Brian Johnson, the millionaire who transformed his body into an extreme anti-aging project, was diagnosed with autoimmune gastritis—a chronic disease that develops over years without clear symptoms and is sometimes revealed only through iron or vitamin B twelve deficiency.

Two experts explain how to diagnose and treat it.

"If there are nutritional deficiencies that cannot be explained by other reasons, it is worth investigating," says Professor Bella Ongar, head of the gastroenterology-immunology service at Sheba Medical Center.

Brian Johnson, the technology entrepreneur and American millionaire who in recent years became one of the prominent symbols of the longevity trend and turned his body into an extreme testing ground, revealed that he was diagnosed with a chronic autoimmune disease affecting the stomach.

"My stomach eats itself," wrote Johnson, forty-eight years old, who is best known for his extreme attempts to slow aging and monitor almost every parameter in his body, in an in-depth post he published on the social network X.

The disease that Johnson was diagnosed with is called autoimmune gastritis, or AIG.

It is a condition where the immune system mistakenly attacks the lining cells of the stomach.

According to Johnson, this is a difficult-to-detect disease that often remains silent for years and can lead to nutritional deficiencies, anemia, and an increased risk of further complications over time.

He stated that the disease affects approximately two to five percent of the population, and possibly more, because it is often undiagnosed.

The exposure generated particular interest because of Johnson's identity, as he had recently built an extreme health project around himself, in which he managed a particularly strict lifestyle: careful diet, exercise, frequent blood tests, sleep monitoring, fertility tracking, medical treatments, and various experiments aimed, according to him, at slowing down the aging process.

Previously, it was reported that he spent millions of dollars annually trying to keep his body in optimal condition.

Now, the person who presents himself as someone seeking to break through the boundaries of preventive medicine reports that a significant disease developed in his body over the years almost without anyone noticing.

In the post he published, Johnson described how his health journey did not always look as it does today.

According to him, in his childhood, he used to eat sugary cereals, drink sweetened beverages, and eat fast food.

In his twenties, after becoming a father to three and simultaneously building a business, he experienced, according to him, significant mental stress, weight gain, and chronic depression.

During that time, he estimates now, a autoimmune process began in his body that first affected the thyroid gland and then, as mentioned, the stomach lining.

Professor Bella Ongar explains, "Our stomach works like a factory.

What happens in this case is that the body develops antibodies against the cells whose job is to secrete acid.

As a result, the acidity in the stomach decreases.

Acidity is necessary for food digestion and proper absorption."

At the age of twenty-one, he was diagnosed with hypothyroidism, a condition where the gland does not produce enough hormones.

Since then, he has taken replacement thyroid hormones.

However, he writes retrospectively that it turned out the picture was more complex.

For eleven years, he suffered from low protein levels, meaning low iron stores, but without anemia.

Since his hemoglobin and hematocrit levels remained normal, the problem did not, according to him, warrant further investigation.

He tried to raise iron levels through diet and supplements, but according to him, "nothing worked".

Initially, the iron deficiency was attributed to seemingly reasonable factors: a plant-based diet, where iron comes mainly from a source that is not easily absorbed like animal iron, intensive exercise, sauna use, and pressure treatments, which he believed could increase the body's demand for iron.

However, even after trying various iron formulas and different ways of taking supplements, his protein levels remained low.

Earlier that year, after replacing his medical team as part of building a particularly expensive health protocol, his doctors decided to investigate the root cause.

According to him, they first checked the possibility of hidden blood loss from the digestive system.

He underwent a colonoscopy, which was found to be normal, thereby ruling out the possibility that the deficiency was due to prolonged bleeding from the bowel, such as from a polyp or tumor.

Simultaneously, an endoscope procedure was also performed as part of a two-way examination of the digestive system.

The turning point, according to him, came from blood tests and biopsies from the stomach.

The results obtained showed a high level of antibodies against parietal cells, the cells in the stomach involved in the production of stomach acid.

Subsequently, the biopsy results showed early signs of autoimmune gastritis, with an initial damage to the area of the stomach responsible for acid production.

"We now had a formal diagnosis," he wrote.

This new diagnosis linked three issues that appeared separate until then: iron deficiency, autoimmune disease in the stomach, and autoimmune hypothyroidism.

He claimed that each of them could exacerbate the others: low iron could affect thyroid hormone function, and thyroid underactivity could affect how the body uses iron.

Johnson added that according to conventional medical treatment, there is currently no approved cure for the disease, and the usual approach focuses mainly on monitoring, correcting deficiencies, and managing the disease.

According to him, he has already received an iron injection in the dose of one thousand milligrams, which corrected the iron deficiency.

Subsequently, he plans to continue close monitoring of indicators such as iron, protein, vitamin B twelve, gastrin, and other signs, and also to perform follow-up biopsies if necessary.

Looking ahead, he does not intend to accept this diagnosis quietly.

In the post, he wrote that he and his team will try to "solve" the disease, including through advanced characterization of immune activity and examination of experimental treatment directions.

However, he emphasized that some of the ideas he describes are still in the experimental stages or require future development.

At the end of the post, Johnson tried to turn the personal exposure into a broader message.

According to him, the fact that he did not have clear symptoms did not necessarily mean everything was fine.

His case, he wrote, is a reminder that health problems can develop silently over years, even in those who monitor their bodies obsessively to an unprecedented degree.

"The absence of symptoms is not a presence of health," he wrote, and added a call for readers to care for themselves, others, and their lives.

Blood tests found a deficiency in iron and vitamin B twelve.

Brian Johnson.

Behind Johnson's dramatic statement, "My stomach eats itself," lies the disease that is known but not always diagnosed: autoimmune gastritis.

"Gastric," meaning "of the stomach," and gastritis means inflammation of the stomach," explains Professor Bella Ongar, head of the gastroenterology-immunology department at the Gastroenterology Institute at Sheba Medical Center.

"The 'autoimmune' suggests to us the source of the inflammation.

It means this is inflammation due to the activity of the immune system.

In simple terms, the body is attacking itself.

In an average case, three percent are diagnosed."

Professor Adi Leht, head of the Gastroenterology Institute at Assuta Ashdod Medical Center, added that in autoimmune diseases, the immune system, which is supposed to protect the body from harmful factors like bacteria and viruses, "gets confused" and attacks the body's own healthy tissues.

"In the case of autoimmune gastritis, the damage is to the lining of the stomach."

"The most common link is with diseases of the thyroid gland, mainly thyroid underactivity.

There is sometimes also a link to type one diabetes, vitiligo, and other autoimmune diseases," Professor Leht stated.

"There is a complex link between stress and autoimmune diseases," she clarified.

"Chronic stress can affect the immune system, inflammation levels in the body, and hormonal balance." She added that for some people, periods of significant mental stress may be linked to the worsening of symptoms or the flare-up of an existing autoimmune disease.

"There is a complex link between autoimmune diseases, including thyroid underactivity, and other autoimmune diseases."

"The main challenge with autoimmune gastritis is that it is not always thought of at the time.

Iron or vitamin B twelve deficiency is a relatively common finding, and sometimes the initial treatment consists only of supplements.

However, when these deficiencies recur, are unexplained, or do not improve as expected, there may be room for deeper investigation."

"I am sure there are many among us who have this and are undiagnosed," says Professor Ongar.

"Many people see that they have some iron or B twelve deficiency and take supplements without necessarily performing further investigation."

Therefore, the first step in diagnosis is raising the suspicion.

Only after this possibility is placed on the table can one proceed to a systematic investigation: blood tests for characteristic antibodies, assessment of iron stores and vitamin B twelve levels, and in appropriate cases, endoscopy with biopsies of the stomach lining."

"Treatment focuses on correcting deficiencies of B twelve and iron and improving nutrition, but the disease cannot be cured.

There is also treatment with drugs that suppress the immune system, but we usually do not reach that stage."

Meanwhile, there is a need to check if there are other factors that can explain the changes in the stomach or nutritional deficiencies.

One of the main ones is the bacterium "Lactobacillus pili", which can also cause chronic inflammation and changes in the stomach lining.

"The presence of Lactobacillus can cause similar symptoms," explains Professor Ongar.

"But then we check and treat accordingly, and it can be reversible."

After diagnosis, treatment focuses mainly on correcting deficiencies and monitoring.

"It is a bit frustrating," says Professor Ongar, "the treatment focuses on correcting deficiencies of B twelve and iron and improving nutrition, but the disease cannot be cured.

We can also treat drugs that suppress the immune system, but we usually do not reach that stage."

Endoscopy.

A diagnostic tool for the disease.

Professor Leht emphasized that after diagnosis, it is important to consider further investigation for other autoimmune diseases and tailor a personalized follow-up plan for each patient.

At the same time, it is important to understand that this is a chronic condition that requires long-term monitoring, not just a one-time correction of blood tests.

The monitoring aims to reduce the risk of future complications.

Professor Leht also added that in some patients, prolonged inflammation and changes in the stomach lining can increase the risk of developing precancerous findings, stomach cancer, or small neuroendocrine tumors.

However, she emphasized that most patients with autoimmune gastritis will not develop cancer.

The main implication is not to be afraid, but to conduct systematic monitoring, usually through endoscopy and biopsies, according to the doctor's decision.

"The message is that iron or vitamin B twelve deficiency does not necessarily indicate autoimmune gastritis, but when it comes to deficiencies that cannot be explained by a clear reason, it is worth investigating and raising the issue," summarizes Professor Ongar.

"Long-term monitoring preserves health.

I also do not want to rush with cancer, but it is important to prevent complications and also correct deficiencies that can be critical from a neurological perspective."