diverse your microbiome is. We can actually easily identify a coffee drinker by looking at their microbes, as specific microbes feed on the coffee bean.
Virtually all coffee drinkers have a microbe called lawonibacter asaccharolyticus in their gut, part of a series of “good” insects that ZOE’s nutritional science research has published in naturopathy, has been linked to healthier blood sugar and fat responses after eating, higher insulin sensitivity, and lower levels of insulin secretion.
While we can’t say exactly why coffee drinkers also tend to have higher microbiome diversity, this is likely due to the fact that coffee contains high numbers of various polyphenols and soluble fiber, both of which act as common nutrients for gut microbes.
Coffee beans are very high in fiber and research has shown that some of the fiber from the beans ends up in your cup of coffee. This is something often discussed by nutritionists, but there is research that has tested the fiber content in three types of coffee; espresso, drip and freeze-dried coffee. Researchers found that all three contain between 0.47-0.75 grams of fiber per 100 ml.
To translate: if you drink three 250 ml cups a day, that can add up to 6 grams of fiber a day. Most cups of coffee actually contain more fiber than a glass of orange juice and are much healthier. Considering the average daily fiber intake in the UK is a measly 18g, this is a significant jump in the right direction towards the recommended 30g/day.
Further research examined how this fiber is used in the gut. The fiber of the coffee was easily fermented by the human microbes, producing beneficial short-chain fatty acids that aid metabolism and our immune system. There is also a 60 percent increase in beneficial microbes (the beneficial Bacteroides-Prevotella group) after 14 hours of fermentation.
Another benefit of coffee is its high content of several polyphenols, a specific type of antioxidant or chemical defense that acts like rocket fuel for your microbes. These are produced in part by the complex fermentation process before roasting. Research has shown that coffee is the most important daily source of polyphenols in our diet. And polyphenols (antioxidants) help prevent and repair damage to cells and genetic material in the body.
Some of the other benefits of coffee include improved bowel movements, increased physical activity levels, protection against diabetes, and liver health protection.
But let’s be clear: I’m not suggesting that we should all drink six cups of coffee a day. Like anything, the right amount of coffee will be very personal to you and for those of us sensitive to caffeine, one cup is probably too much. The good news is that coffee’s benefits likely come from polyphenols and fiber, not primarily caffeine, as most studies show that decaf coffee has similar effects.
We all differ uniquely in how we respond to caffeine. Personally, I now have a fairly high tolerance and can enjoy two to three cups of black coffee a day before 4pm with no negative effects. Later in the day, I prefer decaf or herbal teas. I chose black coffee because milk and sugar can reduce the stated benefits and cause unfavorable spikes in blood sugar.
But many people will metabolize coffee much more slowly and it is these individuals who will experience jitters, anxiety and sleep disturbances. Experimenting with coffee or decaf will help you find a good spot where you won’t get unwanted anxiety, mood, or sleepless nights. Pregnant women should also be careful when consuming coffee. The recommended limit during pregnancy is about one and a half cups a day.
So for me, coffee is a delicious, complex drink, my gut microbes and I enjoy every day, and it just might help me live longer.
Tim Spector is Professor of Epidemiology at King’s College London