Coffee not only helps you feel full of beans - it might add years to your life as well, two major studies have shown.

Scientists in Europe and the US have uncovered the clearest evidence yet that drinking coffee reduces the risk of death.

One study of more than half a million people from ten European countries found that men who downed at least three cups of coffee a day were 18% less likely to die from any cause than non-coffee drinkers.

Women drinking the same amount benefited less, but still experienced an 8% reduction in mortality over the period measured.

Similar results were reported by US scientists who conducted a separate investigation, recruiting 185,855 participants from different ethnic backgrounds.

Irrespective of ethnicity, people who drank two to three cups of coffee daily had an 18% reduced risk of death.

Each of the studies, both published in the journal Annals of Internal Medicine, showed no advantage from drinking either caffeinated or decaffeinated coffee.

Experts believe the antioxidant plant compounds in coffee rather than caffeine are responsible for the life-extending effect.

Previous research has suggested that drinking coffee can reduce the risk of heart disease, diabetes, liver disease, and some cancers.

Dr Marc Gunter, from the International Agency for Research on Cancer, who led the European study with colleagues from Imperial College London, said: "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.

"Importantly, these results were similar across all of the ten European countries, with variable coffee drinking habits and customs. Our study also offers important insights into the possible mechanisms for the beneficial health effects of coffee."

Dr Gunter's team examined data from 521,330 participants in the Epic (European Prospective Investigation into Cancer and Nutrition) study.

The investigation spanned  ten European countries including the UK, France, Denmark and Italy.

The Danes drank the most coffee by volume - 900ml per person per day - and the Italians the least.

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% of consumers were 12% less likely to die. Women in the same category had a 7% lower chance of death.

In terms of numbers of cups of coffee consumed, men and women who drank three or more cups had an 18% and 7% reduced risk of death respectively.

The US study focused on ethnicity because lifestyle habits and disease risk varies greatly among people from different races and cultures.

Participants included white Americans, African-Americans, Native Hawaiians, Japanese-Americans and Latinos.

The US researchers 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% consumed four or more cups.

People who drank one cup of coffee daily were 12% less likely to die than those who drank no coffee, the results showed. Drinking two to three cups of coffee reduced the chances of death by 18%.

Lead author Dr Veronica Setiawan, from the University of Southern California, 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."

She added: "Coffee contains a lot of antioxidants and phenolic compounds that play an important role in cancer prevention.

"Although this study does not show causation or point to what chemicals in coffee may have this 'elixir effect', it is clear that coffee can be incorporated into a healthy diet and lifestyle."

Both teams of researchers took account of other lifestyle factors, such as diet, that may have influenced their findings.

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."

Dr Tim Chico, reader in cardiovascular medicine at the University of Sheffield, said: "What can we conclude from these studies? The authors of both papers sensibly go no further than concluding that their results show that coffee drinking is not harmful.

"The only way to be certain whether or not coffee might make people live longer is to force many thousands of people to drink it regularly, while preventing many thousands of otherwise similar people to never drink coffee.

"A study like this is never going to take place, so we may never know the answer to this question.

"I don't think this study should lead anyone to drink more coffee in search of a health benefit that might not actually exist.

"It is useful to compare this to the proven benefits of physical activity. A 20-minute walk to a local coffee shop will definitely provide many health benefits, even if you don't actually go in and buy anything."