decided to take a risk.

Too many of his patients were complaining of severe abdominal pain

due to stomach ulcers,

which are sores in the lining of the upper intestinal tract.

At the time, few effective treatments for ulcers existed,

and many sufferers required hospitalization or even surgery.

Desperate for answers,

Dr. Marshall swallowed a cloudy broth of bacteria

collected from the stomach of one of his patients.

Soon, Dr. Marshall was experiencing the same abdominal pain,

bloating,

and vomiting.

Ten days later, a camera called an endoscope

peered inside his insides.

Marshall's stomach was teeming with the same bacteria as his patient.

He'd also developed gastritis, or severe inflammation of the stomach,

the hallmark precursor of ulcers.

Dr. Marshall's idea challenged

a misconception that still persists to this day:

that ulcers are caused by stress,

food,

or too much stomach acid.

Marshall thought the culprit was bacterial infections.

Initially, his idea was considered crazy

by the brightest medical minds on the planet.

But in 2005, he and Dr. Robin Warren received the ultimate validation

when they were awarded the Nobel Prize for medicine.

Our stomachs are J-shaped organs with surprisingly intricate ecosystems

awash in hormones and chemicals.

The stomach is under constant attack by digestive enzymes,

bile,

proteins,

microbes,

and the stomach's own acid.

In response, it produces bicarbonate,

mucus,

and phospholipids called prostaglandins

to maintain the integrity of its own lining.

This delicate balance is constantly regulated

and referred to as mucosal defense.

Since the mid-1800s, doctors thought stress alone caused most stomach ulcers.

Patients were given antidepressants or tranquilizers

and told to visit health spas.

This belief eventually shifted to the related notion of spicy foods

and stress as culprits.

Yet no convincing study has ever demonstrated that emotional upset,

psychological distress,

or spicy food

directly causes ulcer disease.

By the mid-20th century, it was widely accepted that excess hydrochloric acid

prompted the stomach to eat itself.

Fervent proponents of this idea were referred to as the acid mafia.

The biggest hole in this theory was that antiacids only provide

temporary relief.

We now know that some rare ulcers

are indeed caused by too much hydrochloric acid.

But they make up less than 1% of all cases.

Dr. Marshall and Dr. Warren pinpointed a spiral-shaped bacteria

called Helicobacter pylori, or H. pylori, as the real offender.

H. pylori is one of humanity's oldest and most frequent companions,

having joined us at least 50,000 years ago,

and now found in 50% of people.

Previously, we thought the stomach was sterile

on account of it being such an acidic, hostile environment.

Yet H. pylori survives the acidic turmoil of the stomach

with a variety of features that disrupt mucosal defense in its favor.

For example, it produces an enzyme called urease

that helps protect it from the surrounding gastric acid.

H. pylori can make over 1,500 proteins,

many of which are dedicated to maximizing its virulence.

We still have unanswered questions,

like why specific people develop ulcers at particular times.

However, we do know individual genetics,

other medical problems,

use of certain medications,

smoking,

and the genetic diversity of Helicobacter strains all play a role.

In particular, certain pain medications used to reduce inflammation in joints

have been discovered to work with H. pylori

to create more severe stomach ulcers.

Dr. Marshall ended up being fine after his famous, albeit dangerous, experiment.

He ingested a course of antibiotics similar to the ones taken now for ulcers.

To be treated by simple antibiotics is a modern triumph

for a disease that previously needed surgery.

Marshall's work also reminded us that scientific progress is not always smooth.

But there's value in trusting your proverbial,

and sometimes literal, gut.