A SUPERMARKET shelf-stacker's heart attack could have been caused by drinking too many energy drinks.

Forty-year-old Alfredo Duran - believed to have drunk up to four cans of Red Bull a night - died from a heart attack after collapsing in the soft drink aisle of the Asda store in Wheatley.

Mr Duran had an enlarged heart and yesterday both a pathologist and Oxfordshire coroner Nicholas Gardiner said the amount of caffeine he drank may have triggered the attack because of his condition.

Pathologist Dr Ian Roberts told an inquest although there was not enough caffeine in Mr Duran's body to be fatal alone, the levels could have contributed to his cardiac arrest.

He added: "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."

Red Bull has been banned by some countries, but last night its makers said there was no evidence it caused harm although it did recommend people should drink no more than two cans a day.

Mr Duran was found collapsed at the end of a night shift in September 2006. Attempts by staff and paramedics to revive the father-of-two were unsuccessful.

Supermarket cleaner Eduardo Campos said staff would regularly find at least four empty cans of Red Bull where Mr Duran had been working a nightshift.

Mr Duran, who had two sons, aged 17 and 22, worked at the supermarket from 2003 and was given a contract to work two night shifts a week.

Mr Duran, originally from Bolivia, regularly sought overtime and by the time of his death often worked five night shifts, from 11pm until 6am, every week.

The inquest heard there was no blood on the ground where he was found, nor any injuries on his body.

Recording a verdict of death by natural causes, Mr Gardiner described Mr Duran, of Randolph Street, East Oxford, as a healthy man and compared his death to sudden adult death syndrome.

He added that the cause of death was unascertained.

Outside the hearing, Mr Duran's widow Mariana de Jesus Ortiz said: "I am not satisfied with the outcome. He was a healthy man, young and fit and we don't know why he died."

A spokesman for Red Bull said: "No one anywhere has ever shown any link between Red Bull energy drink and harmful effects."