The Bacteria That Half the World Is Carrying Right Now

A common stomach infection carried by half the world’s population may be quietly draining your vitamin B12 — and most doctors aren’t connecting the two.

Quick Take

Helicobacter pylori (H. pylori) infection is linked to vitamin B12 deficiency in multiple peer-reviewed studies, with one showing 37.6% of infected patients were B12-deficient versus zero percent in uninfected controls.
In some patients, simply treating the H. pylori infection — with no B12 supplements — corrected their anemia and raised their B12 levels.
The bacteria may trigger the immune system to attack the stomach cells that make the protein needed to absorb B12 in the first place.
The science is real but not settled — studies show high variation in results, and not every infected person develops a deficiency.

The Stomach Bug Silently Draining Your B12

H. pylori is not a rare or exotic pathogen. About half the world’s population carries it, often without knowing. It lives in the stomach lining, sometimes for decades, quietly inflaming tissue and disrupting the stomach’s chemistry. Most people associate it with ulcers. Fewer know it may also be robbing them of one of the most critical vitamins for brain and nerve function.

Vitamin B12 is not optional. Your body needs it to make red blood cells, protect nerve fibers, and keep your brain working properly. You cannot make it yourself. You have to absorb it from food — and that process depends entirely on a healthy stomach. That is exactly where H. pylori causes damage.

How H. Pylori Shuts Down B12 Absorption

Your stomach makes a protein called intrinsic factor. Without it, B12 from food cannot be absorbed into your bloodstream. H. pylori attacks the stomach cells that produce this protein. Research shows the bacteria can trigger your immune system to produce antibodies that target those same cells — a process called molecular mimicry, where the infection tricks your body into attacking itself. The result is less intrinsic factor, less acid, and less B12 getting through.

A 2024 study found that 37.6% of H. pylori-positive patients had B12 deficiency, compared to zero percent in the uninfected control group — a statistically significant gap. A separate meta-analysis confirmed that H. pylori-positive patients consistently showed lower B12 levels than uninfected patients, and that those levels rose after the infection was treated.

When Treating the Infection Fixed the Deficiency

The most striking finding in this body of research is not the association — it is what happened when the infection was cleared. A Journal of the American Medical Association Internal Medicine study tracked 138 patients with B12 deficiency who also tested positive for H. pylori. Doctors treated the infection and gave no B12 supplements. In 40% of those patients, B12 levels improved and anemia resolved on their own. That is not a small number. That is four in ten people whose B12 problem went away when the stomach infection went away.

A published case report adds weight to that finding. A 23-year-old man developed severe nerve damage — a condition called subacute combined degeneration of the spinal cord — traced directly to B12 deficiency caused by H. pylori. His body had produced antibodies against his own intrinsic factor. Doctors treated the infection. His B12 levels recovered. This is not a theoretical risk. It is a documented, reversible outcome.

What the Science Still Cannot Confirm

Honest reporting requires noting where the evidence gets complicated. The same JAMA Internal Medicine study that showed 40% improvement explicitly stated there was “no sufficient evidence to propose a causal relationship.” That 40% figure also means 60% of infected, B12-deficient patients did not improve after eradication — suggesting other causes were at work in the majority. Some studies find no meaningful link at all between H. pylori status and B12 levels. The 2021 meta-analysis found significant variation across studies and confirmed publication bias, meaning positive findings were more likely to get published than negative ones.

Why This Connection Gets Missed in the Doctor’s Office

H. pylori symptoms mimic acid reflux. Millions of patients get prescribed acid-blocking drugs called proton pump inhibitors (PPIs) instead of being tested for the underlying infection. Those same drugs can reduce the accuracy of H. pylori tests, making the infection harder to detect. Meanwhile, B12 deficiency gets treated with supplements — which helps the symptom but never addresses the root cause. This cycle of misdiagnosis is not a conspiracy. It is a predictable outcome when busy clinicians match symptoms to the most common diagnosis without digging deeper.

The practical takeaway is straightforward. If you have unexplained fatigue, nerve tingling, memory fog, or anemia — and especially if you have been told you have low B12 — ask your doctor to test you for H. pylori. The test is simple. The treatment is a short course of antibiotics. And for a meaningful portion of people, that may be all it takes to get their B12 back on track without a lifetime of supplements.