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Tech entrepreneur and longevity advocate Bryan Johnson has announced that he has been diagnosed with autoimmune gastritis after more than a decade of unexplained low iron stores. Johnson shared the update on social media, writing, "My stomach is eating itself," and said the diagnosis was confirmed in May 2026 following blood tests, an upper gastrointestinal endoscopy, and stomach biopsies.
I have an autoimmune disease. It’s called Autoimmune Gastritis.
Bryan Johnson
Johnson said he had persistently low ferritin levels for about 11 years despite dietary changes and iron supplementation. According to his post, earlier medical evaluations did not identify the underlying cause because he did not have anemia and his hemoglobin levels remained within the normal range.
Ferritin reflects the body's stored iron and can become depleted long before anemia develops, making isolated low ferritin an early sign that warrants further evaluation.
The numbers that define anemia looked fine, so no one asked why my iron reserves wouldn’t refill. During these 11 years, before doing health stuff and when on my longevity protocol, I sadly did not fully understand how important iron was to my body. Now, everywhere I look, I see iron playing a central role.
Bryan Johnson
He said a new medical team carried out additional investigations, including specialized blood tests and endoscopy. The tests reportedly showed elevated anti-parietal cell antibodies, while biopsy samples reportedly confirmed early-stage autoimmune gastritis.
In response to concerns and suggestions from social media users, Johnson shared a post on X,
For those of you suggesting that I eat meat and get sun to cure my autoimmune gastritis, I was eating meat and in the sun for hours a day when this autoimmune condition started. I continued to eat meat and was in the sun as it progressed. And to be clear, I know you’re coming from a good place, and I appreciate your intent.
Bryan Johnson
Although Bryan Johnson now follows a structured diet and exercise regimen, he said he believes the condition may have developed years earlier. In a post on X, he reflected on his childhood eating habits, stating that his diet included sugary cereals, soft drinks, and fast food.
As a kid, I ate sugar cereal, drank sugary soda, and gobbled down fast food. I became a young father of three and began building a business. Juggling that stress and grind, I let my health slip and gained 40 lbs. Within a few years I’d fallen into a deep, chronic depression
Bryan Johnson
Johnson added that he believes it was during this period that his body began developing autoimmune changes. He said the process first affected his thyroid and later his stomach lining. However, he did not claim a direct causal relationship between his earlier lifestyle and the development of the autoimmune condition.
In his social media post, Johnson said he plans to document his medical journey and share updates as he works with his healthcare team to better understand and manage the condition. He also stated that he hopes to contribute to research on autoimmune diseases using data collected during his treatment and monitoring.
What is autoimmune gastritis?
Autoimmune gastritis (AG) is a chronic condition in which the immune system mistakenly attacks the stomach's acid-producing parietal cells. This damage reduces the production of stomach acid and intrinsic factor, which are important for absorbing nutrients such as iron and vitamin B12.
The condition may initially present with iron deficiency and later lead to vitamin B12 deficiency as the loss of intrinsic factor progresses.
What are the early signs of autoimmune gastritis?
Many people do not experience symptoms in the early stages. When symptoms occur, they may include fatigue, weakness, iron deficiency, vitamin B12 deficiency, indigestion, bloating, or abdominal discomfort. Some patients are diagnosed only after routine blood tests reveal low iron or vitamin B12 levels.
How is autoimmune gastritis diagnosed?
AG is usually diagnose autoimmune gastritis using a combination of blood tests, upper gastrointestinal endoscopy, and stomach biopsies. Blood tests may detect antibodies against parietal cells or intrinsic factor, while biopsy findings help confirm the diagnosis.
What complications can autoimmune gastritis cause?
If left untreated, autoimmune gastritis can lead to iron deficiency, vitamin B12 deficiency, pernicious anemia, and neurological complications related to vitamin B12 deficiency. It is also associated with an increased risk of gastric neuroendocrine tumors and gastric adenocarcinoma, making long-term follow-up important for some patients.
Can autoimmune gastritis be treated?
There is currently no cure for autoimmune gastritis. Treatment focuses on correcting iron and vitamin B12 deficiencies, managing symptoms, monitoring for complications, and providing regular follow-up care when indicated.
1. Cleveland Clinic. “Atrophic Gastritis: Symptoms, Treatment, Diet & Definition.” Last reviewed September 25, 2022. Accessed July 8, 2026. https://my.clevelandclinic.org/health/diseases/24217-atrophic-gastritis.
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