A MAN has died from a caffeine overdose after eating energy mints bought at his local store.

The body of John Jackson, 40, was discovered by family members after he ate Hero Instant Energy Mints, a brand of sweets containing high concentrations of caffeine.

A post-mortem examination showed Mr Jackson had 155mg of caffeine per litre of blood in his system, Sky News reported. Just 10mg is considered an overdose.

"This is a potentially very dangerous situation,” Coroner Robin Balmain told an inquest in Smethwick, in western England. “The level of caffeine is enormous. I think it's as certain as it can be that Mr Jackson didn't know that he was going to expose himself to this sort of danger."

A pathologist gave the cause of death as caffeine toxicity, but added that Mr Jackson had cirrhosis of the liver - a result of heavy drinking - which would have made it harder for him to absorb the stimulant properly.

Just one of the sweets is believed to have more caffeine than a whole can of high-energy drinks like Red Bull.

The makers of the sweets, Hero Energy Ltd, said they had taken steps to warn about the high caffeine content, including advisories on the packaging, websites, and shelf displays, telling consumers not to eat more than five mints in 24 hours.

However, Mr Jackson’s stepdaughter Rebecca Court, 23, said the easy availability of the mints represented a potential threat to the public.

"A kid could go in and buy them and the same thing could happen to him," Sky reported Miss Court as saying.