Coffee and Health
Coffee gets a bad press. We are used to thinking of it as something that may cause heart problems or be associated with cancer. We certainly know that it may cause problems sleeping, because of the caffeine it contains.
However, in the last few years, scientists have realised that coffee is actually not the villain. Drinking coffee is not linked to cancer, or to increased mortality from any form of cancer. In fact, it actually has a protective effect on heart health. On average, coffee drinkers get less heart disease than people who don’t drink coffee.
That is not to say that coffee does not have ill-effects on some people. There are plenty of people who experience a higher heart rate when they drink coffee, because of the effects of the caffeine. What, therefore, is the truth about coffee and health? This page unpicks the evidence to provide some answers.
What’s in a Coffee?
We all know coffee: brown drink, bitter taste, wakes you up.
But what exactly is it? What plant does it come from, and how does the coffee bean that we buy differ from what is harvested?
The short answer is that coffee is made from roasted coffee beans.
The long answer is that coffee beans are the seeds of the fruit of plants in the genus Coffea. The fruit of these plants are called cherries, and each cherry contains two seeds that are the coffee beans. There are two main species used in commercial coffee production, Coffea arabica and Coffea canephora var. Robusta. Arabica plants produce about 70% of the world’s coffee. Robusta beans are grown mainly in Asia, Brazil and South and West Africa, and are mostly used for instant coffee and some espresso blends. Both types of coffee plants grow only in tropical areas.
Robusta plants tend to be hardier than Arabica, and grow at lower altitudes. They are therefore easier to grow, which makes Robusta beans cheaper. Different coffee blends contain different amounts of Robusta and Arabica, and of different varieties of each.
After harvesting, coffee beans are fermented for about 24 hours, to make them easier to clean. This ensures that there is no fruit still stuck to the beans that might go off while they are being transported.
After that, coffee beans need to be roasted before they can be used to make coffee. The roasting usually happens in the country of consumption, rather than where the beans are harvested. The roasting also provides the flavour, with the length of roasting time being crucial. A longer roast gives a more bitter, but less acidic and less complex flavour.
That, therefore, is what is done to make your coffee. However, what’s actually in the coffee that you drink?
Coffee and Caffeine
We all know that coffee contains caffeine. We also know that caffeine is a stimulant—which is why coffee wakes you up. It can also affect your sleep if you drink it late in the evening, and some people find that it increases their heart rate.
However, it is impossible to say how much caffeine is contained in one cup of coffee.
This is because Robusta and Arabica beans contain different amounts. One reason why Robusta plants are hardier is because they contain more caffeine, which is nature’s insect repellent.
In essence, this means that cheaper coffee often contains more caffeine than more expensive types.
However, the precise amount will depend on the blend, and also the amount of coffee used to make each cup. For example, espresso coffee is often made with very little coffee—but the blend is likely to contain quite a lot of Robusta. Filter coffees tend to use more coffee, but it is more likely to be predominantly from Arabica beans, and therefore have less caffeine by volume.
More importantly, the precise effect of a cup of coffee will vary between individuals. Smokers metabolise caffeine more quickly. Older people metabolise it more slowly. Women also tend to metabolise it more slowly than men, on average. Some people also seem to be extremely sensitive to caffeine and may need to avoid it.
Other Nutrients in Coffee
Coffee is far more than simply ‘caffeine’. It also contains many other nutrients.
Importantly, of course, coffee is made with water. Coffee and tea therefore provide hydration—and count towards the volume of water you drink each day.
Coffee is also a plant-based drink—and therefore provides fibre (and for more about why fibre is important, see our page What is Fibre?). You consume a few grams of soluble fibre in each cup of coffee. In fact, for some people, coffee may be their main source of fibre (although this is not considered healthy).
Perhaps the most important molecules in coffee, however, are polyphenols.
These are natural defence chemicals in plants and give the bitter flavour. They are extremely beneficial for our gut microbiota, the microbes that live within our intestines. Drinking coffee therefore provides a boost to our gut microbes, and therefore to our health.
There is more about the importance of gut microbes in our page on the Gut Microbiome.
How Much is Too Much?
How much coffee is ‘too much’—or is there no upper limit?
The NHS advises people not to drink more than four cups of coffee a day, because it can increase your blood pressure.
The Mayo Clinic agrees with this assessment, adding that this is the same amount of caffeine as in 10 cans of cola, or two ‘energy drinks’.
Professor Tim Spector says that the science supports drinking “one to five coffees a day”. After six cups, you seem to lose the health benefits. However, he adds that the ‘sweet spot’ between one and five will vary between different people.
The key seems to be to balance the beneficial effect of the polyphenols with the downsides of drinking caffeine.
The Proven Benefits of Coffee
Coffee has several proven health benefits. These include:
Improving the diversity of your gut microbiome, possibly because of the soluble fibre and polyphenols.
Improving heart health, almost certainly because of the polyphenols it contains. However, medical advice remains that people with high blood pressure should not drink coffee because of the effects of the caffeine.
Possibly reducing the risk of certain cancers. Laboratory studies have found that two chemicals in coffee slow the growth of cancer cells. This may not translate into the human body, but there is some evidence that drinking coffee is associated with a lower risk of certain cancers, including liver, breast and colorectal.
Supporting cell repair around your body and reducing inflammation. The antioxidants and polyphenols in coffee can help to reduce inflammation and repair cells.
Lowering the risk of developing Type 2 diabetes. Several studies have found that people who drink four or more cups of coffee a day had a lower risk of developing diabetes than those who drank two or fewer cups. However, this may not be the coffee per se. Instead, people who drink coffee may be more active, which protects against developing diabetes.
Can improve bowel regularity. Coffee is a known laxative, and can therefore help to ‘get things moving’ if you are struggling a bit.
Reduces the risk of stroke. Contrary to previous received wisdom, recent studies have found that moderate coffee drinkers seemed to have a lower risk of stroke than those who drank no coffee.
Protects against developing liver disease. Studies have shown that coffee drinkers are less likely to develop chronic liver disease. In people who already had non-alcoholic fatty liver disease, coffee seemed to protect against liver fibrosis, which is the most common cause of chronic liver disease.
Some studies have also suggested that coffee is linked to a lower risk of Parkinson’s Disease, and other neurodegenerative and cognitive disorders. However, the lower risk is associated only with drinking five or more cups of coffee a day—which is, of course, not recommended because of the impact of the caffeine on your system.
Decaffeinated vs. caffeinated: differential health benefits?
Many people have turned to decaffeinated coffee to get the taste without the potential impact on sleep. However, does it have the same health benefits as ‘full fat’ coffee?
The answer to that is probably yes.
Professor Tim Spector, co-founder of ZOE, suggests that you should think of coffee as a drink made from fermented beans: simply another plant food.
Good-quality decaffeinated coffee seems to provide more or less all the same polyphenols as caffeinated coffee. However, it is worth buying whole decaffeinated beans in small quantities, and grinding them yourself, rather than buying ready-ground coffee. This is because decaffeinated coffee goes stale much faster than standard coffee because the beans are less dense.
A Final Thought
We are used to thinking about both tea and coffee as simply sources of caffeine.
However, all the evidence suggests that this is to underestimate both.
Instead, you should think about them both as plant-based foods, made up with water. As with all foods, quality really matters in terms of the health benefits. This provides a totally different perspective—and may change your views completely.