Coffee addicts and enthusiasts habitually say drinking the bitter brew makes life worth living, but drinking coffee may also help them live longer, two major international studies published on Monday say.
Experts warned, however, that the U.S. and European reports, published in the Annals of Internal Medicine, was not able to show that coffee was the only the reason that many drinkers seemed to have longer lives.
On the contrary the studies were observational in type meaning they showed a connection between coffee-drinking and a tendency toward longevity, but was inadequate towards proving cause and effect.
The first study, led by the International Agency for Research on Cancer (IARC) and Imperial College London, surveyed more than fifty thousand people across 10 countries in Europe.
Those who consumed about three cups a day were inclined to live longer than non-coffee drinkers, said the study, which researchers explained as the largest investigation of the effects of coffee-drinking in a European population.
“We found that higher coffee consumption was associated with a lower risk of death from any cause, and specifically for circulatory diseases, and digestive diseases,” said lead author Marc Gunter of the IARC, formerly at Imperial’s School of Public Health.
“Importantly, these results were similar across all of the 10 European countries, with variable coffee drinking habits and customs.”
The second study surveyed more than 180,000 participants of different races in the United States. It found advantages to longevity if the coffee was caffeinated or decaffeinated.
Coffee drinkers had a lower risk of death because of heart disease, cancer, stroke, diabetes, and respiratory and kidney disease. Those who drank one cup a day had a 12 percent better chance of living longer compared with those who were not fond of coffee.
Those who drank two or three cups per day saw an even higher 18 percent better shot at life.
“We cannot say drinking coffee will prolong your life, but we see an association,” said lead author Veronica Setiawan, an associate professor of preventive medicine at the Keck School of Medicine of University of Southern California.
“If you like to drink coffee, drink up! If you’re not a coffee drinker, then you need to consider if you should start.”
Coffee is one of the most widespread drinks in the world. Some 2.25 billion cups are consumed every day.
Many previous studies have acclaimed the benefits of coffee-drinking, saying the beverage gives anti-oxidants, may recover liver function and decrease inflammation.
However, coffee may also be risky or some people, and pregnant woman and children are advised to stay away from caffeine, which can be fatal in high doses.
A report from the IARC last year that said drinking very hot beverages — coffee, tea or otherwise — is one of the likely causes of cancer of the oesophagus, the tube that runs from the throat to the stomach.
Experts who were not a part of the latest studies urged restraint in interpreting the results.
For instance, the European study left out people who had cancer, heart disease or diabetes, in other words it studied people over 35 who were already more or less healthy.
It also questioned about coffee consumption only one time, at the beginning, and did not revise this figure over the span of the study, which included an average follow-up time of 16 years.
Not the least, it found signs of an association between women who consumed large amounts of coffee and a higher risk of cancer death, but under played this finding, saying it “may be spurious.”
The “conclusions will not lead me to start drinking coffee or to recommend people drink more coffee as a way to lessen their risks for heart disease,” said Naveed Sattar, professor of metabolic medicine at the University of Glasgow.
“I remain unconvinced that the link between coffee and heart disease represents a true cause and effect relationship and that coffee is truly protective, regardless of how large a study suggests this.”
Sattar said that one disadvantage of the research was that the fact that people stop drinking coffee — or drink less of it — when they are ill, a “bias is very hard to fully overcome.”
David Spiegelhalter, a professor at the University of Cambridge, labelled the research as “huge in size and carefully done,” but however, not successful in proving cause and effect.
“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,” he added.
“So perhaps we should relax and enjoy it.”