Does ME/CFS involve ‘leaky gut’? This evidence-based guide explains current research on intestinal permeability, gut dysbiosis, immune activation, and what this may mean for patients with ME/CFS and complex fatigue.

People with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) are often told they have ‘leaky gut’. The more precise clinical term is increased intestinal permeability or intestinal barrier dysfunction. This refers to a situation in which the gut lining may become less effective at regulating what passes from the intestine into the rest of the body.

Current research does not support every claim commonly made online about 'leaky gut,' but it does suggest that gut dysfunction may be relevant in at least some people with ME/CFS. Recent reviews and clinical studies describe changes in the gut microbiome, reduced beneficial microbial metabolites, and possible impairment of intestinal barrier integrity as part of a wider gut–immune–brain axis involved in ME/CFS. Importantly, this is still an emerging area of research.

What current research suggests

Since 2020, review papers have increasingly described ME/CFS as a multisystem illness in which the gut microbiome may play a role alongside immune, autonomic, neurological, and metabolic abnormalities. Several recent reviews report that people with ME/CFS often show altered gut microbial composition, including reduced diversity in some studies and lower levels of metabolites such as butyrate, which is important for maintaining the intestinal barrier. These findings support the hypothesis that dysbiosis may contribute to impaired gut barrier function and immune activation in a subset of ME/CFS patients.

Emerging work has also explored whether microbial products may cross a less resilient intestinal barrier, potentially contributing to systemic inflammation or abnormal immune signalling. Researchers are investigating whether barrier dysfunction and microbial translocation may be one part of a complex disease process in ME/CFS.

One recent immunology study specifically examined the relationship between immune features and intestinal barrier function in ME/CFS, while feasibility work in severe ME/CFS has investigated antibody reactivity to intestinal microbes as a possible sign of altered immune tolerance linked to gut barrier problems. These studies are interesting and mark a foundation in the research in this area.

In summary recent research suggests the following distinctive changes in the gastrointestinal systems of ME/CFS patients:

• Lower microbial diversity
• Higher levels of Bacteroidetes and lower levels of Firmicutes
• Lower levels of anti-inflammatory bacterial species such as Bifidobacterium and Roseburia
• Lower levels of Short Chain Fatty Acid – such as Butyrate

What the evidence does not show

Current research does not prove that:

• All people with ME/CFS have “leaky gut”
• Intestinal permeability is the single root cause of ME/CFS

The strongest current message that the research offers us, is that gut dysbiosis and impaired intestinal barrier function are biologically plausible contributors in some complex fatigue patients. But as always, we need to consider gastrointestinal health as part of a multifactorial health picture.

Why the gut may matter in ME/CFS

The gut does more than digest food. It is closely linked with the immune system, nervous system, and metabolism.

Changes in the microbiome can influence:

• Production of short-chain fatty acids such as butyrate
• Regulation of inflammation
• Signalling along the gut–brain axis
• Intestinal barrier integrity
• Nutrient handling and metabolic function

In ME/CFS, this matters because 58% of patients report overlapping gastrointestinal symptoms such as:

• Bloating
• Altered bowel habits
• Food sensitivity
• Abdominal discomfort
• Brain fog
• Fatigue worsening after physical or physiological stress

That overlap does not prove cause and effect, but it helps explain why the gut has become an important focus of research, and indicates why gut health deserves careful consideration in complex fatigue.

Diet and lifestyle advice to support gut health:

Helpful foundational advice to support gut health would include:

• Eating a varied diet where tolerated
• Ensuring adequate fibre intake if appropriate for the individual
• Including foods that support a healthy microbiome, such as fibre-rich plant foods
• Avoiding unnecessarily restrictive food rules unless there is a clear clinical reason
• Correcting nutritional deficiencies
• Diving deeper with the support of comprehensive gut testing, where problems may be persistent
• A tailored gastrointestinal support protocol implemented with guidance from your Registered Nutritional Therapist at OHC

Stress and the gut

Stress, trauma and anxiety do influence gut function including: motility, sensitivity, and brain–gut signalling. It is important to remember that ME/CFS is also increasingly recognised as a neuro-immune condition, where chronic inflammation plays a key role.

Some research suggests an association between the shift in the ratio of Bacteroidetes and Firmicutes, as recognized in some ME/CFS patients, and both neurological and cognitive impairment. For example, the depletion of Firmicutes in this particular study associated with worse cognitive test scores (Prylińska-Jaśkowiaket al 2025), which is interesting when we consider the brain fog and cognitive dysfunction that is so commonly experienced in complex fatigue.

The bottom line

Research since 2020 supports the premise that some people with ME/CFS appear to have gut microbiome changes and possible intestinal barrier dysfunction, that may in turn contribute to immune activation and symptom burden.

For patients with ME/CFS or complex fatigue, and significant gastrointestinal symptoms, the best approach is a measured and informed one: comprehensive functional assessment, professional guidance and evidence-based support for gut health. This is certainly an area of expertise at OHC.

References

Tokarz-Deptuła B, Deptuła W, Stosik M, et al. Gut Microbiome and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Insights into Disease Mechanisms. Microorganisms. 2024.

Lim EJ, Son CG. Clinical evidence of the link between gut microbiome and myalgic encephalomyelitis/chronic fatigue syndrome: a retrospective review. J Transl Med. 2024.

Cabanas H, Muraki K, Eaton-Fitch N, et al. The gastrointestinal microbiota in the development of ME/CFS: a critical view and potential perspectives. Front Immunol. 2024.

Thapaliya K, Marshall-Gradisnik S, Eaton-Fitch N. The potential therapeutic approaches targeting gut health in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): a narrative review. Front Microbiol. 2025.

van Elzakker MB, Brumfield SA, Lara Mejia PS. Investigating Antibody Reactivity to the Intestinal Microbiome in Severe Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): A Feasibility Study. Brain Behav Immun Health. 2023.

Steiner S, Becker SC, Hartwig J, et al. Immunological Patient Stratification in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. J Transl Med. 2024.

Theoharides TC, Stewart JM, Hatziagelaki E, et al. The Gut-Brain-Immune Axis in Environmental Sensitivity Illnesses: Microbiome-Centered Narrative Review of Fibromyalgia Syndrome, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, and Multiple Chemical Sensitivity. Biomedicines. 2025.