Bryan Johnson Says His "Stomach Is Eating Itself" — Here's What Autoimmune Gastritis Is

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Bryan Johnson has spent close to $2 million a year and enlisted a team of over 30 doctors trying to out-test ageing itself. Last week, all that testing caught something none of it was built to look for. Biopsies confirmed early autoimmune gastritis - a condition in which the immune system attacks and slowly erodes the stomach's acid-producing lining.

Photo Credit: Facebook: @BryanJohnson

Johnson broke the news himself, writing that his stomach "is eating itself" and that the condition affects an estimated 2-5% of people, likely more, because it hides. The trail that led there started with something almost boringly common: low ferritin, the blood marker for stored iron.

The Clue Hiding In A Routine Blood Test

Bad news #1:

I have an autoimmune disease. My stomach is eating itself.

Bad news #2:

2–5% of people have this, too. Likely more, because it hides.

Good news:

Im going to try and solve it. Will share all.

As a kid, I ate sugar cereal, drank sugary soda, and gobbled down… pic.twitter.com/EbJ8a916uS

— Bryan Johnson (@bryan_johnson) June 30, 2026

For years, doctors have treated low ferritin as something to top up with a supplement and move on from. Johnson's case argues otherwise. His team traced the low iron back to autoimmune gastritis, which was in turn linked to an autoimmune thyroid condition - each one quietly making the other harder to fix.

This isn't a fringe finding. Research published in Acta Haematologica has found that 20 to 27% of people with unexplained iron deficiency anaemia turn out to have autoimmune gastritis once properly investigated - a number gastroenterologists have flagged as significantly under-recognised in everyday practice. A separate review notes that patients with chronic iron deficiency, especially those who don't respond to oral iron, should be evaluated for autoimmune gastritis specifically.

The disease is easy to miss because it rarely announces itself with stomach pain. Roughly half of patients with autoimmune gastritis report no upper gastrointestinal symptoms at all, which is exactly why an endoscopy alone can look normal unless biopsies are specifically taken from the stomach's acid-producing region.

Why This Isn't Just A Biohacker's Problem

The scale of underdiagnosis is the real story here. In one study of patients with precancerous stomach changes, researchers found an 18% prevalence of autoimmune gastritis antibodies compared to 7% in healthy controls - yet only three of the 256 patients tested had ever previously been diagnosed with the condition.

Left unchecked over years, the same clinical review notes that the condition can progress to vitamin B12 deficiency, anaemia, and a measurably increased risk of gastric neuroendocrine tumours and stomach cancer - which is why international guidelines recommend endoscopic surveillance once it's confirmed.

Johnson, never one to undersell a health lesson, put it simply.

"The absence of symptoms is not the presence of health." - Bryan Johnson, founder, Project Blueprint

It's a line built for his brand, but the underlying point holds regardless of anyone's views on his $2-million protocol: a "normal" endoscopy or a single low-iron reading isn't the same as a clean bill of health, particularly when the deficiency keeps coming back.

What This Means If Your Iron Levels Won't Budge

For most people, this isn't cause for alarm - autoimmune gastritis is treatable once caught, mainly through iron and B12 replacement and periodic monitoring. But it is a reason to ask more questions if:

• Iron or ferritin levels stay low despite months of supplementation
• You have an existing autoimmune thyroid condition (the two are known to overlap)
• Unexplained fatigue, hair thinning, or pallor persists alongside "normal" scans
• A doctor hasn't specifically tested for parietal cell or intrinsic factor antibodies

None of this requires a 100-biomarker panel. It requires asking a doctor one specific question: could this iron deficiency have a cause we haven't ruled out yet.

Disclaimer: The information provided in this article is for general informational and educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or a qualified healthcare provider with any questions you may have regarding a medical condition.