Wild theories have circulated for years about what caused movie legend Bruce Lee’s untimely death – and now, doctors believe they’ve finally figured it out.

Doctors believe they have discovered the mystery behind the brain swelling that caused Bruce Lee’s death.

The legendary martial artist and actor died in Hong Kong on July 20, 1973, at the age of 32 from brain swelling – from what doctors now say was caused by drinking too much water

“We propose that the kidney’s inability to excrete excess water killed Bruce Lee,” researchers write in the upcoming issue of Clinical Kidney Journal.

“Ironically, Lee made famous the quote, ‘Be water, my friend’ – but excess water appears to have ultimately killed him.”

At the time, doctors believed the brain swelling was due to a painkiller, but nearly 50 years after the Enter The Dragon icon’s death, research shows he likely died of hyponatraemia

Hyponatraemia – a low concentration of sodium in blood, which can be caused by too much water or fluid in the body, according to the Mayo Clinic.

Bruce Lee died from a specific form of kidney dysfunction: The inability to excrete enough water to maintain water homeostasis, which is mainly a tubular function

There were rumours that he was assassinated by gangsters, poisoned by a jealous lover, the victim of a curse and died from heatstroke.

The scientists make the case that Lee had multiple risk factors for hyponatraemia, including high liquid intake, factors that could increase thirst such as marijuana usage,

and factors that debilitate the kidneys’ ability to excrete water such as use of prescription drugs, alcohol, past history of kidney injury or low solute intake.