Multiple Sclerosis (MS) is a chronic neurological condition in which the immune system mistakenly attacks the protective coating around nerves, known as myelin. For years, MS was considered purely a disease of the central nervous system — but new research shows that it may actually begin much further south, in the gut.
Our intestines are home to trillions of bacteria that play vital roles in digestion, metabolism, and immune regulation. This microbial community, called the gut microbiome, is now understood to influence inflammation and even the way our immune system behaves. In MS, an imbalance in gut bacteria — known as dysbiosis — may be a key factor driving immune dysfunction and disease progression.
How the Gut Talks to the Brain
The gut and brain are deeply connected through what scientists call the gut–brain–immune axis. Gut microbes produce chemicals and metabolites that send signals through the bloodstream and the vagus nerve, directly influencing brain inflammation, energy balance, and immune activity.
When the microbiome is balanced and diverse, it promotes immune tolerance and reduces inflammation. But when this ecosystem becomes disrupted — from antibiotics, stress, poor diet, or infections — the result can be an overactive immune system and a breakdown in immune regulation, both central features of MS.
What the Research Shows
Over the past decade, numerous studies have compared the gut bacteria of people with MS to those of healthy individuals. These studies consistently reveal differences in the types and amounts of bacteria present.
Researchers have found that:
- People with MS often have more inflammatory bacteria and fewer protective species.
- Newly diagnosed patients show reduced immune regulation in the gut, including fewer bacteria coated with protective IgA antibodies.
- When MS patients start certain immune therapies, their microbiome tends to shift toward a healthier, more balanced state — suggesting a two-way relationship between gut bacteria and immune activity.
These findings point toward the microbiome as a powerful influencer in the development and progression of MS.
The Key Bacteria Linked to MS
Several bacterial species have been identified as potential contributors to MS — some harmful, others protective.
- Eisenbergiella tayi and Lachnoclostridium species have been shown in research on identical twins (where one has MS and the other does not) to promote MS-like disease in experimental models.
- Blautia often appears in higher numbers in people with MS and may promote gut and systemic inflammation.
- Tyzzerella nexilis, another emerging bacterium of interest, has been found in greater abundance in MS patients. This microbe is associated with inflammation and metabolic dysfunction, and its overgrowth may signal a microbiome under stress — one that fuels immune overactivation rather than balance.
- Akkermansia muciniphila, typically considered beneficial, can become problematic when overgrown, as it breaks down the gut’s protective mucous layer, potentially increasing gut permeability or “leaky gut.”
- In contrast, Prevotella, Bifidobacterium, and Faecalibacterium prausnitzii are typically depleted in MS. These species produce short-chain fatty acids (like butyrate and propionate) that calm inflammation, nourish gut cells, and promote healthy immune regulation.
Together, these microbial shifts reflect a loss of protective species and an increase in those linked with inflammation — a pattern that mirrors the immune imbalance seen in MS.
How Gut Dysbiosis Can Influence MS
Scientists are uncovering several mechanisms that may explain how the microbiome affects MS risk and progression:
- Immune Modulation:
Beneficial bacteria help train the immune system to stay calm. When they decline, inflammatory immune cells become more active, promoting autoimmune responses. - Leaky Gut:
Some bacteria, like Akkermansia and Tyzzerella, can weaken the gut barrier. This allows bacterial fragments and toxins to pass into the bloodstream, triggering inflammation that may spread to the brain. - Molecular Mimicry:
Certain bacterial proteins resemble those found in myelin. This similarity may “confuse” the immune system, leading it to attack the body’s own nerve tissue. - Loss of Protective Metabolites:
Without enough beneficial bacteria, levels of anti-inflammatory compounds like butyrate fall — weakening the body’s natural ability to regulate immune activity.
Supporting the Gut–Brain Connection
While the research is ongoing, there’s growing agreement that nurturing the gut microbiome is a vital part of supporting people with MS. Diets rich in fibre, colourful vegetables, and plant diversity help nourish beneficial microbes that produce anti-inflammatory compounds. Reducing processed foods, sugar, and alcohol can also help restore microbial balance.
Some emerging therapies — such as targeted probiotics, prebiotics, and dietary interventions — are being explored as complementary treatments. Interestingly, some MS medications also appear to normalise the microbiome, suggesting that the immune system and gut bacteria may heal in tandem.
The Bottom Line
The connection between MS and the gut microbiome is one of the most exciting developments in neurological research. An imbalance in gut bacteria — including overgrowth of species like Tyzzerella nexilis, Eisenbergiella tayi, and Blautia, and loss of protective bacteria like Prevotella and Faecalibacterium — appears to influence inflammation and immune activity in profound ways.
By supporting gut health through diet, lifestyle, and targeted pre and probiotic therapies, it may be possible to calm immune activity, protect the nervous system, and improve long-term outcomes for people with MS.
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Naturopath, Nutritionist and Buteyko Practitioner at Elemental Health, St. Ives - Sydney.