For more than a century, doctors believed they understood the cause of stomach ulcers: stress. But in the 1980s, one Australian doctor dared to challenge that concept, and he put his own stomach on the line to prove it.

“It was such a tradition of believing that stress cause ulcers, really going back for nearly 100 years, that nobody questioned it anymore,” Dr. Barry Marshall, a Nobel Laureate and medical microbiologist at the University of Western Australia, told Motherboard’s postcast Science Solved It. “Nobody really could tell where this evidence had come from and, in fact, there were a few experiments on different things which were never repeated and probably could never be repeated because they were just a one off. But they're written up in such a way that it fitted in with everyone's concept and so on it went.”

In 1981, Marshall was in his third year of an internal medicine fellowship and had been working with Dr. Robin Warren, the chief pathologist at the Royal Perth Hospital. Warren suggested he take a look at an odd pattern he had noticed: fellow physicians had sent him patients with particularly troublesome ulcers, and they all had an infestation of a particular bacteria living in their gut called Helicobacter pylori.

Marshall suspected that maybe the bacteria had something to do with developing ulcers, so he cultured the bacteria, and started doing experiments. He started with mice and pig models, but wasn’t able to get the animals to pick up the infection at all, which made it impossible to see if it was related to ulcers. What was worse, the medical community dismissed the idea that there was even a chance the bacteria caused ulcers.

After having success with a small handful of patients whom he treated for the bacterial infection, Marshall decided to take matters into his own hands—really, his own stomach.

“I brewed up the bacteria in petri dishes and put it into roast beef soup and then I drank the bacteria,” Marshall said.

Within five days, he was vomiting due to the bacterial infection, and had an endoscopy done, showing that he had developed both a bacterial infection and stomach inflammation—the first step toward getting an ulcer. It took almost a decade of further research, but eventually the medical community embraced Marshall’s findings and started to test ulcer patients for H. pylori, and treating them with simple antibiotics if they had the infection. In 2005, Marshall and Warren won the Nobel Prize in medicine for their discovery. Their research has saved lives, as chronic stomach ulcer sufferers are at a greater risk of developing stomach cancer.

But it was only possible thanks to Marshall’s decision to gulp back a hearty shot of bacteria stew.