Drinking around three cups of coffee a day has been linked to a lower risk of death “from any cause” in two new large-scale studies.
The habits of coffee-lovers were shown to add years to their life – with high coffee consumption shown to reduce the risk of death from diseases related to circulation and digestion in particular.
While scientists say more research is needed to prove coffee is definitely behind the effects observed in the studies, experts believe the antioxidant plant compounds found in the drink, rather than its caffeine, are responsible for its potentially life-extending effect.
Researchers from Imperial College London and the International Agency for Research on Cancer (IARC) analysed data on the health and coffee-drinking habits of more than half a million people from 10 European countries, including the UK.
They found men who drank at least three cups of coffee a day were 18 per cent less likely to die from any cause than non-coffee drinkers, with women experiencing an eight per cent reduction in mortality over the same period.
Meanwhile, American scientists conducted a separate investigation into the effect of coffee on the health of more than 185,000 participants from different ethnic backgrounds.
People who drank one cup of coffee daily were 12 per cent less likely to die than those who drank no coffee, irrespective of ethnicity, while drinking two to three cups of coffee appeared to reduce the chances of death by 18 per cent.
Experts praised the robust nature of the studies, but warned that further research was needed to prove that the effects observed were caused by the coffee itself, and not other factors.
The US study’s lead author, Dr Veronica Setiawan, from the University of Southern California, said the chemical make-up of the popular beverage was a possible explanation for the findings.
“Coffee contains a lot of antioxidants and phenolic compounds that play an important role in cancer prevention,” she said.
“We cannot say drinking coffee will prolong your life, but we see an association. If you like to drink coffee, drink up! If you’re not a coffee drinker, then you need to consider if you should start.”
Whether the coffee contained caffeine or was decaffeinated did not appear to make a difference in the two studies, both published in the journal Annals of Internal Medicine.
The studies were adjusted for a number of lifestyle factors, such as smoking and diet, to try and isolate and analyse the effects of coffee drinking on health and mortality rates.
Commenting on the research, statistics expert Professor Kevin McConway, from The Open University, said both papers were “well-conducted and large, and show similar results across several different populations and ethnic groups”.
“As a coffee drinker myself, they do reassure me that my habit probably isn’t bad for me,” he said. “However, if I didn’t already drink coffee, I’m not sure that they would persuade me to take it up for the good of my health.
“That’s because the size of the potential protective effect of coffee, in these studies, is not very large; because we can’t be sure what is causing what; and because, even if coffee drinking is somehow directly improving people’s health on average, neither study throws much light on exactly how it might do that.”
Professor Naveed Sattar, professor of metabolic medicine at the University of Glasgow, said the European study was “a very nice paper, written by an excellent group and very well done”.
However, he also raised doubts about drawing conclusions on cause and effect from the data presented in the research, because people who are sick may drink less coffee.
“When some, perhaps many, people are unwell they cut their intake of coffee so that in any given population, many who do not drink coffee or drink less of it may be more unwell,” he said.
“Whilst the authors have done their best (and better than most) to limit this potential bias, such a bias is very hard to fully overcome.”
The European study used data from 521,330 participants in the European Prospective Investigation into Cancer and Nutrition (Epic) study, spanning countries including the UK, France, Denmark and Italy.
After 16 years, almost 42,000 people taking part in the study had died from a range of causes including cancer, circulatory disease, heart failure and stroke.
Compared with non-coffee drinkers, men in the top 25 per cent of consumers were 12 per cent less likely to die. Women in the same category had a 7 per cent lower chance of death.
The US investigation had 185,855 participants, including white Americans, African-Americans, native Hawaiians, Japanese-Americans and Latinos. The study focused on ethnicity because lifestyle habits and disease risk varies greatly among people from different races and cultures.
This study also looked at death rates over a period of 16 years. A quarter of participants drank two to three cups of coffee per day and 7 per cent consumed four or more cups.
Coffee is the world’s favourite beverage, with an estimated 2.25 billion cups drunk globally each day.
Britons consume around 55 million cups of coffee per day, according to the British Coffee Association.
Sir David Spiegelhalter, Winton professor for the public understanding of risk at Cambridge University, said: “If these estimated reductions in all-cause mortality really are causal, then an extra cup of coffee every day would on average extend the life of a man by around three months, and a woman by around a month.
“Pro-rata, that’s as if that cup of coffee puts, on average, around nine minutes on a man’s life, and around three minutes on a woman’s. So perhaps we should relax and enjoy it.”
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