Brian Johnson, a technology entrepreneur and longevity enthusiast, has revealed that he has been diagnosed with autoimmune gastritis (AIG). Sharing the news on X (formerly Twitter), he wrote: “My stomach is eating itself.” He also said that almost “2-5% of people have it too. Probably more because it’s hidden.” He explained that despite years of regular medical examinations, the disease remained hidden until a gastric biopsy confirmed the diagnosis. According to Johnson, he had been experiencing low iron levels for more than a decade, but the underlying cause had not been identified because AIH often develops silently, without obvious symptoms. He also reported that he had previously been diagnosed with an autoimmune thyroid disease, suggesting that multiple autoimmune diseases can occur simultaneously. Johnson said his current medical care is more focused on fighting the disease.
In his post, he described how his team investigated several possible reasons for his persistent iron deficiency before finally discovering the real cause through endoscopy and biopsy. He also noted that autoimmune gastritis can affect 2% to 5% of people and may be more common because it is difficult to diagnose in the early stages. In his post, the 48-year-old wrote: “We now have an official diagnosis. I have autoimmune gastritis AIH. My stomach eats itself.
“So it was never just one problem. There were three of them, related to each other: iron deficiency, its causative autoimmune gastritis, and concomitant autoimmune thyroid disease.”
Bad news #1:
I have an autoimmune disease. My stomach eats itself.
Bad news #2:
2–5% of people have this too. Probably more because it’s hidden.
Good news:
I’ll try to solve this problem. I’ll share everything.
As a child, I ate sugary cereal, drank soda, and ate… pic.twitter.com/EbJ8a916uS
— Bryan Johnson (@bryan_johnson) June 30, 2026
What is autoimmune gastritis?
Autoimmune gastritis (AIG) is an autoimmune disease in which the body’s immune system mistakenly attacks its own stomach cells, especially acid-producing cells. Over time, this damages the stomach lining, reduces stomach acid production, and affects the body’s ability to absorb important nutrients such as vitamin B12 and iron. As the disease progresses, it can lead to chronic inflammation, atrophy of the stomach lining, anemia and, in some cases, an increased risk of stomach cancer. The disease often develops slowly and can go undetected for many years because many people have few or no symptoms in the early stages.
Symptoms of autoimmune gastritis
Symptoms of AIH can vary from person to person. Some people have no symptoms at all, while others develop signs related to vitamin and mineral deficiencies rather than stomach problems.
Common symptoms include:
- Constant fatigue or weakness
- Low iron levels or iron deficiency anemia.
- Vitamin B12 deficiency
- Numbness or tingling in the arms and legs
- Difficulty concentrating or memory problems.
- Nausea, bloating, or mild stomach discomfort.
- Loss of appetite
- Pale skin or shortness of breath due to anemia.
Because these symptoms are common with many other conditions, diagnosing this condition can be challenging.
Who is at risk of developing the disease?
Doctors don’t know the exact cause of autoimmune gastritis, but there are several factors that can increase your risk of developing AIH.
- People with other autoimmune diseases, such as autoimmune thyroid disease, type 1 diabetes, or vitiligo.
- Family history of autoimmune diseases may increase risk
- Women and older people
How is it diagnosed and treated?
There is no single test to confirm autoimmune gastritis. Doctors usually rely on a combination of blood tests, vitamin B12 and iron levels, antibody testing, endoscopy and stomach biopsies. Johnson tweeted that his diagnosis was only confirmed after biopsy samples were analyzed, despite years of regular follow-up.
Although there is currently no cure for AIH, treatment is aimed at reversing its effects and preventing complications. Patients may require vitamin B12 injections or supplements, iron therapy if iron deficiency is present, and regular monitoring to detect changes in the gastric lining.
Is it possible to prevent autoimmune gastritis?
There is no proven way to prevent autoimmune gastritis as it is an autoimmune disease. However, early diagnosis can help reduce complications. People with persistent iron deficiency, unexplained anemia, or other autoimmune diseases should discuss testing options with their healthcare provider.
Disclaimer: This content, including advice, provides general information only. It is in no way a substitute for qualified medical opinion. Always consult a specialist or your doctor for more information. NDTV is not responsible for this information.