Scientists have uncovered a new piece of the multiple sclerosis (MS) puzzle, and it’s hiding in the gut. In a major development, researchers have identified specific bacteria in the digestive system that may contribute to the onset of MS. While that might sound worrying at first glance, the implications are actually hopeful. By pinpointing particular gut microbes involved in the disease, scientists can now explore entirely new treatment strategies aimed at preventing or slowing MS before it causes lasting damage.
MS is a long-term autoimmune condition where the immune system mistakenly attacks the protective covering of nerve cells in the brain and spinal cord. This can lead to a wide range of symptoms, including fatigue, difficulty walking, numbness, and problems with coordination. While there are treatments that can manage symptoms or delay progression, there is still no known cure—and no clear explanation of what triggers MS in the first place. This latest research brings us one step closer to understanding that mystery.
Why the gut matters in a brain disease
It may seem odd that a condition affecting the brain and spinal cord could begin in the gut, but this idea is gaining scientific traction. The gut microbiome—a vast ecosystem of bacteria, viruses, and fungi living in our digestive system—has a powerful effect on the immune system. A growing body of research suggests that when the balance of microbes in the gut is disrupted, it can spark inflammation and immune system misfires in other parts of the body, including the brain.
In a study published in PNAS, scientists examined the gut microbiomes of 24 pairs of identical twins, where one twin had MS and the other did not. Because the twins share the same genetics and similar environments, any differences in their gut bacteria were more likely to be linked directly to the disease.
The researchers found clear microbial differences between the MS-affected twins and their healthy siblings. In particular, two bacterial species—Lachnoclostridium and Eisenbergiella tayi—were far more abundant in the MS twins. These bacteria were then transferred into germ-free mice, which subsequently developed MS-like inflammation and neurological symptoms. That result strongly suggests a causal role.
A clearer picture of how the disease develops
Another study from Yale School of Medicine offered further insight. Their team discovered that people recently diagnosed with MS had a reduced number of gut bacteria coated in immunoglobulin A (IgA)—an antibody that helps regulate the relationship between the immune system and gut microbes. This implies that the immune system in MS patients may be struggling to properly manage microbial activity in the gut, allowing harmful bacteria to thrive unchecked.
Dr. Sergio Baranzini, co-author of the twin study and a professor of neurology at the University of California, San Francisco, said: “It’s not just that these bacteria are present—it’s that they may be directly influencing the immune response that leads to MS. That opens the door to highly specific interventions.”
What’s most exciting about this discovery is that it points to a modifiable risk factor. Unlike genetics, which we can’t change, the gut microbiome is dynamic. It’s shaped by what we eat, the medications we take, and even our stress levels. If scientists can find ways to alter the gut microbiome—by removing harmful strains or encouraging the growth of protective ones—they could potentially stop MS from developing or at least ease its symptoms.
What this means for future treatment
This research could pave the way for several new types of treatment. One option is using targeted probiotics—live bacteria that can help rebalance the gut microbiome. Instead of general over-the-counter probiotics, future treatments might include tailor-made formulas designed to reduce the levels of bacteria like Lachnoclostridium or promote beneficial strains.
Another possibility is dietary intervention. Diet is one of the most powerful tools for shaping the microbiome, and certain eating patterns (like high-fibre or plant-based diets) are known to support a more diverse and stable community of gut microbes. Clinical trials could explore whether specific diets can shift the microbiome in a way that protects against MS or slows its progression.
More intensive approaches, such as fecal microbiota transplantation (FMT), are also being considered. In this procedure, gut bacteria from a healthy donor are transferred into the patient’s digestive system. FMT is already used in certain hard-to-treat infections like C. difficile, and researchers are exploring its use for autoimmune diseases as well.
Lastly, understanding the microbiome could help with earlier diagnosis. If certain bacteria are reliably present in people at high risk of MS, they could serve as biomarkers—early warning signs that prompt preventive treatment before symptoms begin.
A reason to feel hopeful
This discovery does not offer a cure—not yet. But it does offer clarity. For people living with MS, or those newly diagnosed, the idea that there’s a tangible biological process in the gut contributing to the disease can be empowering. It shifts the narrative away from helplessness and toward action.
We now know that the gut and the brain are in constant conversation, and that conversation can be influenced. As research continues, it’s likely we’ll see more personalised approaches to MS treatment—strategies that look at each patient’s unique microbiome and tailor care accordingly.
Crucially, this finding also encourages a more holistic view of neurological health. It’s no longer just about what’s happening in the brain. It’s about the whole system—the food we eat, the bacteria we carry, the immune responses we spark. And that wider perspective may be exactly what’s needed to crack conditions like MS.
As MS-UK noted in their coverage of the study, this is a “step forward in understanding the mechanisms that could underlie disease onset and progression.” More studies are already underway to explore how these bacterial strains interact with the immune system and whether they could become targets for new drugs or therapeutic protocols.
If the past decade has shown anything, it’s that the microbiome matters. And now, for MS research, it’s giving scientists and patients something they haven’t had enough of in a long time—real, evidence-based reasons to be hopeful.