Humanity drinks around 2bn cups of coffee every day. The good news for those who contribute to that figure is that regularly consuming moderate amounts does not appear to be harmful. There may even be health benefits. Experiments conducted in vitro and in animals have long shown that some components of coffee, including cafestol, kahweol, caffeine and chlorogenic acids, can reduce inflammation as well as cell damage caused by a chemical process known as oxidation.

When a team led by Marzieh Moeenfard of the University of Porto looked more closely, they found that the potential benefits ran deeper. She reported in the Journal of Cellular Biochemistry in 2016 that cafestol and kahweol (which tend to be more prevalent in unfiltered than in filtered coffee) arrested tumour growth by making it less likely that new blood vessels would form around tumour cells, and that chlorogenic acids inhibited the formation of carcinogens within the body. This suggested coffee might be good for fending off cancer.

One follow-up study led by Jin-Kyoung Oh of the Karolinska Institute in Stockholm reported that post-menopausal women who claimed to drink three or four cups of coffee per day were significantly less likely to develop breast cancer than women who said they drank up to two cups. Similar work in Japan suggested that those who said they drank three or more cups every day had a reduced risk of developing liver cancer.

Because caffeine is a stimulant that improves mood and combats tiredness, its presence in coffee has prompted some to test whether it reduces the risk of a person developing psychiatric and neurological diseases like Alzheimer’s, Parkinson’s and depression. Some have found beneficial effects. For example, Hong Chien-Tai of Taipei Medical University reported in 2020 that in patients with Parkinson’s who consumed caffeine regularly, their disease progressed more slowly than in those who abstained.

Other findings, whether on cancer or mental health, have yielded mixed results. The uncertainty may well come down to the multitudes that coffee contains. Beans are sourced from different species, roasted in different fashions and served up in a variety of drinks of different sizes and strengths. Still, moderate consumption seems, at worst, harmless.

Overindulgence has clearer-cut consequences. Ingesting more than 400 milligrams of caffeine daily (an espresso contains around 60) has been found to lead to headaches, nervousness, irritability, muscle tremors and insomnia. It is also associated with mental-health conditions such as anxiety, and can make chronic health problems, like heart disease, worse by increasing blood pressure. The effects of overdosing on coffee’s other active ingredients are unclear.

But these are not the only risks associated with drinking coffee. Many lace their cup with additives like milk, sugar, cream and syrup, chronic overconsumption of which can also cause harm. A study of over 46,000adults published in the Journal of Nutrition in May is suggestive. The results showed that participants who drank between one and three cups of coffee per day were roughly 15 percent less likely to die during the next decade than those who consumed none. That said, the benefit vanished if they stirred more than around a teaspoon of cream or half a teaspoon of sugar into their drink.

To maximise the benefits, therefore, don’t overdo the cups and take it as black—and as bitter—as you like. ■

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