Fears have been raised over the safety of high-caffeine energy drinks after an inquest heard they could have brought on a fatal heart attack.
Red Bull contains approximately the same amount of caffeine as a cup of coffee

Alfredo Duran, 40, who drank four cans of Red Bull every night, collapsed and died after working a supermarket night shift.

An inquest into his death heard that he had an enlarged heart and that caffeine may have triggered an attack.

Dr Ian Roberts, a pathologist, said the amount of Red Bull Mr Duran drank could have contributed to his death.

Levels found during the post mortem examination were not fatal, but were dangerous for a man with an underlying heart condition.

He said: "For an individual with this condition, the risk of problems with the heart is increased by stimulants such as caffeine and may be triggered by levels which would have no effect on people with a normal heart.

"My feeling is, given the evidence available, it was a cardiac arrest, possibly contributed by sub-toxic caffeine ingestion."

The Oxford inquest heard that paramedics were called to help the Bolivian supermarket worker when he collapsed in an aisle in September 2006.

Mr Duran, who had two children, had worked at the Asda supermarket in Wheatley, Oxon, since 2003, for a minimum of two night shifts a week, from 11pm until 6am.

At the time of his death he would frequently work up to five night shifts a week.

Colleagues said it was not unusual to find at least four empty cans of Red Bull when Mr Duran, of Oxford, had been working.

The Oxfordshire coroner, Nicholas Gardiner, described him as a healthy man and compared his death with sudden adult death syndrome as he recorded a verdict of death by natural causes.

He added that the cause of death was unascertained.

Last year, Red Bull sold 3.5 billion cans and bottles in 140 countries.

The drink's manufacturers claim it "vitalises the body and mind" and has been "specially developed for times of increased mental and physical exertion".

It is popular among students, nightclubbers, workers and drivers attempting to say awake for long periods.

The drink contains about the same amount of caffeine as a cup of coffee, but has been banned in a number of countries amid fears it could cause an increase in *lo** pressure.

A US study last year found healthy volunteers given two energy drinks a day for a week experienced significant increases in both heart rate and *lo** pressure.

The makers of Red Bull denied it could cause harm, but recommended that no more than two cans were drunk a day.

A spokesman said clinical tests and "numerous" toxicological evaluations by independent experts had concluded it was as safe as any other drink for adults.