Bryan Johnson has shared that he has been diagnosed with autoimmune gastritis, an incurable condition that can quietly damage the stomach lining and lead to nutrient deficiencies if it is not monitored and treated.
The 48-year-old entrepreneur said on social media that he has autoimmune gastritis, also known as AIG. The condition is considered uncommon, but estimates vary, and recent reviews suggest it may be more common than many people realize.
Johnson, who moved from tech into the biohacking world, has become one of the best-known names in the longevity space.
He is widely known for spending huge sums each year on a strict anti-ageing routine designed to slow, and potentially reverse, the effects of growing older.
Even with that intense focus on health, he has now confirmed the diagnosis and is urging others to pay attention to possible symptoms and to get screened if they are at higher risk.
He explained that after years dealing with stress, weight gain and long-term depression, his body developed an autoimmune response that affected both his thyroid and the lining of his stomach. He also admitted he tried to ‘solve’ the issue himself.
Johnson said he had not noticed any clear symptoms at first, but now believes there were likely earlier signs of AIG that went unrecognized.
He is far from the only person to miss the signs, as autoimmune gastritis can be “silent” for years. Early on, it may cause few or no symptoms. When symptoms do appear, they can include abdominal discomfort, bloating, nausea, loss of appetite, unexplained weight loss, fatigue, iron deficiency and vitamin B12 deficiency.
Because the disease can develop gradually, it is often picked up only after blood tests or an endoscopy for another reason. Doctors may also look for markers such as anti-parietal cell antibodies, intrinsic factor antibodies, low ferritin or iron, low B12, elevated gastrin and elevated chromogranin A, depending on the stage of disease.
After Johnson underwent a colonoscopy that ruled out colon cancer, his doctors carried out a bidirectional endoscopy to examine the rest of his gastrointestinal tract.
Those tests found elevated anti-parietal-cells-antibodies levels, leading his medical team to investigate autoimmune gastritis more closely.
Although there is no cure for AIG, it can be treated and monitored with measures such as B12 injections, iron supplementation or iron infusions, and periodic endoscopic surveillance in some patients because of the long-term risk of complications. Johnson recently said he received a “1,000 mg Monoferric iron infusion”.
His team plans ongoing checks on several markers, including ferritin and iron, B12, gastrin and chromogranin A.
The Mayo Clinic writes: “This type of gastritis occurs when your body attacks the cells that make up your stomach lining. This reaction can wear away at your stomach’s protective barrier.”
The Cleveland Clinic says some people may have a greater likelihood of developing the condition than others.
Autoimmune gastritis is more likely in people who already have other autoimmune diseases, including autoimmune thyroid disease, type 1 diabetes, vitiligo or pernicious anemia. Experts also note that it can increase the risk of iron deficiency, vitamin B12 deficiency, pernicious anemia and, in some cases, gastric neuroendocrine tumours or stomach cancer, which is why follow-up matters even when symptoms are mild.
Writing on X, Johnson said: “Current medical standards treat AIG as something to be managed, not resolved.
“We want to change that.”