Drinking four cups of coffee a day could put you at higher risk of dying young, warn researchers.
They found more than 28 cups of coffee a week increases by half the chances of premature death in younger people.
But there was no change in risk for coffee drinkers aged over 55.
The findings come from a large scale American lifestyle study of 43,727 individuals aged 20 to 87.
The U.S. researchers suspect excessive coffee consumption may adversely affect the body’s metabolism, outweighing some of the known health benefits.
Individuals with a ‘genetic coffee addiction’ may be prone to these harmful effects, they suggest.
However, the latest study conflicts with a number of others showing moderate coffee drinking is linked with longevity.
During the study around 2,500 deaths were recorded, just under a third of which were due to heart and artery disease, over an average 16-year period.
Participants who consumed higher amounts of coffee were also more likely to smoke, and had less healthy hearts and lungs.
The risk of death from all causes rose by 56 per cent for both men and women younger than 55 years of age who drank more than 28 cups of coffee a week, the equivalent of four a day.
Younger women who consumed more than four cups a day had more than double the risk of dying from any cause compared with those who did not drink coffee, said a report in the journal Mayo Clinic Proceedings.
Researcher Steven Blair of the Arnold School of Public health, University of South Carolina, said: ‘Significantly the results did not demonstrate any association between coffee consumption and all-cause mortality in older men and women.’
Coffee contains a complex mixture of thousands of chemicals and is a double-edged sword that can have both good and bad effects on health.
Recent research has shown coffee to be a major dietary source of antioxidant, and it may reduce inflammation and boost brain function.
At the same time, coffee stimulates the release of adrenalin, inhibits insulin activity, increases blood pressure, and raises levels of homocysteine, a harmful chemical linked to heart disease and dementia.
Lead author Dr Junxiu Liu, from the University of South Carolina, said: ‘All of these mechanisms could counterbalance one another.
‘Research also suggests that heavy coffee drinkers may experience additional risk through potential genetic mechanisms or because of confounding through the deleterious effects of other risk factors with which coffee drinking is associated.
‘We hypothesise that the positive association between coffee and mortality may be due to the interaction of age and coffee consumption, combined with a component of genetic coffee addiction.’
Co-author Dr Carl Lavie, from Ochsner Medical Center in New Orleans, said: ‘There continues to be considerable debate about the health effects of caffeine, and coffee specifically, with some reports suggesting toxicity and some even suggesting beneficial effects.’
Dr Euan Paul, executive director of the British Coffee Association, said the study’s limitations may have skewed the findings.
The use of a questionnaire can result in recall bias, with people struggling to remember how many cups of coffee they’ve consumed in the past week, while other factors such as smoking and poor fitness could partly explain the link with premature death, he said.
Previous studies, like the current one, have found either no link between coffee consumption and heart deaths, or a positive effect, he added.
He said: ‘There is a growing body of data which suggests that coffee is perfectly safe when consumed in moderation – four to five cups a day – and as part of a balanced diet.
‘Caffeine is one of the most heavily researched compounds in the world today and there is a wealth of evidence suggesting that moderate coffee consumption may be associated with health benefits.
source: dailymail UK