Gut Health & Autoimmunity
The digestive tract contains trillions of microorganisms that interact continuously with the immune system. Researchers are increasingly studying how the gut microbiome and intestinal barrier may influence immune responses and autoimmune disease.
Differences in the microbiome and increased intestinal permeability—often called “leaky gut”—have been observed in several autoimmune and inflammatory conditions.
The connection between the gut and immune system is well established. The more difficult question is whether changing the microbiome or intestinal barrier can prevent or substantially alter autoimmune disease.
The Gut-Immune Connection
Much of the immune system is associated with the gastrointestinal tract. The intestinal lining must absorb nutrients while limiting the entry of potentially harmful microorganisms and substances.
Gut microbes produce compounds that can influence immune cells, inflammation, metabolism, and the intestinal barrier.
When the microbiome is disrupted—often called dysbiosis—or intestinal permeability increases, interactions between microbes, their products, and the immune system can change. Researchers are investigating whether these changes can contribute to autoimmune disease in susceptible people.
What Is “Leaky Gut”?
“Leaky gut” is the popular term for increased intestinal permeability, a measurable biological phenomenon.
It has been observed in conditions including celiac disease, type 1 diabetes, and multiple sclerosis, as well as inflammatory bowel disease, which is generally classified as an immune-mediated inflammatory disease.
The important questions are whether increased permeability is a cause, consequence, or both, and whether restoring the intestinal barrier can meaningfully change the course of disease.
Some functional-medicine physicians, including Susan Blum, Mark Hyman, and Datis Kharrazian, place particular emphasis on intestinal permeability and gut health in treating people with autoimmune disease.
Can the Microbiome Be Changed?
The microbiome is not fixed. Diet, medications, antibiotics, infections, exercise, sleep, and stress can influence its composition and activity.
Diet is one of its major influences. Researchers are particularly interested in fiber, fermented foods, polyphenols, and highly processed foods.
Probiotics provide live microorganisms, while prebiotics are fibers and other compounds used by beneficial gut microbes. Researchers are investigating whether diet, probiotics, prebiotics, or specific microbial products can eventually be used to influence immune function.
The possibilities are intriguing, but microbiome-based treatments for autoimmune disease are still developing.
The Functional Medicine Approach
Functional medicine often places gut health near the center of autoimmune treatment. Approaches may include changing diet, investigating possible food triggers, correcting nutrient deficiencies, and using probiotics, prebiotics, or other interventions intended to alter the intestinal environment.
Some of this overlaps with mainstream research into the microbiome, intestinal barrier, and immune system. But evidence for particular tests and treatments varies considerably.
The key question is which interventions actually change autoimmune disease activity, which primarily improve symptoms or general health, and which patients are most likely to benefit.
Key Takeaways
The gut microbiome and intestinal barrier interact closely with the immune system.
Increased intestinal permeability (“leaky gut”) is a real biological phenomenon, although its role differs among diseases.
Diet can substantially influence the microbiome, while probiotics and prebiotics may also affect the intestinal environment.
Functional medicine places particular emphasis on restoring gut health, but evidence for individual interventions varies.
Whether changing the microbiome or intestinal barrier can reliably alter autoimmune disease activity or contribute to remission remains an important research question.
Learn More
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 possible new treatments and the challenges that remain.