The digestive tract contains trillions of microorganisms that interact continuously with the immune system. Researchers increasingly believe that the gut microbiome and intestinal barrier may play important roles in the development and regulation of immune responses.
Differences in the gut microbiome and increased intestinal permeability—often called “leaky gut”—have been observed in several autoimmune and inflammatory conditions. Researchers are investigating how the microbiome, intestinal barrier, diet, and other environmental factors may interact with the immune system and contribute to autoimmune disease.
This is one of the most promising areas of autoimmune research. The connection between the gut and immune system is well established, while the best ways to translate that knowledge into prevention or treatment for particular autoimmune diseases are still being determined.
A large part of the immune system is associated with the gastrointestinal tract. This makes sense: the intestinal lining must allow nutrients to enter the body while simultaneously responding to potentially harmful microorganisms and substances.
The gut microbiome helps regulate this process. Microbes produce substances that can influence immune cells, inflammation, metabolism, and the integrity of the intestinal barrier. A healthy intestinal barrier helps control what passes from the gut into the bloodstream.
When the microbiome becomes disrupted—a condition often called dysbiosis—or the intestinal barrier becomes unusually permeable, substances that would normally remain within the gut may interact differently with the immune system. Researchers are investigating whether this can help initiate or perpetuate autoimmune responses in susceptible individuals.
“Leaky gut” is the popular term for increased intestinal permeability. The intestinal lining normally forms a selective barrier, allowing nutrients to pass through while limiting the movement of microbes and other substances into the body.
Increased intestinal permeability has been documented in several autoimmune and inflammatory diseases, including celiac disease, inflammatory bowel disease, type 1 diabetes, and multiple sclerosis. Researchers are studying whether disruption of the intestinal barrier may contribute to abnormal immune activation in genetically susceptible people.
Some functional-medicine physicians, including Susan Blum, Mark Hyman, and Datis Kharrazian, place intestinal permeability near the center of their approach to autoimmune disease. They argue that identifying and addressing factors that damage the gut barrier—such as particular foods, infections, medications, stress, or microbiome disturbances—can sometimes improve autoimmune symptoms.
The scientific debate is increasingly less about whether intestinal permeability exists and more about when it contributes to disease, whether it is a cause or consequence, and how effectively restoring the intestinal barrier can change the course of autoimmune disease.
The gut microbiome is not fixed. Diet, medications, antibiotics, infections, exercise, sleep, and stress can alter its composition and activity.
Diet is one of the strongest influences. Researchers are particularly interested in fiber, fermented foods, polyphenols, and the effects of highly processed foods.
Probiotics are live microorganisms intended to provide a health benefit. Prebiotics are fibers and other compounds that feed beneficial gut microbes, helping them produce substances that may support intestinal and immune health. Prebiotic foods include onions, garlic, leeks, asparagus, artichokes, and other vegetables.
Researchers hope eventually to use diet, specific microbes, probiotics, prebiotics, or microbial products to deliberately influence immune function. This idea of precision microbiome treatment is promising, but its use in treating autoimmune disease is still developing.
Gut health is a central part of the functional-medicine approach to autoimmune disease. Physicians such as Susan Blum, Mark Hyman, and Datis Kharrazian often look for possible contributors including food sensitivities, intestinal permeability, infections, microbiome imbalance, and nutrient deficiencies.
Their approaches may include changing the diet, removing suspected food triggers, correcting nutrient deficiencies, and using probiotics, prebiotics, or other interventions intended to improve the intestinal environment.
Much of this overlaps with mainstream research into the microbiome, intestinal barrier, and immune system, and some physicians and patients report substantial improvements.
The important question is which interventions actually change autoimmune disease activity, which primarily improve symptoms or general health, and which patients are most likely to benefit. Better clinical trials should help answer these questions.
The gut microbiome and intestinal barrier interact closely with the immune system and are important areas of autoimmune research.
Increased intestinal permeability (“leaky gut”) is a measurable biological phenomenon and has been observed in several autoimmune and inflammatory diseases.
Diet is one of the strongest influences on the gut microbiome, and probiotics and prebiotics may also affect the intestinal environment.
Functional-medicine physicians place particular emphasis on restoring gut health and report substantial improvement in some patients.
The major unanswered question is whether changing the microbiome or improving the intestinal barrier can reliably alter autoimmune disease activity or help produce remission.
A peer-reviewed paper examining intestinal permeability, the gut barrier, and their possible role in autoimmune disease.
A 2025 review of advances in microbiome research in autoimmune disease, including its potential for new treatments and the challenges that remain.