why do I keep getting lung & respiratory infections – the gut connection nobody mentions

Do you have recurrent chest infections, sinusitis that won't fully clear, bronchitis or pneumonia that returns every winter, or respiratory symptoms that linger long after everyone else has recovered, perhaps even for months?

If this is a familiar pattern — and especially if antibiotics keep being prescribed without breaking the cycle — the gut is almost certainly part of the picture. And it's almost certainly not being looked at.

the gut-lung axis — what it is & why it matters

The gut and lungs are in constant two-way communication through the immune system, the bloodstream, and the microbiome. This bidirectional relationship is called the gut-lung axis — and it fundamentally changes how recurrent respiratory illness should be understood.

70-80% of all immune cells in the human body are located in the gut. This makes the gut the primary site where the immune system is educated, trained, and calibrated. What happens in the gut directly shapes how well the respiratory tract can defend against infection, recover from illness, and prevent recurrence.

A healthy, diverse gut microbiome produces short-chain fatty acids (SCFAs) — compounds including acetate, propionate, and butyrate — that travel via the bloodstream to the lungs. There they strengthen the epithelial barrier, prime antiviral defences, activate immune cells, and regulate inflammatory responses. The gut is effectively producing the raw materials the lungs need to fight infection.

When the gut microbiome is disrupted — through dysbiosis, poor diet, chronic stress, repeated antibiotic use, or ageing — this production breaks down. The lungs receive less immune support. Antiviral defences weaken. The inflammatory tone of the respiratory tract increases. The mucosa becomes more susceptible to colonisation. And recurrent respiratory infections begin to make biological sense.

how a lung infection disrupts the gut — & vice versa

This axis doesn't just run one way. Lung infections actively disrupt the gut — and gut dysfunction actively worsens respiratory illness. The bidirectional nature is what creates the cycle.

When a viral lung infection occurs, it triggers systemic inflammation, reduced appetite, and decreased oxygen delivery — all of which alter gut microbial balance and compromise the gut epithelial barrier. This disruption then reduces the gut's capacity to produce the immune-supporting metabolites the lungs need to recover — making secondary infections more likely and recovery slower.

Conversely, gut dysbiosis shifts the body toward a chronic pro-inflammatory state — increasing circulating cytokines that predispose the respiratory tract to exaggerated immune responses and tissue damage during infection. The gut is setting the inflammatory tone for the whole system. When that tone is already elevated, respiratory infections become more severe.

Microbes also transfer directly between the two organs. Swallowing infected sputum moves respiratory microbes into the gut. Microaspiration brings gut contents into the airways. These physical transfers can alter local microbiota at the destination — triggering further inflammation, dysbiosis, or secondary infection.

how antibiotics make the cycle worse

This is the uncomfortable part of the conversation — because the standard response to recurrent respiratory infections is repeated antibiotic prescriptions. And antibiotics are a significant driver of the gut disruption that perpetuates the cycle.

Most URTIs and many lower respiratory tract infections are viral. Antibiotics do not treat viral infections. Yet in developed countries, URTIs alone account for 75% of all antibiotic prescriptions. A 2026 Australian Centre for Disease Control report found critical antibiotic resistance rose 25% in 2024.

Beyond the resistance issue — broad-spectrum antibiotics indiscriminately deplete both harmful and beneficial gut bacteria, reducing the microbial diversity that supports immune function. This impairs SCFA production, weakens mucosal immunity, reduces secretory IgA — the antibody that lines respiratory surfaces and blocks pathogen colonisation — and leaves the gut-lung axis less capable of defending against the next infection.

The antibiotic prescribed for the respiratory infection depletes the gut bacteria needed to prevent the next one. Each course compounds the microbiome disruption. The cycle tightens.

Research shows that people with recurrent URTIs have characteristic dysbiosis patterns — reduced Bifidobacterium and Lactobacillus strains, lower SCFA-producing (gut lining and immune supportive) bacteria. Treating the infection without addressing this underlying microbiome imbalance means the vulnerability remains intact.

what dysbiosis does to respiratory defences specifically

Gut dysbiosis impairs three key defences against respiratory infection

1. Antiviral defence – A healthy microbiome primes interferon responses and activates natural killer cells and alveolar macrophages. Dysbiosis reduces the production of desaminotyrosine and SCFAs — leaving the lungs less prepared to combat viral entry and replication.

2. Inflammatory tone – Dysbiosis shifts the gut toward a pro-inflammatory state, increasing circulating TNF-α, IL-6, and IL-17. This chronic low-grade inflammation predisposes the respiratory tract to exaggerated immune responses and tissue damage during infection — making each illness more severe and recovery slower.

3. Mucosal immunity – Beneficial gut bacteria stimulate T-regulatory cells and secretory IgA production. When dysbiosis occurs, IgA secretion drops and the respiratory mucosa becomes more susceptible to pathogen colonisation. This is the immune layer that stops respiratory pathogens gaining a foothold in the first place.

bacteria linked to respiratory infections

Certain bacteria that proliferate in a dysbiotic gut — including Klebsiella pneumoniae, Pseudomonas aeruginosa, and Streptococcus pneumoniae — can translocate via the gut-lung axis and directly contribute to pneumonia and other serious respiratory infections. This is one reason gut dysbiosis is not merely associated with lung vulnerability — in some cases it is actively seeding it.

practical steps — what the research supports

Dietary foundations

A diet rich in diverse plant fibres and fermented foods supports SCFA production and microbiome diversity — which directly feeds the gut-lung axis. So does good fat eg from clean fatty fish. The Mediterranean dietary pattern specifically is associated with stronger immune regulation and lower infection risk. Processed foods, processed seed oils, and diets high in refined carbohydrates and sugar are associated with microbiome imblances (dysbiosis) and increased inflammatory tone.

Targeted probiotic strains

Strain specificity matters significantly here — generic probiotics often miss the mark. Research-supported strains for respiratory protection include:

• Bifidobacterium animalis subsp. lactis Bl-04 — associated with 25-40% reduction in URTI risk and delayed illness onset in healthy adults

• Bifidobacterium bifidum R0071 — significantly increased healthy days and reduced cold/flu symptoms, particularly in stressed individuals

• Lactobacillus rhamnosus R0011 & L. helveticus R0052 — support microbiome recovery following antibiotic use

For preventive respiratory protection — starting targeted probiotics 10-14 days before winter or anticipated high-risk periods has the strongest evidence. If antibiotics are genuinely necessary — starting probiotics within 48 hours of the antibiotic course significantly improves microbiome recovery outcomes.

Addressing chronic stress

Stress directly increases gut permeability and disrupts microbiome composition through well-documented physiological mechanisms — and this directly undermines the gut-lung axis. Managing stress is not a lifestyle suggestion in this context. It is mechanistically relevant to respiratory resilience.

Sleep

Sleep deprivation independently suppresses immune function and increases gut permeability. Prioritising sleep quality — not just duration — is part of rebuilding the gut-lung axis.

Micronutrient support

Vitamin C combined with probiotics has been used to reduce respiratory tract infection incidence. Vitamin D, zinc, and magnesium each support both gut barrier integrity and immune function in ways directly relevant to respiratory health.

the pattern worth recognising

If recurrent lung or respiratory infections are part of the picture — chest infections that keep returning, sinusitis that never fully clears, lingering post-viral respiratory symptoms, a feeling that immunity has become fragile — the gut-lung axis is worth investigating.

The question to ask is not only "what infection is this" — but "why is the body susceptible to this repeatedly, and what has been depleted in the gut that normally prevents it."

That question has a very different answer — and a very different approach — to another antibiotic prescription.

Nore Hoogstad is a Functional Nutritionist & Psych-K Practitioner specialising in complex, unresolved health cases. A free 20-minute call is available — come and tell the story. Book here.

SOURCES

Educational content — not medical advice. Sources: Medicine BioCeuticals, "The Gut-Lung Axis: Reducing URTIs Through Microbiome Support," Claudia Vidor BHSc Nut D Med, 2026; Australian Centre for Disease Control 2026; multiple peer-reviewed references cited therein.