LONDON (AP) -- A London Marathon runner whose death inspired more than $1 million in donations took a dietary supplement that may have contributed to her heart failure, a coroner ruled Wednesday.
Claire Squires collapsed near Buckingham Palace last April near the end of the marathon. She was running to raise money for an organization that helps prevent suicides.
According to an inquest at Southwark Coroner's Court, the 30-year-old runner's water bottle included a scoop of the supplement Jack3D, which contains a stimulant called DMAA or dimethylamylamine.
DMAA is on the list of substances prohibited by the World Anti-Doping Agency, but Jack3D was legally available to buy in Britain before being banned in August because of potential risks to public safety.
"DMAA ... on the balance of probabilities, in combination with extreme physical exertion, caused acute cardiac failure, which resulted in her death," coroner Philip Barlow said.
The substance was bought legally online. It is on the list of substances prohibited by the World Anti-Doping Agency.
Marathon organizers are assessing changes to the advice given to recreational runners about the use of supplements.
"The substance is on the (WADA) banned list, but the only athletes to be tested would be elite athletes," London Marathon spokeswoman Nicola Okey told The Associated Press. "We just ask the rest of the runners to be medically fit. We don't make any other inquiries about what substances they are taking.
"We will be amending our medical advice following the inquest's verdict. We obviously give medical advice, but it hasn't mentioned before the use of supplements."
Britain's Medicines and Healthcare products Regulatory Agency in August ruled that Jack3D must "be removed from the UK market amid concerns of potential risks to public safety," highlighting that people are suspected to have had shortness of breath and heart attacks after using it.
But Jack3D's manufacturer, Ultra-Premium Supplements, on Wednesday defended the safety of its product.
"USPlabs sympathizes with the family of Ms. Squires for their tragic loss," the Dallas-based company said in a statement emailed by London publicists. "We continue to stand by the safety of the dietary ingredient 1, 3 DMAA. The ingredient has been the subject of seven clinical trials supporting its safety when used as directed. These studies place 1,3 DMAA among the most studied dietary ingredients on the market."