MCAS Research: Could Gut Bacteria Play a Role in Chronic Fatigue?

Scientists linked chronic fatigue to a deficiency in butyrate-producing bacteria.

Recent breakthroughs published in Cell Host & Microbe and Nature Medicine have uncovered a profound connection between the gut microbiome and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Most notably Faecalibacterium prausnitzii.

Recent breakthroughs published in Cell Host & Microbe and Nature Medicine have uncovered a profound connection between the gut microbiome and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Researchers from Columbia University and the Jackson Laboratory found that patients suffering from this debilitating condition often lack specific health-promoting bacteria, most notably Faecalibacterium prausnitzii. This deficiency leads to a critical shortage of butyrate, a short-chain fatty acid essential for maintaining the gut barrier and regulating energy metabolism. Without these vital microbial components, the body enters what experts describe as a "gut-driven energy crisis," directly impacting a patient's physical and mental stamina.

The implications of these findings are transformative for the millions of people living with chronic fatigue. The studies demonstrated that the reduction of beneficial microbial species like Roseburia and Coprococcus is directly correlated with the severity of a patient's symptoms. By pinpointing these specific biological markers, scientists are now closer than ever to developing precise diagnostic tools and therapeutic interventions that target the microbiome. Rather than treating fatigue as a vague symptom, medical professionals can now look toward restorative gut treatments as a viable path to reclaiming energy and health.

source: Cell Host & Microbe and Nature Medicine (2025). Microbial Alterations and the Gut-Driven Energy Crisis in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

This has actually been at the center of my most recent research. A small retrospective review of 12 patients diagnosed with MCAS (and concurrent autoimmune markers) found that all 12 had abnormal stool microbiome results and most had low short‑chain fatty acids like butyrate on testing. There’s reason to think low butyrate could be common in MCAS and related conditions because many people with MCAS have gut microbiome disruptions, reduced diversity, or reduced butyrate‑producing species — but actual controlled prevalence studies aren’t published yet. Most of the literature linking MCAS and the microbiome focuses on dysbiosis and patterns like SIBO (small intestinal bacterial overgrowth) — which itself can relate to lower butyrate‑producing bacteria.

If you would like our lab to give you a complete GI Map of your Gut Microbiome, you can order the test direct from our lab here. The GI-MAP Stool test measures good + bad gut bacteria, inflammation, digestion, and immunity to clarify underlying problems that doctors may miss, such as bloating, IBS, brain fog, and more.

🧪 GI-MAP Stool Test helps you order a clear gut snapshot: microbes + digestion + inflammation markers.

😣 Useful when bloating, irregular stools, food reactions, brain fog, skin rashes or "mystery" flare-ups keep coming back.

🧬 Add-ons like Zonulin, Gluten Peptide, Antibiotic Resistance Genes, and StoolOMX can answer focused "why" questions.

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🗺️ Next step: order, follow prep, then use results to prioritize pathogens, inflammation, and support markers, and more.

Our GI-MAP Stool Test looks for common gut imbalances, infections, digestion, and inflammation markers from one at-home stool sample. This is the perfect test to see where you are with butyrate producing bacteria, as well as other conditions such as H.Pylori. You collect at home, ship the kit back, and get a clear report of your gut environment. Ordering the GI Map Test can help turn "random gut issues" into a clearer pattern across microbes, inflammation, and digestion in one report. Because it measures microbial DNA, it may detect low-level signals that deserve measuring, especially if your symptoms match and you've had, antibiotics, or recurring autoimmune flare-ups.

Mapping your gut can be a practical choice if bloating, irregular stools, food reactions, brain fog, skin rashes or stubborn GI discomfort keep pulling you into guesswork. Many people also add targeted add-ons when they want the report to answer other specific questions Available add-ons (what they are + why they can matter):

• Zonulin: An add-on marker sometimes used to provide extra context about gut barrier stress when symptoms flare with foods or stress.

• Gluten Peptide: Helps indicate recent gluten exposure, which can be useful when you're trying to confirm strict avoidance or identify hidden gluten.

• Antibiotic resistance genes for bacteria: Adds resistance-gene testing to see what antibiotics could be the most effective in treating the specific type of bad bacteria infections you may have.

• StoolOMX bile acids test: Adds bile acids (and related stool metabolites) to help clarify bile-related diarrhea, constipation patterns, and gut-metabolism clues.

Summary of each biomarker category:

• Pathogens: Screens for organisms more likely to be tied to acute or persistent GI infections.

• Beneficial bacteria: Shows helpful microbes associated with gut balance and day-to-day digestive stability.

• Opportunistic bacteria: Highlights organisms that can become a problem when they overgrow or the gut environment shifts.

• Fungal and yeast overgrowth: Detects yeast and fungal signals that may matter when symptoms linger or recur.

• Digestive enzymes: Includes markers that reflect how well you're breaking down food, especially fats and proteins.

• Inflammation markers: Helps clarify whether irritation/inflammation may be contributing to symptoms.

• Immune function: Includes markers that reflect immune activity along the gut lining.

• Fat malabsorption: Points to signs you may not be absorbing fats efficiently.

• H. pylori: Reports H. pylori DNA with added context that can support more targeted next steps.

At the end of this article I will give you more detailed information regarding this GI Map Test. Use this order link to receive special discounted pricing. But first, more about Butyrate.

Butyrate is a short-chain fatty acid produced mainly by beneficial gut bacteria when they ferment dietary fiber. It’s crucial for gut health, immune regulation, and inflammation control. When butyrate levels are low, a few things happen that can trigger or worsen MCAS:

1. Gut barrier dysfunction (leaky gut): Butyrate is a primary fuel for colonocytes (cells lining the gut). Low butyrate weakens these cells and reduces tight junction proteins, making the gut more “leaky.” A leaky gut allows undigested proteins, bacterial fragments, and other antigens to enter circulation, which can directly stimulate mast cells systemically. Mast cells are hyper-responsive to such “danger signals.”

2. Reduced anti-inflammatory signaling: Butyrate helps regulate immune cells, particularly by promoting regulatory T cells (Tregs) and anti-inflammatory cytokines. Without enough butyrate, the immune system skews toward pro-inflammatory responses, creating an environment where mast cells are more easily activated.

3. Histone deacetylase (HDAC) inhibition: Butyrate acts as an HDAC inhibitor, which epigenetically modulates gene expression in immune cells. Low butyrate removes this “brake,” potentially increasing mast cell proliferation or hypersensitivity.

4. Microbiome imbalance: Low butyrate often reflects dysbiosis (loss of butyrate-producing bacteria). Dysbiosis itself can increase mast cell activity by producing metabolites that irritate the gut or by failing to suppress immune overactivation.

5. Neuro-immune signaling: Butyrate affects the enteric nervous system and vagal tone. Low levels may enhance stress signaling in the gut, which in turn can trigger mast cells, since mast cells are highly responsive to neuropeptides like substance P and CRH (corticotropin-releasing hormone).

So, in short, low butyrate indirectly primes mast cells by weakening the gut barrier, tilting immune balance toward inflammation, and removing epigenetic control—all of which make mast cells more reactive, which is essentially what MCAS is.  

The reason research on MCAS and the microbiome—especially on butyrate levels—is so limited comes down to a few key issues:

1. MCAS itself is hard to diagnose consistently.

   There’s no single lab test that definitively diagnoses MCAS. Diagnosis often relies on a combination of clinical symptoms (flushing, hives, GI issues, anaphylaxis), elevated mediators like tryptase or histamine, and sometimes response to mast cell–directed therapy. This variability makes it tough to gather large, homogeneous study populations.

2. Small patient populations in research.

   MCAS is considered underdiagnosed, so most studies are done on small cohorts or case series. Small sample sizes limit the ability to detect statistically robust correlations between things like butyrate levels and mast cell activation.

3. Microbiome testing is complex.

   Measuring butyrate isn’t as simple as drawing blood. Most studies rely on stool samples, which vary depending on diet, timing, and the lab’s methods. Some use gas chromatography–mass spectrometry, others use metabolomic panels, and results aren’t standardized across studies.

4. Multiple confounding factors.

   People with MCAS often have overlapping conditions—IBS, EDS, SIBO, mold illness, or autoimmune disorders—all of which independently influence gut microbiota and butyrate production. This makes it hard to tell if low butyrate is specific to MCAS or a side effect of coexisting gut issues.

5. Funding and research priorities.

   MCAS and mast cell disorders are relatively niche compared to big autoimmune or metabolic diseases. That means fewer large, well‑funded studies, especially ones combining detailed microbiome and metabolomic data.

Because of these challenges, most evidence linking low butyrate to MCAS is anecdotal or from small observational studies. Researchers often infer the connection based on patterns: MCAS patients frequently have gut dysbiosis, reduced diversity, SIBO, or low populations of butyrate-producing bacteria—but we still lack solid prevalence numbers.

This is a gut GI Map test that gives you a complete overview of your gut health. 

The simplest ways to boost butyrate are mostly dietary and gut-microbiome–friendly, because butyrate is produced by bacteria fermenting fiber in your colon.

Here’s the breakdown:

Quick ways to raise butyrate:

1. High-fiber foods (prebiotics):

   
   

   • Resistant starches (cooled potatoes, green bananas, plantains)

   • Oats, barley, beans, lentils

   • Vegetables like asparagus, leeks, onions, garlic

     These feed butyrate-producing bacteria in your gut so they can make it naturally.

   
   

2. Fermented foods:

   
   

   • Sauerkraut, kimchi, kefir, yogurt

   • These don’t provide butyrate directly but help maintain a healthy gut microbiome that supports butyrate producers.

   
   

3. Direct butyrate supplements (like sodium butyrate):

   
   

   • Can be taken in capsules, often enteric-coated to survive stomach acid.

   • Used especially if gut dysbiosis is severe or fiber can’t be tolerated.

Why it’s done with food:

• Butyrate is produced by bacterial fermentation. Taking it with fiber or food ensures it reaches the colon where bacteria live.

• Food slows digestion, so more of the compound gets to the lower gut rather than being absorbed too early.

• Combining it with prebiotic fibers multiplies the effect: you get direct supplementation + natural bacterial production.

GI MAP TEST SPECIFICS:

MICROBIOME FLORA (GOOD BACTERIA):

• Bacteroides fragilis: Plays a key role in developing a robust immune system and preventing harmful inflammation in the digestive tract.

• Bifidobacterium: Important for breaking down food, fighting harmful bacteria, and producing essential vitamins (B1, B2, B3, B6, B9 (folic acid), B12, vitamin K) that support proper function of all cells.

• Enterococcus: Contributes to a healthy gut environment and assists in the digestion process, converting food into energy.

• Escherichia (E. Coli): Certain strains can be harmful, while others are helpful, maintaining the integrity of the intestinal barrier and preventing infections.

• Lactobacillus: Needed to maintain a healthy balance of gut flora, warding off pathogens, and aiding in digestion.

• Akkermansia mucinophila: Helps reinforce the mucous layer in the gut, acting as a protective barrier and playing a role in metabolic processes. Imbalances of Akkermansia can lead to unexplained weight gain.

• Clostridia: Involved in the synthesis of important nutrients and the maintenance of a healthy and balanced gut microbiota.

• Faecalibacterium prausnitzii: Has anti-inflammatory properties that are crucial for the health of the gut lining and preventing disorders like Irritable Bowel Syndrome (IBS).

• Roseburia: Known to produce butyrate, a short-chain fatty acid that fuels colon cells and supports a healthy colon.

BAD BACTERIA:

• Campylobacter: Causes foodborne illness with symptoms like fever, diarrhea, and abdominal pain, often from undercooked poultry.

• Clostridium difficile, Toxin A: Releases toxins that damage the intestines, leading to severe diarrhea and colitis, often after antibiotic use.

• Clostridium difficile, Toxin B: Similar to Toxin A, it also causes severe intestinal conditions and is associated with hospital-acquired infections.

• E. coli: Some strains like O157:H7 can cause severe stomach cramps, bloody diarrhea, and vomiting. There are other strains that are healthy for us.

• Enterotoxigenic E. coli LT: Produces a toxin causing watery diarrhea, especially in children in developing countries.

• Enterotoxigenic E. coli ST: Produces a toxin and is a common cause of traveler's diarrhea.

• Shiga-like Toxin E. Coli stx1: Produces a toxin causing hemorrhagic colitis and can lead to a severe condition known as hemolytic uremic syndrome.

• Shiga-like Toxin E. Coli stx2: Similar to stx1, but often associated with more severe outcomes and complications.

• Shigella: Can cause symptoms like fever, stomach pain, and diarrhea, which can be bloody.

• Salmonella: Can produce symptoms like diarrhea, bloating, fever, and abdominal cramps, often from contaminated food.

• Vibrio cholera: Responsible for cholera, which causes severe watery diarrhea and can lead to dehydration and death if untreated.

• Yersinia enterocolitica: Often leads to yersiniosis, causing symptoms like diarrhea, fever, and abdominal pain, sometimes leading to severe complications.

VIRUSES:

• Adenovirus 40/41: Commonly causes diarrhea in children and can also lead to respiratory infections.

• Norovirus GI: A leading cause of gastroenteritis, with symptoms including diarrhea, vomiting, nausea, and stomach pain.

• Norovirus GII: Similar to GI but is the most common cause of norovirus outbreaks worldwide.

• Rotavirus A: Highly contagious virus causing severe diarrhea, vomiting, fever, and abdominal pain, primarily in infants and young children.

PARASITES:

• Cryptosporidium: Causes cryptosporidiosis, leading to watery diarrhea, which can be particularly severe in immunocompromised individuals like those with autoimmune diseases.

• E. histolytica: Can result in lack of energy, weight loss, and GI issues, which can lead to dysentery with bloody diarrhea, and liver abscess if it spreads.

• Giardia: Causes giardiasis, characterized by symptoms such as foul-smelling diarrhea, stomach cramps, bloating, and nausea.

HELICOBACTER PYLORI (H.PYLORI):

• H. Pylori: Known for causing ulcers in the stomach lining and increasing the risk of stomach cancer. This pathogen is also linked to chronic gastritis and peptic ulcers. Pro Knowledge: It can also slow stomach acid production, leading to fermentation and bubbling of food in the stomach, which can then lead to acid reflux.

• Virulence Factor, cagA: A protein associated with H. pylori, which increases its ability to cause damage and leads to more severe gastric diseases.

• Virulence Factor, vacA: A toxin produced by H. pylori that can lead to cell death in the stomach lining and contribute to ulcer formation.

OPPORTUNISTIC BACTERIA:

• Citrobacter freundii: Can cause infections in the urinary tract and other parts of the body, may trigger symptoms in autoimmune conditions.

• Klebsiella pneumoniae: Known to cause pneumonia, it can also lead to other infections, particularly in individuals with weakened immune systems like autoimmune disease.

• Proteus: A group of bacteria that can cause urinary tract infections and may be linked to rheumatoid arthritis.

• Proteus mirabilis: This specific strain is also associated with urinary tract infections and could be implicated in kidney stone formation.

• Methanobacteriaceae: A family of bacteria that produces methane, which can negatively affect the overall balance of the gut microbiome.

• Fusobacterium: These bacteria are associated with several infections, including periodontal disease (like gum disease), and may have links to colorectal cancer.

• Desulfovibrio: Known for producing hydrogen sulfide, which can damage the gut lining and is associated with inflammatory bowel diseases (IBD).

OVERGROWTH BACTERIA:

• Morganella: Normally found in the human intestine, but if it overgrows, it can cause infections, particularly in the urinary tract.

• Pseudomonas: Known for its resistance to antibiotics and can cause various infections if it overgrows.

• Pseudomonas aeruginosa: A specific strain of Pseudomonas that can lead to respiratory system infections and is particularly problematic in hospitals.

• Staphylococcus: Can cause skin infections, pneumonia, and food poisoning when they overpopulate.

• Streptococcus: Can cause a wide range of health issues, from strep throat to more serious conditions like rheumatic fever if it grows unchecked.

OTHER PARASITES:

• Blastocystis hominis: Commonly found in the intestine; can sometimes cause digestive symptoms, but many people have no symptoms at all.

• Dientamoeba fragilis: May cause diarrhea, bloating, and stomach pain, although it is often found in people who have no digestive symptoms.

• Endolimax nana: Usually doesn't cause problems but can be associated with gastrointestinal symptoms if they overgrow.

• Entamoeba coli: Not to be confused with E. coli bacteria, this parasite is typically harmless but can sometimes be a sign of poor sanitary conditions.

• Chilomastix mesnelli: Often found in the human digestive tract and usually doesn't cause disease or symptoms but still is important in the overall microbiome.

• Pentatrichomonas hominis: Considered non-disease causing, but its presence may indicate exposure to other pathogens or poor hygiene.

FUNGI/YEAST:

• Candida albicans: This yeast can cause infections like thrush and yeast infections, particularly in individuals with weakened immune systems like autoimmunity.

• Candida: Similar to Candida albicans, these species can lead to various candidiasis infections, affecting skin, genitals, throat, and more.

• Geotrichum: Can cause a rare condition called geotrichosis, affecting the skin, bronchi, and lungs, mostly in immunocompromised individuals, such as those with autoimmune disease.

• Microsporidium: These are microscopic parasites that can cause chronic diarrhea and wasting in people with compromised immune systems, such as those with AIDS and autoimmunity.

• Trichosporon: Typically harmless but can occasionally cause infections like white piedra, affecting the hair shafts, or more serious systemic infections if in the gut.

You can order this test direct from our lab using this link for special discounted pricing.

The GI-MAP test goes beyond standard stool testing by using DNA technology to detect hidden infections, microbiome imbalances, and immune markers in the gut. Because mast cell activation is often triggered by gut inflammation, dysbiosis, and chronic infections, this deeper analysis can help identify underlying drivers that traditional tests frequently miss.

Why our GI-MAP Test Can Be Better for Investigating MCAS:

1. DNA-Based Detection Finds Hidden Microbes

The GI-MAP uses quantitative PCR DNA technology, which identifies bacteria, parasites, fungi, and viruses at the genetic level. This means it can detect organisms even in very small amounts that traditional stool cultures often miss.

Why this matters for MCAS:Hidden infections—like H. pylori, Candida, or parasites—can trigger chronic immune activation and mast cell responses.

2. It Evaluates the Gut Immune System

MCAS is an immune dysregulation condition, and the GI-MAP includes markers that show how the immune system is reacting in the gut.

Important markers include:

• Secretory IgA (sIgA) – shows mucosal immune activity

• Calprotectin – indicates intestinal inflammation

• Anti-gliadin IgA – immune reaction to gluten

• Eosinophil activation protein (EDN/EPX) – linked to allergic inflammation

Why this matters for MCAS:These markers can reveal immune activation in the gut that may drive mast cell flares.

3. It Identifies Dysbiosis Linked to Mast Cell Activation

Our test measures levels of beneficial and opportunistic bacteria and shows microbiome imbalance (dysbiosis).

Why this matters:Research suggests gut dysbiosis can contribute to:

• histamine production

• intestinal inflammation

• mast cell activation

Certain bacteria can even produce histamine directly, worsening MCAS symptoms.

4. It Looks at Digestive Function and Gut Barrier Health

The GI-MAP includes markers that many other stool tests skip:

• Pancreatic elastase – digestive enzyme function

• Steatocrit (fecal fat) – fat malabsorption

• Beta-glucuronidase – detox and microbial metabolism

• Zonulin (optional) – intestinal permeability (“leaky gut”)

Why this matters for MCAS:Leaky gut and poor digestion can allow antigens and toxins into the bloodstream, triggering mast cells.

5. It Helps Identify Root Causes of Histamine Intolerance

Many people with MCAS have histamine intolerance triggered by gut issues, including:

• bacterial overgrowth

• fungal overgrowth

• H. pylori infection

• low gut immune defense

The GI-MAP can detect these contributors in a single stool test.

How It Differs From Typical Gut Tests

Typical Stool Test	GI-MAP
Often culture-based	DNA PCR technology
Usually looks only for major pathogens	Detects bacteria, parasites, fungi, viruses
Limited immune markers	Includes immune and inflammation markers
Limited microbiome analysis	Shows dysbiosis and microbial balance https://www.facebook.com/groups/1217157120332646
Less functional data	Includes digestive and gut barrier markers

Traditional tests often only identify severe infections, while GI-MAP can uncover subtle imbalances driving chronic immune symptoms.

Follow my blog to get more helpful health & healing tips, as well as more ways to increase your butyrate. 

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The Path Back to Safety is a grounded, compassionate guide for anyone living with chronic illness—especially when symptoms don’t fit neatly into a single diagnosis. Rather than treating conditions in isolation, the book explores how many chronic illnesses overlap, interact, and often stem from shared underlying patterns in the nervous system, immune system, hormones, and stress response.

It thoughtfully weaves together conditions such as chronic fatigue syndrome, fibromyalgia, long COVID, Lyme and post-viral syndromes, MCAS, POTS, dysautonomia, autoimmune and inflammatory conditions, thyroid and hormonal imbalances, connective tissue disorders like EDS, chronic pain, neurological symptoms, mast cell issues, histamine intolerance, anxiety rooted in the body, and unexplained multisystem symptoms. Through this lens, readers begin to see why treatments often fail when the body is addressed in pieces instead of as a whole.

Angela Ashton explains how these conditions frequently coexist, amplify one another, and cycle through the same pathways—nervous system dysregulation, chronic inflammation, immune overactivation, trauma responses, and loss of internal safety. The book offers clarity, validation, and a unifying framework that helps readers understand why their symptoms make sense together—and how healing becomes possible when safety, regulation, and connection are restored.

This is not a one-condition book. It’s a map for anyone whose illness has been complex, misunderstood, or labeled “too much,” offering a calm, holistic path forward when the body has been living in survival mode for far too long.

The Path Back to Safety, a grounded guide to chronic illness available on Amazon

The Path Back to Safety by Angela Ashton now available on Amazon