Health benefits of black coffee

Heart protection

For decades, coffee was linked to poor heart health. But research has now consistently suggested that it can protect the organ.

Scientists from the University of Colorado, who examined data on the diet and medical records of more than 15,000 people, found that, compared to people who didn’t drink coffee, for every extra cup of coffee drunk per week, there was a 7 per cent drop in the risk of heart failure and an 8 per cent reduction in stroke risk.

Experts believe this effect is down to the biologically active compounds (those that have a physiological effect on the body) in coffee, of which there are more than 100. In particular, polyphenols are thought to reduce oxidative stress, which occurs when there is an imbalance between the beneficial and harmful molecules in the body, and inflammation, protecting the heart from damage.

However, all coffee studies are based on observational evidence, meaning they can’t prove that it was the drink that improved participants’ health.

While it could be that the compounds in coffee protect against illness, there may be other factors at play, such as coffee drinkers engaging in other healthy behaviours.

Reduced risk of Type 2 diabetes

Maintaining a healthy weight, exercising and following a healthy diet are the evidence-backed ways of reducing the risk of Type 2 diabetes. However, studies suggest that habitually drinking coffee could protect against the condition.

A 2014 review from Harvard University researchers, which looked at 28 prior studies, found that people who drank one cup daily were less likely to develop Type 2 diabetes, compared to non-coffee drinkers. The benefits increased with every cup of coffee consumed, up to a 33 per cent lower risk among those who drank six cups a day.

The scientists suggested that the acids in coffee may improve blood sugar levels, while its high magnesium content may offer further protection.

“The phytonutrients [compounds produced by plants] associated with that were caffeic acid and chlorogenic acid,” says Prof Collins, who is also co-director of the food and nutrition research programme at Hunter Medical Research Institute. “Those two chemicals have been shown to help your muscles use up glucose in your blood.”

Coffee seems to protect against developing Alzheimer’s and Parkinson’s, research has repetitively shown.

Scientists in Canada who studied this phenomenon suggested in a 2018 paper that this effect could be down to compounds called phenylindanes, which are produced when coffee beans are roasted.

They are thought to prevent a build-up of proteins called amyloid and tau, which are toxic to brain cells.

Cancer prevention

Studies have found that some cancers, especially liver and womb cancer, are less common among coffee drinkers. There’s also some evidence that the drink may protect against mouth and skin cancers.

While the exact mechanisms behind this are unclear, Prof Collins says two phytonutrients found in coffee, called cafestol and kahweol, seem to be behind this effect.

“They actually have direct cancer protection that seems to be associated with their anti-inflammatory ability,” she says. “They are essentially the front line of chemicals that’ll take out cancer-causing compounds.”

Caffeic acid and chlorogenic acid are also thought to prevent cancer development by neutralising harmful chemicals called free radicals, Professor Collins adds.

Mood and depression

The mental effects of coffee are obvious – you’re left feeling more alert, attentive and energised in the hours after drinking a cup. However, beyond these short-term changes, coffee seems to have long-lasting mental health effects.

One review, from researchers in China, found that there was a 24 per cent lower risk of depression among the biggest coffee drinkers, who were downing four-and-a-half cups a day, compared to those who had less than one cup per day.

This is thought to be down to the caffeine in coffee increasing the expression of neurotransmitters in the brain, such as the “happy hormone” dopamine.

However, tolerance to caffeine varies from person to person, depending on their weight, metabolism, genetics and whether they’re taking certain medications. As well as perking you up, coffee drinking can also lead to anxiety, restlessness and insomnia.

Weight management and metabolism

As well as being low in calories, coffee may also boost the body’s calorie-burning capabilities by activating brown fat, research suggests.

The purpose of brown fat, typically stored around the neck, is to generate body heat when exposed to cold temperatures, which it does by burning calories. It is different from the more common white fat, which builds up if people eat too many calories.

Scientists at the University of Nottingham studied brown fat in lab tests and results showed that coffee activates it, which could ultimately help with weight loss.

Longer life expectancy

Coffee could increase lifespan, studies have suggested.

Researchers in Australia, who monitored the health and coffee-drinking habits of around 450,000 people for more than a decade, found that people who drank two to three cups of ground coffee a day were up to 27 per cent less likely to die early.

The team said rather than caffeine, other compounds in coffee, such as caffeic acid and chlorogenic acid, were likely behind this effect.

Eases some headaches

While too much caffeine can cause headaches, research suggests that coffee can also ease them. “The stimulant seems to [enhance the potency] of painkillers by a substantial amount,” says Prof Collins.

One review from the University of Oxford found taking paracetamol or ibuprofen for a migraine or tension headache reduced pain by 25 per cent. However, people who took painkillers alongside caffeine said their pain levels halved.

What type to drink

It’s good news for those who don’t enjoy a bitter taste, as it doesn’t actually matter whether you take your coffee black or add a drop of milk – the health benefits will be the same.

“Most of the research studies are testing black coffee and most are done in the United States where black coffee drinking is more common,” says Prof Collins. “But there’s no reason to believe that the results would be appreciably different if you’re adding a bit of milk to your coffee.”

Is there a healthy way to prepare coffee?

When it comes to how the coffee is prepared, some studies suggest that the Scandinavian method – which involves boiling the coffee – may increase risk of cardiovascular disease.

“So methods such as filter and espresso which do not use boiling water are probably better,” says Dr Duane Mellor, a registered dietitian at Aston Medical School in Birmingham. “If using a French press, maybe letting the water cool slightly before adding it to the coffee could be sensible.”

Decaf or caffeinated?

It doesn’t matter too much whether you opt for regular or decaf coffee. “Beneficial compounds are still there in the decaffeinated coffee,” says Prof Collins. “If you’re the sort of person who has one coffee and is awake until 2am, drink decaf.”

However, for those looking for a boost to their mental health, studies suggest caffeinated coffee is required.

How much you should be drinking?

Studies suggest around 200 to 500mg of caffeine per day – which roughly equates to two to five cups – is the range that should be consumed to harness coffee’s health benefits.

Above this range, the benefits (reduced risk of disease) disappear, while risks (difficulties sleeping, anxiety and increased blood pressure) increase, says Dr Mellor.

However, it is vital to note the method of coffee preparation – instant, espresso machine, filter – influences the amount of caffeine present in the beverage. “This needs to be considered when thinking about ‘total cups per day’ as well,” says Dr Harry Smith, a nutrition research scientist at the personalised nutrition company Zoe.

For example, there is around 60mg of caffeine in an espresso, rising to 100mg in a mug of instant coffee and 140mg for filter coffee.

Additionally, caffeine content can also vary dramatically depending on where a coffee is bought. An espresso at Caffè Nero contains 45mg of caffeine, while the same drink at Pret has 180mg, according to research from Which? published last year.

When you should drink it

The effects of caffeine on sleep is the main consideration when timing your coffee.

“On average, caffeine can stay in our system for approximately five hours but this number can range between one-and-a-half to nine-and-a-half hours depending on the individual,” says Dr Smith.

This means that drinking a coffee in the afternoon could leave some tossing and turning, while others can have the beverage in the evening with no problems.

“The general advice is to confine caffeine consumption to the early portion of the day,” notes Dr Smith. “The closer it is consumed to bed time the more of an impact it is likely to have on your sleep quality.”

However, research from Dr Smith and colleagues at the University of Bath, published in the British Journal of Nutrition in 2020, suggests that it is best to eat breakfast before your first mug of the day. They found that consuming a strong black coffee on an empty stomach after a poor night of sleep triggered a spike in blood sugar. If repeated over time, this could increase the risk of developing Type 2 diabetes.

Potential risks and considerations

It’s important to consume coffee in moderation. More than 600mg of caffeine per day has been linked with insomnia, irritability and high blood pressure.

Too much of the stimulant over a short period of time is definitely associated with greater risk of headaches, anxiety, chest pain, irregular heartbeat and in some cases death, if consumed in extremely high doses, as it can trigger a cardiac arrest, says Dr Smith. Fatalities usually occur when caffeine has been consumed in the form of powders, rather than coffee.

“If anyone is worried about [the side effects of coffee] they should talk to their GP or qualified medical professional,” he adds.

Pregnant women are advised to limit coffee intake to around two cups per day (200mg of caffeine) because studies have linked the stimulant with a low birth weight.

However, Prof Collins believes women planning to get pregnant or in the first two trimesters should err on the side of caution and avoid caffeinated coffee. “It’s really unclear how much caffeine is in your coffee,” she says. “You could end up having way more than you think.”