This article originally appeared in the February 2006 Harvard Health Letter and is provided courtesy of Harvard Health Publications.

H. pylori: Does it have a silver lining?

The bacterium is a leading cause of ulcers, but it might have health benefits, too.

The discovery of the ulcer-causing stomach bug Helicobacter pylori (H. pylori) was a triumph of scientific inquiry. But it also speaks to the uncertainties and complications of scientific inquiry.

Australian researchers J. Robin Warren and Barry J. Marshall proved that the curvy bacterium caused inflammation in the stomach (gastritis) and ulcers in the stomach and upper part of the small intestine (duodenum). Marshall famously drank a glass of the bug to help make the case. When the pair announced their findings, they were, in effect, laughed off the lectern. Everyone then believed that stress was the main cause of ulcers, and that bacteria couldn’t survive the stomach’s acid environment. But the researchers persevered; the tide turned; and the medical community recognized their findings.

Around the world, H. pylori is the major cause of ulcers in the stomach and duodenum. When Marshall discovered that the bacterium produces the enzyme urease (pronounced YOUR-?-ace), he developed a urea breath test for the infection. The test is simple, noninvasive, and accurate, and remains a common way of diagnosing the infection, along with blood and stool tests. Once diagnosed, patients can be treated with new antibiotic therapies that eliminate the bacteria.

H. pylori isn’t the only cause of ulcers. Nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin, ibuprofen (Motrin, other brands), and naproxen (Aleve, other brands) are the second leading cause in developed countries. Alcohol and smoking are risk factors.
Other culprits include gastrointestinal illnesses like Crohn’s disease (an inflammatory bowel condition) and Zollinger-Ellison syndrome (a tumor of the pancreas and upper part of the small intestine that increases stomach acid production).

Stamp it out?
No one is advocating eradication of H. pylori, and infections aren’t treated unless they are causing problems for the patient. Roughly 40%–50% of the world’s population is infected with the bug, although it’s much less in many industrialized nations, probably because of improved hygiene and antibiotics. As a result, H. pylori is responsible for a smaller proportion of ulcers in the United States and many other countries. It is often a rather unobtrusive guest, causing no symptoms and doing no harm. Only 10%–15% of infections lead to ulcers.

Eradication would also exacerbate the problem of antibiotic resistance. Clinicians have already encountered H. pylori strains that aren’t fazed by “triple therapy,” which combines two antibiotics — commonly amoxicillin and clarithromycin — with omeprazole (Prilosec) or a similar drug to counter stomach acid.

Studies in Austria and Japan have shown the prevalence of resistant strains doubling in just two to four years.

So what’s the up side?
Strangely, some research suggests that H. pylori may actually do some good.

NSAID-related ulcers. The prevailing view is that H. pylori increases the risk of developing an ulcer from NSAIDs. But Polish researchers have found quite the opposite — that infection may limit the damage done by NSAIDs. The gastric response to H. pylori is varied, so it’s conceivable that the bacterium protects some stomachs, but not others.

GERD. Some experts contend that H. pylori could lessen the damage from gastroesophageal reflux disease (GERD), the regurgitation of stomach contents into the esophagus and an important risk factor for esophageal cancer. H. pylori survives, in part, by producing urease, which breaks down into ammonia, a compound that helps neutralize stomach acid.

One study showed a 14% increase in patients’ stomach acid after H. pylori eradication, which is perhaps enough to worsen esophageal damage.

Obesity. The same researchers linked the falling rate of H. pylori infection to our current obesity crisis. They focused on ghrelin (GRELL-in), a peptide in the stomach that helps increase appetite and food consumption. It turns out that eliminating H. pylori boosts ghrelin levels by 75%.

It’s not surprising that H. pylori may have some benefits. Its worldwide prevalence and specialized adaptations suggest that it “co-evolved” with humans over a great span of time. It makes sense that the relationship could feature some symbiotic elements. In discussing “microflora” — microorganisms that view us as prime real estate — it’s tempting to distinguish “good bugs” from “bad bugs.” But with microorganisms, you can’t always tell the white hats from the black. “In a world of black and white,” researcher Martin J. Blaser has observed, “Helicobacter pylori is gray.” And recognizing that complexity is also a part of scientific inquiry.