Longevity entrepreneur Bryan Johnson revealed that he has been diagnosed with autoimmune gastritis (AIG)—a chronic autoimmune disease that slowly damages the stomach lining.

Sharing the news on X, Johnson wrote, “My stomach is eating itself,” describing his determination to help find better treatments for a condition that currently has no cure.His announcement has drawn attention to a little-known disease that often develops quietly for years before it is discovered.

What Is Autoimmune Gastritis and Why Is It Often Missed?

Autoimmune gastritis is a chronic condition in which the body’s immune system mistakenly attacks the parietal cells of the stomach. These specialized cells produce hydrochloric acid and a protein called intrinsic factor, both of which are essential for proper digestion and vitamin B12 absorption.

Unlike H. pylori gastritis, which is caused by bacterial infection, autoimmune gastritis results from an abnormal immune response.

Studies estimate that 0.5% to 2% of people in the United States may have autoimmune gastritis, but many remain undiagnosed because symptoms can be absent or extremely mild.

The Real Problem: Iron Deficiency May Be the First Warning Sign

Johnson explained that doctors discovered his condition only after years of persistently low ferritin levels, a marker of the body’s iron stores.

Despite improving his diet and taking iron supplements, his ferritin levels remained low. Surprisingly, he had no anemia and no obvious symptoms.

Only after undergoing detailed investigations—including blood tests, an upper gastrointestinal endoscopy, and stomach biopsies—did doctors identify autoimmune gastritis.

This case highlights an important medical lesson: persistent iron deficiency without an obvious cause should never be ignored, even when routine blood counts appear normal.

According to gastroenterologists, autoimmune gastritis should be considered in patients with unexplained iron deficiency because the disease may silently damage the stomach long before anemia develops.

Why This Disease Can Stay Hidden for Years

One of the biggest challenges with autoimmune gastritis is that most patients experience few, if any, noticeable symptoms during the early stages.

When symptoms do appear, they are often vague and may include:

Ongoing fatigue
Reduced stamina
Difficulty concentrating
Indigestion
General weakness
Feeling “not quite right”

Because these complaints are common to many other conditions, diagnosis is frequently delayed.As stomach damage progresses, patients may develop deficiencies of iron and vitamin B12, leading to anemia or neurological symptoms such as numbness, tingling, or balance problems.

Why Iron Supplements Alone Are Not Enough for Bryan Johnson

Many people assume that taking iron tablets will solve iron deficiency.

However, in autoimmune gastritis, supplements treat only the deficiency—not the underlying autoimmune attack damaging the stomach.

Doctors instead focus on:

Correcting iron deficiency

Replacing vitamin B12 when needed

Monitoring stomach health over time

Detecting complications early through periodic endoscopy

Experts sometimes recommend endoscopic surveillance every 2 to 5 years because long-term autoimmune gastritis carries a small increased risk of stomach cancer. Recent research estimates that approximately 0.12% of patients with autoimmune gastritis develop gastric cancer each year, with risk increasing in advanced disease.

Bryan Johnson Shares Experimental Plan to Treat Autoimmune Gastritis

Instead of relying on conventional care, Bryan Johnson is working on a precision medicine strategy aimed at identifying and stopping the immune cells responsible for the disease.

His plan includes:

Mapping one million immune cells to identify the specific T-cells attacking his stomach.

Collecting a second live stomach biopsy to match rogue immune cells with damaged tissue.

Monitoring disease activity through blood tests every two weeks alongside wearable health data to detect silent flare-ups.

Creating a lab model of his immune system by preserving immune cells, allowing researchers to test experimental treatments before using them in his body.

Developing targeted therapies that disable only the harmful immune cells while leaving healthy immune function intact.

Before any treatment is used, Bryan Johnson plans to validate it using computer simulations and laboratory testing on his own preserved cells to maximize safety.

What Medical Experts Say

Gastroenterologists emphasize that Bryan Johnson’s diagnosis should not create unnecessary fear.Although autoimmune gastritis is incurable, many patients live normal lives with proper monitoring and treatment of nutritional deficiencies.

Experts also point out that the disease is rarely life-threatening and is frequently discovered only by chance during investigations for unexplained iron deficiency or vitamin B12 deficiency.

Maintaining a balanced diet, exercising regularly, managing stress, and attending follow-up appointments can help support overall health, although these measures do not cure the disease.

Bryan Johnson’s diagnosis has brought attention to a condition that many people—and even some patients receiving regular healthcare—may not know they have.

Bryan Johnson’s case serves as a reminder that persistent low ferritin levels should not always be attributed to diet alone. Sometimes they may signal an underlying autoimmune condition that quietly damages the stomach over many years.

While there is currently no cure for autoimmune gastritis, early diagnosis allows doctors to replace missing nutrients, monitor for complications, and help patients maintain a good quality of life.

As research continues, scientists hope future therapies may one day stop the disease before permanent stomach damage occurs.

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