If you’ve ever had a stomach ulcer or gastroesophageal reflux disease, a well-meaning friend or relative has probably told you to relax and watch what you eat. Stomach acid, triggered by stress or spicy food, is popularly thought of as the root cause. The history of how this belief was disproved tells us much about evidence, theories and scientific consensus.
In 1962, Thomas Kuhn popularised the concept of the paradigm shift. Kuhn claimed science does not make progress by gradually accumulating new knowledge and rejected the idea of objective scientific truth. Instead, Kuhn argued that science is based on models, or paradigms, that reflect scientific consensus. Within this framework, scientists do “normal science”, day-to-day research that fills in gaps in understanding.
Although this allows incremental progress, eventually it produces anomalous results and when the possibilities of explaining these within the paradigm are exhausted, they must look outside for answers. If these new explanations are successful, they will lead to the adoption of a new paradigm – a paradigm shift. A good example is the Copernican revolution.
Medieval European astronomy was based on a geocentric model in which the sun and stars orbited Earth. Astronomers had expended considerable effort attempting to explain why the observable movement of the planets did not fit within this paradigm. Eventually, the Polish scholar Nicolaus Copernicus devised a new model that better explained how the stars moved: the heliocentric model in which Earth and the other planets orbit the sun.
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Spiral-shaped bacteria
When Barry Marshall joined the Royal Perth Hospital, Western Australia, in 1979, he began a fellowship in internal medicine and became interested in gastric symptoms. At the time, the dominant paradigm was that gastritis, ulcers and similar illnesses were caused by stomach acid. But after meeting pathologist Robin Warren in 1981, Marshall became convinced that excess acid was not the cause. When conducting autopsies, Warren had noticed that some stomachs contained unusual spiral-shaped bacteria. By coincidence, Marshall had recently treated a patient with unexplained abdominal pain and a stomach biopsy had identified unusually shaped bacteria.
After studying the bacteria, Marshall and Warren hypothesised that it was responsible for gastric ulcers. Examining the biopsies of ulcer patients at the hospital showed that the majority were infected with the bacteria. After collaborating with international colleagues, they were able to identify a substantial number of cases in which ulcer biopsies contained the spiral bacteria. A study that they carried out on 100 patients found the bacteria in the majority of patients with gastric ulcers and in all of the patients with duodenal ulcers.
Although many microbiologists were convinced by their discovery, Marshall and Warren had less success convincing the wider medical community. Much time, effort and money had been expended on treating excess acid. In the 1970s, pharmacists had developed cimetidine, the first of a new class of drugs called H2 receptor antagonists that blocked the cells of the stomach from producing acid.
The sceptics
A new drug of the same class, ranitidine, had just been approved. Another class of drugs called protein pump inhibitors, which were even more effective at blocking acid production, were undergoing human trials. Another problem was that the acidic environment of the human stomach was generally inhospitable to bacteria.
To convince the sceptics, Marshall and Warren had to demonstrate that the bacteria caused ulcers. After much effort, they had been able to cultivate the bacteria in the laboratory. But because it was primarily adapted to primates, they were unable to demonstrate its effect in lab mice. Deliberately infecting humans with a pathogen was unlikely to be approved by an ethics committee, and so Marshall, a consummate showman, chose to experiment on himself.
After an examination to demonstrate that he had no infection from the bacteria or gastric upset, he swallowed a beaker of the bacteria. Several days later he experienced severe stomach upset alongside a positive bacterial culture, commenced a course of antibiotics and recovered fully.
Treatment for gastritis and stomach ulcers moved from combating acid to eliminating the bacteria, which became known as Helicobacter pylori. The standard treatment now includes antibiotics. And although Marshall and Warren had struggled to change scientific consensus, they eventually caused a paradigm shift. They were awarded the Nobel Prize for their discovery in 2005. And if you have gastritis, you can probably still enjoy a curry.
Stuart Mathieson is a postdoctoral fellow in the school of history and geography at Dublin City University