A 30-year-old 2012 London Marathon participant who collapsed and died a mile before the finish line is said to have had a banned energy drink in her water bottle.

Authorities are now saying that Claire Squires had Jack3d in her water bottle during the race. While it is unknown whether or not she drank it as planned after mile 15, doctors believe that it could have contributed to her death.

Prof. William McKenna of the University College London hospitals trust, who reviewed Squires' medical records, said he found "significant levels" of the amphetamine-like substance in her blood. The energy drink was, he added, "an important factor" in Squires' death.

"In an apparently fit and healthy young woman who dies suddenly in the last stages of the London Marathon, with no abnormalities identified to explain her death, the toxicology identifying an amphetamine-like substance does suggest its contribution to her [cardiac] arrest, particularly after excessive exercise," he said. "In the absence of further evidence, we think the irregular heartbeat is a red herring and the substance found in the blood is an important factor in the outcome."

Jack3d was banned in the United Kingdom in August—four months after the London Marathon—after its key ingredient, DMAA (dimehtylamylamine), was linked to high blood pressure, headaches, vomiting, stroke, and a death. Similar rulings have been issued in the U.S. and Australia.

DMAA is a stimulant similar to amphetamines and its use in Jack3d was said to boost energy, concentration, and metabolism. Squires told her boyfriend she wanted to take it in order to beat her previous marathon time.

Via The Guardian