Gut Dysbiosis and Pulmonary Fibrosis: What Does the Evidence Show?
Pulmonary fibrosis is usually viewed as a disease centered within the lungs.
In idiopathic pulmonary fibrosis, repeated injury to alveolar epithelial cells, abnormal tissue repair, fibroblast activation and excessive deposition of extracellular matrix gradually replace normal lung architecture with scar tissue.
But researchers are increasingly asking whether factors outside the lungs may influence this process.
One of the most rapidly developing areas is the gut microbiome.
The human intestine contains trillions of microorganisms that interact continuously with the immune system, metabolism and intestinal barrier.
When this microbial ecosystem becomes disrupted—a state known as gut dysbiosis—the effects may extend far beyond the gastrointestinal tract.
This has led to growing interest in the gut–lung axis: the network of immune, metabolic and microbial signals connecting intestinal health with respiratory physiology.
Pulmonary fibrosis has now become part of this discussion.
Recent experimental studies have demonstrated changes in intestinal microbial composition, microbial metabolites and intestinal-barrier integrity during pulmonary fibrosis.
More importantly, human evidence is beginning to emerge.
In 2026, investigators analyzed the gut microbiota of 411 patients with idiopathic pulmonary fibrosis and found associations between microbial community characteristics, pulmonary disease severity and transplant-free survival.
That study represents an important step forward because it moves the gut–lung hypothesis beyond small exploratory cohorts.
However, the findings still do not prove that gut dysbiosis causes pulmonary fibrosis.
They also do not prove that correcting the microbiome can reverse or slow established fibrosis.
The current evidence therefore sits in an important middle ground:
the gut microbiome appears to be associated with pulmonary fibrosis biology, but microbiome-directed treatment remains investigational.
This article examines what the evidence actually shows.
What Is Gut Dysbiosis?
The intestinal microbiome consists of a complex ecosystem containing:
bacteria
viruses
fungi
archaea
microbial genes
microbial metabolites
These microorganisms participate in important physiological functions including:
digestion
vitamin synthesis
bile-acid metabolism
immune regulation
maintenance of the intestinal barrier
production of short-chain fatty acids
metabolism of amino acids such as tryptophan
A healthy microbiome is not defined by one universal bacterial composition.
Different healthy people may have very different microbial profiles.
Gut dysbiosis therefore does not mean the presence of one specific “bad bacteria.”
Instead, it generally refers to disruption of the microbial ecosystem.
This may include:
reduced microbial diversity
depletion of potentially beneficial organisms
expansion of pro-inflammatory or opportunistic organisms
altered microbial metabolic function
disturbed communication between microbes and the host immune system
Dysbiosis can be influenced by many factors, including:
age
diet
antibiotics
proton-pump inhibitors
chronic illness
infections
metabolic disease
intestinal motility
geography
smoking
lifestyle
This is important in pulmonary fibrosis because many patients are older, have multiple comorbidities and use medications that themselves can affect gut microbial composition.
What Is the Gut–Lung Axis?
The gut–lung axis describes bidirectional communication between the gastrointestinal and respiratory systems.
The intestine does not need to physically connect with the lungs for this communication to occur.
Signals may travel through:
systemic circulation
microbial metabolites
inflammatory cytokines
immune-cell trafficking
microbial products
A simplified model looks like this:
Diet and intestinal environment ↓ Gut microbiome ↓ Microbial metabolites and immune signals ↓ Systemic circulation ↓ Pulmonary immune cells and lung epithelium
The pathway is also bidirectional.
Severe lung disease can alter:
physical activity
diet
medication use
systemic inflammation
gastrointestinal physiology
which may in turn modify the gut microbiome.
Therefore, the gut–lung axis should not be interpreted as a simple one-way pathway in which intestinal bacteria directly cause lung disease.
Is There Evidence of Gut Dysbiosis in Pulmonary Fibrosis?
Yes.
But the quality of the evidence varies considerably.
The strongest mechanistic evidence comes from animal models.
Human studies are newer and still relatively limited.
A major 2025 review integrating clinical and preclinical evidence identified altered microbial communities in several fibrotic lung conditions, including:
idiopathic pulmonary fibrosis
silicosis
coal workers’ pneumoconiosis
The review identified five broad mechanisms through which microbial dysbiosis may influence pulmonary fibrosis:
immune dysregulation
gut–lung barrier dysfunction
sustained epithelial–mesenchymal signaling
altered autophagy
alveolar epithelial-cell injury or apoptosis
It also highlighted microbial mediators including:
short-chain fatty acids
tryptophan metabolites
lipopolysaccharide
bile-acid metabolites
The authors nevertheless emphasized that causality remains uncertain and that microbiome-directed therapy has not yet been standardized. (Frontiers)
Human Evidence in Idiopathic Pulmonary Fibrosis
Human data are particularly important because experimental pulmonary fibrosis models do not fully replicate human IPF.
One small human study published in 2024 examined the intestinal microbiome in patients with idiopathic pulmonary fibrosis.
Researchers compared patients receiving antifibrotic therapy, patients not receiving antifibrotic treatment and healthy controls.
Differences in microbial composition were identified between the groups.
This provided early evidence that human IPF is associated with measurable intestinal microbial alterations.
But the study was small.
Small cohorts can generate useful hypotheses, but they cannot determine causality or reliably establish disease-specific microbial signatures.
The evidence became substantially stronger in 2026.
The 2026 CleanUP-IPF Gut Microbiome Study
In May 2026, researchers published one of the largest human analyses of the gut microbiome in idiopathic pulmonary fibrosis to date.
The study examined fecal samples from 411 participants with IPF enrolled in the CleanUP-IPF clinical trial.
Investigators used both:
16S rRNA sequencing
shotgun metagenomic sequencing
They then assessed relationships between intestinal microbial characteristics and clinically important variables including:
lung function
disease severity
medication exposure
transplant-free survival
This study is particularly important because the sample size was far larger than previous gut microbiome studies in IPF. (PubMed)
What Did the 411-Patient Study Show?
Several findings were clinically relevant.
The intestinal microbiome was influenced by factors such as:
age
sex
proton-pump inhibitor use
This alone is important because it illustrates how strongly microbiome results can be affected by factors unrelated to the lung disease itself.
Researchers also found associations between microbial community composition and percent predicted DLCO.
DLCO reflects the lung’s ability to transfer gas and is an important physiological marker of disease severity in IPF.
Therefore, the association suggests that intestinal microbial patterns may relate to clinically meaningful pulmonary disease characteristics.
The study also identified associations between certain microbial taxa and transplant-free survival in selected treatment strata.
One unclassified genus within the Lachnospiraceae family was among the microbial features linked with survival-related outcomes.
This does not mean that Lachnospiraceae determine prognosis.
But it does suggest that the gut microbiome may contain biological information related to disease phenotype or severity.
Why This Study Matters
Until recently, much of the gut–pulmonary fibrosis discussion relied on:
animal models
small clinical cohorts
mechanistic speculation
extrapolation from other inflammatory diseases
The CleanUP-IPF analysis provides evidence from hundreds of patients with confirmed IPF.
This makes the association between the intestinal microbiome and pulmonary fibrosis harder to dismiss as a purely experimental concept.
At the same time, the study teaches another important lesson:
microbiome data are highly confounded.
Microbial composition can change with age, medications, geography, nutrition and disease severity.
Therefore, identifying a bacterium associated with IPF does not prove that the organism causes fibrosis.
Association Does Not Mean Causation
This principle is essential.
Imagine that patients with more severe IPF show lower abundance of a particular bacterial group.
Several explanations are possible.
The microbial change may contribute to disease.
Changes in metabolites or immune signaling could theoretically influence pulmonary biology.
Severe IPF may alter the microbiome.
Advanced disease can change:
physical activity
appetite
diet
medication exposure
gastrointestinal physiology
which may secondarily change microbial ecology.
Another factor may influence both.
Age or proton-pump inhibitor use could affect both clinical outcomes and intestinal microbial composition.
The relationship may be bidirectional.
Lung disease may alter the intestinal environment, while gut-derived signals may also influence systemic immune and metabolic pathways.
This fourth model may ultimately prove the most realistic.
How Could Gut Dysbiosis Influence Pulmonary Fibrosis?
Current research suggests several potential mechanisms.
1. Immune Dysregulation
The intestinal microbiome is an important regulator of immune development and immune tolerance.
Gut microorganisms interact with:
regulatory T cells
Th17 cells
dendritic cells
macrophages
B cells
innate lymphoid cells
Pulmonary fibrosis is not simply an inflammatory disease.
Nevertheless, immune signaling influences:
alveolar epithelial injury
macrophage activation
fibroblast behavior
tissue remodeling
Dysbiosis could theoretically alter these pathways.
One potential mechanism involves the balance between:
T regulatory cells and Th17 cells.
Microbial metabolites can influence this balance.
Abnormal Treg/Th17 activity has been implicated in several autoimmune and fibrotic conditions.
Whether modifying these signals will alter human IPF remains unknown.
2. Intestinal Barrier Dysfunction
The intestinal epithelium normally creates a selective barrier separating intestinal microbes from systemic circulation.
Important tight-junction proteins include:
ZO-1
occludin
claudins
Experimental pulmonary fibrosis models have demonstrated both gut microbial changes and disruption of intestinal barrier markers.
This raises the possibility that pulmonary fibrosis may be associated with increased intestinal permeability.
If the barrier becomes impaired, greater amounts of microbial material could enter systemic circulation.
This has sometimes been described as “leaky gut.”
However, the evidence needs careful interpretation.
Animal models provide biologically plausible evidence.
Direct human evidence proving that increased intestinal permeability drives idiopathic pulmonary fibrosis remains limited.
Therefore:
“Leaky gut causes pulmonary fibrosis” is not currently an evidence-based statement.
3. Lipopolysaccharide and Endotoxemia
One microbial molecule frequently discussed in gut–lung research is:
lipopolysaccharide, or LPS.
LPS is a component of the outer membrane of Gram-negative bacteria.
It can activate innate immune pathways through receptors such as:
TLR4
leading to downstream activation of pathways including:
NF-κB.
These pathways can increase inflammatory cytokine production.
TLR4-related signaling also interacts with processes involved in:
epithelial injury
fibroblast activation
extracellular matrix production
A theoretical pathway therefore looks like this:
Gut dysbiosis ↓ Barrier dysfunction ↓ Increased microbial-product exposure ↓ LPS/TLR4 signaling ↓ Systemic inflammation and pulmonary signaling
This pathway has substantial mechanistic plausibility.
But its contribution to human IPF is still uncertain.
4. Short-Chain Fatty Acids
One of the most important ways gut bacteria communicate with the host is through short-chain fatty acids, or SCFAs.
The major SCFAs are:
acetate
propionate
butyrate
They are produced when intestinal microbes ferment dietary substrates.
SCFAs can influence physiology through receptors including:
GPR41
GPR43
GPR109A
They can also influence gene expression through effects on histone deacetylase activity.
SCFAs affect:
regulatory T-cell function
macrophage behavior
intestinal barrier integrity
epithelial biology
inflammatory signaling
This makes them strong candidate mediators of the gut–lung axis.
Butyrate and Lung Fibrosis
Butyrate has received particular attention.
It is produced by several groups of anaerobic intestinal organisms, including members of:
Roseburia
Faecalibacterium
Lachnospiraceae
Butyrate supports colonocyte metabolism and intestinal epithelial integrity.
It also has immune-regulatory and epigenetic effects.
Because of these properties, researchers have proposed that depletion of butyrate-producing bacteria could theoretically reduce protective immune or barrier signaling.
Experimental antifibrotic effects involving butyrate-related pathways have also been described.
However, three concepts should not be confused.
Low abundance of butyrate-associated bacteria
does not necessarily mean:
low intestinal butyrate production
and neither automatically means:
oral butyrate supplementation will treat pulmonary fibrosis.
No adequate human clinical trial has demonstrated that butyrate supplementation slows or reverses IPF.
5. Tryptophan Metabolism
Tryptophan provides another important connection between microbiome metabolism and host immunity.
Dietary tryptophan can enter several pathways:
kynurenine metabolism
serotonin metabolism
microbial indole metabolism
Gut microorganisms can generate compounds such as:
indole derivatives
indole-3-acetic acid
related microbial metabolites
Some interact with the aryl hydrocarbon receptor, or AhR.
AhR signaling can influence:
epithelial integrity
Treg/Th17 balance
mucosal immunity
inflammatory responses
Pulmonary fibrosis research has also investigated several tryptophan-related metabolites.
Some may promote profibrotic signaling.
Others may appear protective in experimental models.
Compounds such as:
indole-3-acetic acid
5-methoxytryptophan
selected AhR ligands
have shown effects on pathways involving:
autophagy
fibroblast activation
epithelial senescence
TGF-β signaling
These are scientifically interesting findings.
They are not established treatments for pulmonary fibrosis.
6. Bile-Acid Metabolites
The intestinal microbiome plays a central role in bile-acid metabolism.
Primary bile acids produced by the liver can be modified by intestinal microorganisms.
The resulting metabolites can signal through receptors such as:
FXR
TGR5
These pathways influence:
immune activity
metabolism
epithelial function
inflammatory signaling
Recent pulmonary fibrosis reviews include altered bile-acid metabolism among the possible mechanisms connecting intestinal dysbiosis with fibrotic lung disease. (Frontiers)
The field remains early, but this supports a broader concept:
microbial function may matter more than individual bacterial names.
7. Autophagy
Autophagy is a cellular recycling process that removes damaged proteins and organelles.
It is essential for cellular homeostasis.
Impaired autophagy has been implicated in pulmonary fibrosis.
Microbial metabolites may influence signaling pathways such as:
PI3K → AKT → mTOR
which regulate autophagy.
Insufficient autophagy may:
increase epithelial vulnerability to injury
promote cellular senescence
facilitate fibroblast activation
This provides another possible route through which microbiome-related metabolites could influence fibrosis.
Most evidence in this area remains preclinical.
8. Epithelial Injury and Fibroblast Activation
Repeated alveolar epithelial injury is central to current models of IPF.
Damaged epithelial cells release signals that promote:
fibroblast recruitment
myofibroblast differentiation
collagen production
extracellular matrix deposition
One of the major signaling pathways is:
TGF-β → Smad
Experimental microbiome-targeted interventions have altered this pathway in animal models.
Recent experimental work with probiotic organisms has also reported reduced bleomycin-induced fibrosis together with changes in intestinal microbial composition and TGF-β-related signaling.
This supports mechanistic plausibility.
But once again:
a probiotic reducing fibrosis in mice is not evidence that probiotics treat IPF in humans.
9. Microbial Peptides and Direct Lung Injury
Another emerging mechanism involves microbial peptides.
The 2025 pulmonary fibrosis gut–lung review identifies corisin, a bacterial peptide, as one potential mediator capable of promoting alveolar epithelial-cell apoptosis in experimental fibrosis pathways. (Frontiers)
This is important because it expands the gut–lung discussion beyond classical metabolites.
Microbes may potentially influence lung biology through:
metabolites
structural products
peptides
immune signaling
This area requires substantially more research.
What Do Animal Models Tell Us?
Animal models provide some of the strongest mechanistic evidence supporting the gut–lung axis in pulmonary fibrosis.
Bleomycin and silica models have demonstrated:
intestinal dysbiosis
altered microbial metabolites
intestinal barrier abnormalities
changes in immune signaling
correlations between microbial profiles and fibrosis severity
Experimental manipulation of the microbiome has also altered fibrosis outcomes.
Strategies investigated include:
probiotics
prebiotics
high-fiber diets
microbial metabolites
fecal microbiota transplantation
antibiotics
experimental herbal formulations
The 2025 review concluded that several microbiome-targeted interventions have shown antifibrotic activity in experimental models. (Frontiers)
But there is a major translational limitation.
Bleomycin-induced fibrosis is not identical to human IPF.
Animal models often contain a stronger inflammatory phase and may partially resolve spontaneously.
Human IPF is a chronic, age-associated and highly heterogeneous fibrotic disease.
Therefore, experimental success cannot be assumed to translate into human treatment efficacy.
What About the Lung Microbiome?
The intestinal microbiome is only one part of the microbial story.
The lower respiratory tract also contains microbial communities.
Research in IPF has identified:
altered lung microbial composition
increased bacterial burden in some cohorts
reduced diversity
associations between pulmonary bacterial burden and disease outcomes
This raises the possibility that several microbial ecosystems interact in pulmonary fibrosis.
A broader model may involve:
oral microbiome ↕ lung microbiome ↕ pulmonary immunity ↕ systemic circulation ↕ gut microbiome
The gut and lung microbiomes should therefore not be treated as interchangeable.
Could Oral Health Matter?
Potentially.
The lungs are continually exposed to microorganisms originating from the upper airway.
Microaspiration of oral secretions occurs even in healthy people.
Oral microbial communities may therefore influence the lower-airway microbiome.
Poor oral health, periodontal disease, aspiration risk and altered swallowing may all theoretically affect respiratory microbial ecology.
However, oral-health interventions have not been proven to modify the progression of IPF.
This remains another emerging area of investigation.
Gut Dysbiosis in Other Fibrotic Lung Diseases
The gut–lung hypothesis extends beyond idiopathic pulmonary fibrosis.
Microbial alterations have also been reported in conditions including:
silicosis
coal workers’ pneumoconiosis
systemic sclerosis-associated ILD
rheumatoid arthritis-associated ILD
myositis-associated ILD
This suggests that gut–immune interactions may influence fibrosis across multiple disease categories.
However, the underlying mechanisms of these diseases differ.
It would therefore be inappropriate to assume that one microbial pattern or treatment applies to all forms of pulmonary fibrosis.
Autoimmune ILD May Be Especially Relevant
Autoimmune-associated ILD may be particularly interesting from a microbiome perspective because the microbiome is already known to influence systemic immune regulation.
Recent human studies have identified microbiome differences in:
systemic sclerosis-associated ILD
rheumatoid arthritis-associated ILD
myositis-associated ILD
For example, a multinational systemic sclerosis study involving 285 patients demonstrated a distinct gut microbial signature in SSc-ILD and relationships between microbial pathways and radiological ILD extent.
These studies strengthen the concept of a broader:
gut–immune–lung axis
rather than a purely gastrointestinal explanation for disease.
Is Gut Dysbiosis the Same as SIBO?
No.
This distinction is clinically important.
Gut dysbiosis refers broadly to disruption of microbial ecology.
SIBO refers specifically to abnormal microbial overgrowth or composition within the small intestine.
A person can have dysbiosis without SIBO.
A stool microbiome test also does not diagnose SIBO.
Breath testing is typically used clinically when SIBO is suspected.
SIBO may be particularly common in systemic sclerosis because of intestinal dysmotility, but it is not currently established as a cause of idiopathic pulmonary fibrosis.
Is Dysbiosis the Same as “Leaky Gut”?
No.
These concepts overlap but are not synonymous.
Dysbiosis refers to altered microbial ecology.
Increased intestinal permeability refers to altered intestinal-barrier function.
One may contribute to the other.
But a person may have one without clear evidence of the other.
Both have been investigated experimentally in pulmonary fibrosis.
Neither has yet been established as a routine clinical biomarker for IPF.
Can Gut Dysbiosis Cause Pulmonary Fibrosis?
At present:
we do not know.
The evidence increasingly supports an association.
Animal models support mechanistic plausibility.
Human observational studies are becoming stronger.
But human causality has not been demonstrated.
To establish causality, researchers would ideally need to show that:
dysbiosis develops before fibrosis
specific microbial changes predict disease progression
correcting those abnormalities changes clinically meaningful lung outcomes
That evidence does not yet exist.
Can Treating Gut Dysbiosis Treat Pulmonary Fibrosis?
There is currently no microbiome-directed therapy proven to treat IPF.
This includes:
probiotics
prebiotics
synbiotics
butyrate supplements
FMT
commercial microbiome protocols
elimination diets
No adequately powered human trial has demonstrated that these interventions reliably:
improve FVC
improve DLCO
reverse HRCT fibrosis
prevent progressive pulmonary fibrosis
reduce mortality
This is one of the most important clinical points for patients to understand.
Probiotics and Pulmonary Fibrosis
Probiotics have generated substantial research interest.
Selected probiotic strains can influence:
gut microbial composition
immune signaling
barrier function
microbial metabolite production
Animal pulmonary fibrosis studies have demonstrated antifibrotic effects with certain specific strains.
However, probiotic effects are highly strain-specific.
The effect of one strain cannot automatically be generalized to another.
More importantly, no probiotic strain has been established as a disease-modifying treatment for human IPF.
Prebiotics, Fiber and the Microbiome
Prebiotics provide substrates that can support selected microbial populations.
Dietary fiber can increase microbial fermentation and influence SCFA production.
This is biologically attractive.
But the clinical interpretation requires caution.
There is no evidence that a high-fiber diet reverses pulmonary fibrosis.
And some patients with fibrotic lung disease may also have:
bloating
SIBO
intestinal dysmotility
severe reflux
systemic sclerosis
reduced appetite
malnutrition
Therefore, dietary recommendations should be individualized.
What About Butyrate Supplements?
Butyrate has promising mechanistic properties.
But mechanistic plausibility is not the same as clinical efficacy.
At present, butyrate supplementation has not been demonstrated to:
improve FVC
slow IPF progression
reverse fibrosis
improve survival
Therefore, butyrate should be regarded as an experimental research target rather than an established IPF therapy.
What About Fecal Microbiota Transplantation?
FMT can substantially alter gut microbial composition.
Its strongest established clinical role is in selected patients with recurrent Clostridioides difficile infection.
Animal studies have investigated FMT in pulmonary fibrosis and other lung conditions.
Some have shown reductions in inflammation or fibrosis.
However, FMT has not been established as treatment for human pulmonary fibrosis.
It should not currently be used for IPF outside an appropriate research context.
What About Antibiotics?
Antibiotics are particularly interesting because early lung microbiome research raised the possibility that altering microbial burden might influence IPF outcomes.
The CleanUP-IPF trial itself examined antimicrobial treatment.
However, broad antimicrobial therapy has not become an established disease-modifying strategy for IPF.
This illustrates an important principle:
changing microbial abundance is not necessarily the same as correcting microbial function.
Future treatment may require more precise approaches.
Could Diet Modify the Gut–Lung Axis?
Yes, diet can modify the microbiome.
It influences:
microbial diversity
substrate availability
SCFA production
bile-acid metabolism
host metabolic health
But no specific “pulmonary fibrosis microbiome diet” has been clinically validated.
A useful nutritional strategy should instead focus on:
adequate protein
preservation of muscle
appropriate calories
diverse nutrient intake
metabolic health
gastrointestinal tolerance
The objective should not simply be “feeding good bacteria.”
Nutrition and Muscle Mass Matter in ILD
Patients with interstitial lung disease can develop:
weight loss
reduced appetite
sarcopenia
reduced exercise tolerance
frailty
These factors may influence clinical outcomes independently of microbiome biology.
Therefore, any gut-directed intervention that causes unnecessary dietary restriction may actually be harmful.
Maintaining muscle mass and nutritional adequacy should remain a priority.
What About GERD and Microaspiration?
Gastroesophageal reflux is common in IPF.
The potential pulmonary mechanism differs from the gut–lung microbiome pathway.
Reflux may theoretically affect the lungs through:
reflux → microaspiration → repeated epithelial exposure
The gut–lung axis instead involves:
gut microbes → metabolites and immune signaling → systemic circulation → lung
These pathways may coexist.
But they should not be treated as the same mechanism.
Current IPF guidelines do not recommend antacid therapy solely to improve respiratory outcomes.
Symptomatic GERD should still be treated according to standard clinical indications.
Can Improving Gut Health Still Benefit Someone With Pulmonary Fibrosis?
Potentially, yes.
But the goals need to be realistic.
A patient with pulmonary fibrosis may also have:
reflux
constipation
diarrhea
persistent bloating
nutritional deficiencies
weight loss
SIBO
medication-related GI symptoms
Appropriate assessment and treatment of these conditions may improve:
quality of life
food tolerance
nutritional intake
bowel function
symptom burden
Those benefits matter even if lung fibrosis itself does not change.
Should Patients With Pulmonary Fibrosis Have Commercial Microbiome Testing?
Not routinely for the purpose of managing pulmonary fibrosis.
Commercial stool testing currently cannot determine:
whether dysbiosis caused IPF
whether fibrosis will progress
whether antifibrotic treatment is required
whether a specific organism is causing lung fibrosis
which probiotic will improve FVC
Research metagenomics and commercial stool analysis are not equivalent.
Pulmonary fibrosis treatment decisions should remain based on established clinical assessment.
What Tests Actually Matter in Pulmonary Fibrosis?
Depending on the type of ILD, clinically relevant evaluation may include:
high-resolution CT
pulmonary function testing
DLCO
autoimmune serology
exposure assessment
oxygenation
multidisciplinary ILD review
echocardiography or pulmonary hypertension assessment when appropriate
lung transplantation evaluation in advanced disease
Microbiome testing currently does not replace any of these.
Functional and Integrative Medicine Perspective
The growing gut–lung evidence provides an opportunity for a more comprehensive approach to pulmonary fibrosis.
It does not justify replacing established pulmonary medicine.
A clinically responsible integrative assessment can consider:
gastrointestinal symptoms
reflux
bowel function
nutritional status
muscle mass
metabolic health
physical activity
sleep
environmental exposures
medication effects
Where appropriate, specific gastrointestinal problems such as SIBO or malabsorption may also be evaluated.
The key is to distinguish:
clinically useful supportive care
from:
unproven claims that treating the microbiome reverses fibrosis.
What We Know
Current evidence supports the following conclusions:
the gut and lung communicate through immune and metabolic pathways
intestinal dysbiosis occurs in experimental pulmonary fibrosis
human IPF is associated with measurable gut microbial differences
a 2026 study involving 411 patients identified associations between gut microbiota and pulmonary disease severity
microbial characteristics were associated with DLCO
selected microbial features were associated with transplant-free survival
SCFAs, tryptophan metabolites, LPS and bile-acid metabolites are plausible biological mediators
experimental manipulation of the microbiome can modify fibrosis in animal models
The gut microbiome is therefore a credible pulmonary fibrosis research target. (PubMed)
What We Do Not Know
Important uncertainties remain.
We do not yet know:
whether gut dysbiosis causes IPF
whether microbial changes occur before disease begins
whether dysbiosis predicts progression independently of other risk factors
whether correcting dysbiosis slows FVC decline
whether probiotics improve pulmonary outcomes
whether butyrate supplementation helps IPF
whether FMT is beneficial
whether commercial stool testing can guide pulmonary treatment
which microbial pathways are causal rather than simply associated with disease
These are major unanswered questions.
What Does This Mean for Patients?
The practical message should be balanced.
Gut health matters.
But gut treatment is not a replacement for pulmonary fibrosis treatment.
If a patient with IPF or another fibrotic ILD has gastrointestinal symptoms, those symptoms deserve appropriate evaluation.
Attention to:
nutrition
reflux
bowel function
weight
muscle mass
metabolic health
can be part of comprehensive care.
At the same time, established pulmonary management remains central.
Depending on diagnosis and disease stage, this may include:
antifibrotic treatment
immunomodulatory therapy for autoimmune ILD
pulmonary rehabilitation
oxygen therapy
vaccination
management of comorbidities
transplant evaluation
Where Is Gut–Lung Research Going Next?
The field is moving beyond simply asking:
Which bacteria are increased or decreased?
Future research will probably integrate:
**metagenomics
metabolomics
immune profiling
pulmonary function
HRCT progression
longitudinal outcomes**
This may help researchers identify:
microbial pathways associated with progression
metabolites that influence fibrotic biology
patient subgroups with different microbial phenotypes
biomarkers that predict outcome
therapeutic targets
Future strategies could potentially include:
precision probiotics
defined microbial consortia
targeted prebiotics
postbiotics
microbial metabolites
engineered organisms
individualized nutrition
But these interventions need rigorous clinical testing.
What Would a Successful Microbiome Trial Need to Show?
A meaningful pulmonary fibrosis microbiome trial should not simply report that the stool microbiome changed.
It should demonstrate improvement in clinically relevant outcomes such as:
FVC decline
DLCO
HRCT progression
exercise capacity
quality of life
hospitalization
transplant-free survival
Only then could microbiome modification begin to be considered a genuine pulmonary therapeutic strategy.
Frequently Asked Questions
Can gut dysbiosis cause pulmonary fibrosis?
It has not been proven.
Gut dysbiosis is associated with pulmonary fibrosis in experimental studies and emerging human research, but causality in humans remains uncertain.
Is the gut microbiome different in people with IPF?
Yes.
Several studies have reported differences in intestinal microbial composition in IPF.
The strongest recent human evidence comes from a 2026 study of 411 patients showing associations between gut microbiota, DLCO and transplant-free survival. (PubMed)
Can probiotics reverse pulmonary fibrosis?
No.
No probiotic has been proven to reverse or stop human pulmonary fibrosis.
Animal studies are promising but are not sufficient to establish treatment efficacy.
Does butyrate help pulmonary fibrosis?
Butyrate has biologically interesting immune and epigenetic effects and has been studied experimentally.
However, butyrate supplementation has not been shown in clinical trials to treat IPF.
Is leaky gut linked to pulmonary fibrosis?
Animal pulmonary fibrosis models demonstrate intestinal-barrier abnormalities.
Direct human evidence proving that increased intestinal permeability drives IPF is still limited.
Is SIBO associated with pulmonary fibrosis?
SIBO may occur in patients with conditions such as systemic sclerosis because of intestinal dysmotility.
It has not been established as a cause of idiopathic pulmonary fibrosis.
Should I have a stool microbiome test if I have pulmonary fibrosis?
Not routinely for the purpose of managing the lung disease.
Commercial microbiome testing cannot currently predict IPF progression or determine antifibrotic therapy.
Can diet improve the gut microbiome in pulmonary fibrosis?
Diet can certainly influence intestinal microbial composition.
However, there is no specific microbiome diet proven to reverse pulmonary fibrosis.
Nutrition should focus on adequacy, muscle preservation and individual gastrointestinal tolerance.
Is the lung microbiome different from the gut microbiome?
Yes.
They are distinct microbial ecosystems.
Both are being investigated in pulmonary fibrosis and may communicate through immune and metabolic pathways.
Could future microbiome treatments help pulmonary fibrosis?
Possibly.
The field is investigating microbial metabolites, probiotics, prebiotics, FMT and other targeted strategies.
At present, these remain experimental for pulmonary fibrosis.
Key Takeaway
The evidence can be summarized in one sentence:
Gut dysbiosis is increasingly associated with pulmonary fibrosis, and several biologically plausible gut–lung mechanisms have been identified, but we do not yet know whether dysbiosis causes human IPF or whether modifying the microbiome can improve pulmonary outcomes.
That distinction is essential.
Conclusion
The relationship between gut dysbiosis and pulmonary fibrosis has moved from a speculative concept into a legitimate area of pulmonary research.
Preclinical studies demonstrate that pulmonary fibrosis can be accompanied by changes in:
intestinal microbial composition
microbial metabolites
intestinal barrier integrity
immune signaling
Mechanistic research suggests that the gut microbiome may influence pulmonary biology through pathways involving:
short-chain fatty acids
tryptophan metabolism
lipopolysaccharide
bile acids
immune regulation
autophagy
epithelial injury
fibroblast activation
Human evidence is also becoming stronger.
Most importantly, the 2026 CleanUP-IPF microbiome analysis involving 411 patients with idiopathic pulmonary fibrosis demonstrated associations between intestinal microbial characteristics, pulmonary disease severity and transplant-free survival. (PubMed)
That does not prove causation.
But it does provide clinically meaningful evidence that the intestinal microbiome is connected with the biological phenotype of IPF.
The critical question now is no longer simply:
“Is the gut microbiome different in pulmonary fibrosis?”
Increasing evidence suggests that it is.
The more important questions are:
Do those microbial changes contribute to disease progression?
Which microbial metabolites actually influence fibrotic pathways?
Can changing the microbiome improve meaningful pulmonary outcomes?
Until those questions are answered, microbiome-directed therapy should remain investigational.
For patients, gastrointestinal symptoms, nutrition, reflux, metabolic health and muscle preservation can still be appropriately addressed as part of comprehensive care.
But these strategies should complement—not replace—evidence-based pulmonary treatment.
The future of the field may ultimately lie not in a generic concept of “healing the gut,” but in identifying specific microbial functions, metabolites and host–microbe interactions that influence fibrotic disease.
That is where gut–lung science may eventually become clinically actionable.
About Dr. Samar Shadly
Dr. Samar Shadly is a Consultant Pulmonologist and Certified Functional Medicine Practitioner, with advanced subspecialty training in interstitial lung disease, pulmonary fibrosis, pulmonary hypertension and lung transplantation at the University of Toronto.
Her clinical and academic interests include Integrative and Functional Pulmonology, the gut–lung axis, pulmonary fibrosis, autoimmune-associated interstitial lung disease, nutrition, metabolic health and emerging microbiome science.
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If you are living with pulmonary fibrosis or another form of interstitial lung disease and would like a comprehensive assessment that considers your pulmonary disease together with relevant gastrointestinal, nutritional, metabolic and lifestyle factors, you can explore the available online consultation options.
The purpose of an integrative assessment is not to replace established pulmonary treatment, but to identify additional areas of health that may be relevant to symptoms, resilience and overall well-being.
Contact us through the consultation page or WhatsApp to learn more about online consultation options.
Functional and integrative care is intended to complement—not replace—appropriate pulmonary treatment, including antifibrotic or immunomodulatory therapy when indicated.
Medical Disclaimer: This article is provided for educational purposes only and does not constitute individualized medical advice. Patients with pulmonary fibrosis or interstitial lung disease should remain under appropriate specialist pulmonary care.
Related Topics:
Gut–Lung Axis and Pulmonary Fibrosis: Can Gut Health Affect Lung Fibrosis?
Leaky Gut and Pulmonary Fibrosis: Is There Scientific Evidence?
SCFAs and Pulmonary Fibrosis
Butyrate and Lung Fibrosis
Tryptophan Metabolism and Pulmonary Fibrosis
Probiotics and Pulmonary Fibrosis
Gut Microbiome and Interstitial Lung Disease
Gut Microbiome and Systemic Sclerosis–Associated ILD
GERD, Microaspiration and Pulmonary Fibrosis
References
Kim JS, Loe A, Ma SF, et al. Gut microbiota associate with disease severity and survival in idiopathic pulmonary fibrosis. Am J Respir Crit Care Med. Published online May 19, 2026. doi:10.1093/ajrccm/aamag249.
Yang J, Wang J, Li J, Yang S. Lung-gut axis, intestinal microbiota, and pulmonary fibrosis: mechanisms and therapeutic potential. Front Microbiol. 2025;16:1711299. doi:10.3389/fmicb.2025.1711299.
Gut microbiota profiles of patients with idiopathic pulmonary fibrosis. Experimental Lung Research. 2024.