Bryan Johnson, the American tech entrepreneur and millionaire who in recent years has become one of the most 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 that affects the stomach.
“My stomach is eating itself,” wrote Johnson, 48, who is best known for his extreme attempts to slow aging and monitor nearly every possible metric in his body, in a detailed post published on X.
The disease Johnson was diagnosed with is called autoimmune gastritis, or AIG. It is a condition in which the immune system mistakenly attacks cells in the stomach lining. According to Johnson, it is a difficult-to-detect disease that often remains silent for years and over time can cause nutritional deficiencies, anemia and an increased risk of additional complications. He said the disease affects about 2% to 5% of the population, and perhaps even more, because in many cases it goes undiagnosed.
The disclosure drew particular interest precisely because of Johnson’s identity. In recent years, he has built an extreme health project around himself, maintaining an especially strict routine that includes measured nutrition, workouts, frequent blood tests, sleep monitoring, fertility tracking, supplements, medical treatments and various experiments intended, he says, to slow the pace of aging. It has been reported in the past that he spends millions of dollars a year trying to preserve his body in optimal condition. Now, the man who presents himself as someone seeking to push the boundaries of preventive medicine says a significant disease developed in his body for years with almost no one noticing.
In his post, Johnson described how his health journey did not always look the way it does today. As a child, he said, he ate sugar-heavy cereals, drank sweetened beverages and ate fast food. In his 20s, after becoming a father of three while building a business, he experienced significant mental strain, weight gain and chronic depression. During that period, he now believes, an autoimmune process began in his body, first affecting his thyroid gland and later, as noted, the lining of his stomach.
At 21, he was diagnosed with hypothyroidism, a condition in which the thyroid gland does not produce enough hormones. Since then, he said, he has been treated with replacement thyroid hormones. But in hindsight, he wrote, the picture proved more complex. For 11 years, he suffered from low ferritin levels, meaning low iron stores, but without anemia. Because his hemoglobin and hematocrit levels remained normal, he said, the problem did not receive a sufficient workup. He tried to raise his iron levels through diet and supplements, but, he said, “nothing worked.”
Three problems, one diagnosis
At first, the iron deficiency was attributed to factors that seemed reasonable: a plant-based diet, in which iron comes mainly from a source that is not absorbed as easily as iron from animal products; intensive training; sauna use; and hyperbaric chamber treatments, which he said may increase the body’s need for iron. But even after trying different iron formulas and different ways of taking the supplements, his ferritin levels remained low.
Earlier this year, after replacing his medical team as part of building a new and especially expensive health protocol, his doctors decided to return to the workup from the beginning. He said they first checked for the possibility of hidden blood loss from the digestive system. He underwent a colonoscopy, which was normal, ruling out the possibility that the deficiency stemmed from prolonged intestinal bleeding, such as from a polyp or tumor. At the same time, a gastroscopy was also performed as part of a two-way examination of the digestive system.
The turning point, he said, came in blood tests and stomach biopsies. Around the time of the test, results showed a high level of antibodies against parietal cells, cells in the stomach involved in producing stomach acid. Later, the biopsy results arrived and showed early signs of autoimmune gastritis, with initial damage to the area of the stomach responsible for acid production. “Now we had an official diagnosis,” he wrote.
The new diagnosis connected three problems that until then had seemed separate: the iron deficiency, the autoimmune disease in the stomach and autoimmune hypothyroidism. He argued that each can make the other more difficult: Low iron may affect thyroid hormone function, and hypothyroidism may affect how the body uses iron.
Johnson added that according to standard medical treatment, there is currently no approved cure for the disease, and the accepted approach focuses mainly on monitoring, correcting deficiencies and managing the condition. He said he has already received a 1,000-milligram iron infusion, which helped correct the iron deficiency. Going forward, he plans to continue regular monitoring of measures such as iron, ferritin, vitamin B12, gastrin and other markers, and to undergo repeat biopsies as needed.
As expected, 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 described are only in experimental stages or even require future development.
At the end of the post, Johnson tried to turn his personal disclosure into a broader message. He said the fact that he had no clear symptoms did not necessarily mean everything was normal. His case, he wrote, is a reminder that health problems can develop quietly for years, even in someone who tracks his body with almost unprecedented obsession. “The absence of symptoms is not the presence of health,” he wrote, adding a call for readers to care for themselves, others and life itself.
Blood tests found iron and vitamin B12 deficiencies; Bryan Johnson
(Photo: Instagram)
The silent disease that begins in the stomach
Behind Johnson’s dramatic statement, “my stomach is eating itself,” is a known but not always diagnosed disease: autoimmune gastritis.
Prof. Bela Ungar “Gastric means ‘of the stomach,’ and gastritis is inflammation of the stomach,” explains Prof. Bela Ungar, director of the gastro-immunology service at Sheba Medical Center’s gastroenterology institute at Tel Hashomer. “The ‘autoimmune’ tells us the source of the inflammation. It means this is inflammation caused by activity of the immune system. In simple terms, the body attacks itself. On average, 3% are diagnosed with it.”
Prof. Adi Lahat, director of the gastroenterology institute at Assuta Ashdod Public Hospital, adds that in an autoimmune disease, the immune system, which is supposed to protect the body from harmful agents such as bacteria and viruses, becomes “confused” and attacks the body’s own healthy tissues. “In the case of autoimmune gastritis, the damage is to the stomach lining.”
Prof. Adi Lahat Photo: PrivateThe stomach lining is not merely an internal coating. It is responsible for part of the process of breaking down food, secreting essential substances and helping absorb nutrients.
“Our stomach works like a factory: There are cells responsible for absorption, cells responsible for secreting mucus, cells that secrete certain hormones and cells that secrete acid,” Ungar explains. “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 level in the stomach drops.”
That decrease is important because the stomach is one of the most acidic areas of the digestive system, and acidity is necessary for breaking down food and properly absorbing certain components, including iron. In addition, as part of the autoimmune inflammation, antibodies are also created against intrinsic factor, a factor essential for proper absorption of vitamin B12.
Over time, this process can cause deficiencies in vitamin B12 and iron. When these deficiencies persist, they can lead to anemia and general symptoms that are not unique to one disease.
“A person suffering from anemia feels weakness and fatigue. Sometimes there is also abdominal pain as a result of all the inflammation in the stomach,” Ungar says. “Sometimes there are even neurological symptoms, because B12 itself is essential for many neurological processes: tingling, muscle weakness, imbalance, lack of concentration.”
That is one reason the disease may be discovered through blood tests rather than through clear digestive complaints. Lahat adds that “when symptoms do appear, they can include pain or discomfort in the upper abdomen, a feeling of bloating, nausea, fatigue, weakness or dizziness.”
Damage to the stomach lining; autoimmune gastritis
(Photo: Shutterstock)
A clue to other diseases
Because it is an autoimmune process, autoimmune gastritis can appear alongside other autoimmune diseases. That is also the context that emerged in Johnson’s case, after he said he had previously been diagnosed with hypothyroidism.
“The most common connection is with thyroid diseases, mainly hypothyroidism. Sometimes there is also a connection to type 1 diabetes, vitiligo and other autoimmune diseases,” Lahat notes. Ungar says celiac disease can also be found on the list of possible associations, “though this connection is weaker.”
Another question often raised around autoimmune diseases concerns the role of stress. Lahat clarifies that emotional stress is generally not considered a single cause that explains the onset of the disease, but it may affect the immune system and the body’s overall balance.
“There is a complex connection between stress and autoimmune diseases,” she says. “Prolonged stress can affect the immune system, inflammation levels in the body and hormonal balance.” In some people, she adds, periods of significant emotional strain may be linked to worsening symptoms or a flare-up of an existing autoimmune disease.
A complex link to other autoimmune diseases, including autoimmune hypothyroidism
(Photo: Shutterstock)
How is it diagnosed, and how is it treated?
The main challenge in autoimmune gastritis is that doctors do not always think of it in time. Iron or vitamin B12 deficiency is a relatively common finding, and sometimes initial treatment consists of supplements alone. But when the deficiencies return, are unexplained or do not improve as expected, a deeper workup may be warranted.
“I am sure there are many people walking around among us who have it and have not been diagnosed,” Ungar says. “Many people will see that they have a slight iron deficiency or low B12 and will take supplements without necessarily undergoing further evaluation.”
Therefore, the first step in diagnosis is raising the suspicion. Only after that possibility is on the table can a proper workup proceed: blood tests for characteristic antibodies, assessment of iron stores and vitamin B12 levels, and, in appropriate cases, gastroscopy with biopsies from the stomach lining.
At the same time, doctors must check whether other factors could explain the changes in the stomach or the nutritional deficiencies. One of the main ones is Helicobacter pylori, a bacterium that can also cause chronic inflammation and changes in the stomach lining.
“The presence of Helicobacter can cause similar phenomena,” Ungar explains. “But then it is tested for and treated accordingly, and it can be reversible.”
After diagnosis, treatment focuses mainly on correcting deficiencies and monitoring. “It is a bit frustrating,” Ungar says. “Treatment focuses on supplementing B12 and iron deficiencies and improving nutrition, but the disease cannot be cured. It is also possible to treat it with medications that suppress the immune system, but usually we do not reach that point.”
A gastroscopy; one of the diagnostic tools for the disease
(Photo: Shutterstock)
Lahat emphasizes that after diagnosis, it is important to consider screening for additional autoimmune diseases and to tailor a personal monitoring 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 test results.
Monitoring is also intended to reduce the risk of future complications. Lahat adds that in some patients, prolonged inflammation and changes in the stomach lining may increase the risk of developing precancerous findings, stomach cancer or small neuroendocrine tumors. However, she stresses that most patients with autoimmune gastritis will not develop malignancy. The main significance is not to panic but to undergo orderly monitoring, usually with gastroscopy and biopsies according to the doctor’s decision.
The message is that iron or B12 deficiency does not necessarily indicate autoimmune gastritis, but when the deficiencies are not explained by a clear cause, it is worth not settling for supplements alone.
“If there are any nutritional deficiencies that are not explained by other causes, it is worth doing the workup and raising the issue,” Ungar concludes. “Long-term monitoring protects health. I also do not want to alarm people about malignancy, but it is important to prevent complications and also to correct deficiencies that can be critical neurologically.”