The Gut-Lung Connection: The Overlooked Link

One of the biggest concerns I have about the way health and medicine are often thought about in the modern world is that we miss a lot of important connections. Gradually, some of these have become better known: for example, the gut-brain axis has (finally!) gotten some well-deserved attention over the last decade. 

Today, I want to talk about another connection that is just as intricate but still commonly overlooked: the gut-lung axis. 

These two organs communicate back and forth—what’s happening in the gut can affect the lungs, and what’s happening in the lungs can affect the gut. 

Let’s explore what this means for your health, how gut imbalances can worsen respiratory conditions and viral infections including COVID-19, and how to support a strong and healthy gut-lung axis. 

How Your Gut and Lungs Communicate

The gut-lung axis refers to the bidirectional communication network between the gut and the lungs. There are several different ways in which the two organs communicate: 

• Immune signaling: Gut-derived immune cells regulate inflammation and immune system responses throughout the body including in the lungs.
• Metabolic communication: Healthy gut bacteria produce metabolites including short-chain fatty acids (SCFAs), such as butyrate and propionate, which can enter the lungs via circulation. (1) These metabolites work to modulate inflammation and strengthen the mucosal barriers that protect both the intestinal and respiratory linings. (2)
• Neural pathways: The vagus nerve, which connects the gut and the brain, also connects both with the lungs. (3) Via this connection, neurotransmitters produced in the gut can transmit chemical messages that can influence respiratory function. 

The Lung Microbiome and the Gut Microbiome 

Many people are by now familiar with the concept of the gut microbiome: a complex ecosystem of bacteria and other microbes that live in the gut and strongly influence both digestive and overall health. 

It was discovered only recently that the lungs have their own microbiome, though it is much less complex and populated than the microbial community in the gut. (4) The lung microbiome is in communication with the gut microbiome, but in the case of some pulmonary conditions the gut microbiome itself may still be more influential. 

Gut Dysbiosis and Respiratory & Pulmonary Illness 

Research has consistently linked gut dysbiosis (an imbalance between beneficial and harmful bacteria in the gut) to the development and worsening of respiratory conditions including asthma, chronic obstructive pulmonary disease (COPD), tuberculosis, and viral infections such as COVID-19. 

Children with asthma often have lower levels of healthy gut bacteria, and asthmatic children with lower levels of beneficial gut bacteria including Bifidobacterium and Bacteroides species have a higher risk of developing allergic inflammation later in life. (5) Backing up further, studies have also found that gut dysbiosis early in life may increase the risk of developing asthma over time. (6) 

In COPD, distinct gut microbial patterns of imbalance are correlated with more severe disease. (7) Imbalances in the gut microbiome are also linked to lung cancer and cystic fibrosis. (8) In the case of COVID-19, those with more severe illness may be more likely to have gut and lung dysbiosis. (3) 

Patients with pneumonia also often have low levels of certain beneficial gut bacteria (Firmicutes and Bacteroidetes), and an overgrowth of others (Proteobacteria and Enterobacteriaceae). (9) These imbalances lead to reduced SCFA levels (SCFAs are a type of postbiotic: a beneficial waste product produced by beneficial bacteria). 

SCFAs normally help to regulate inflammation in (and outside of) the lungs and keep the immune response in check. (10) When SCFA production drops, the immune response can become overactive, fueling the cytokine storm that can make pneumonia life-threatening. 

Lung infections can also begin in the gut. When the intestinal barrier is damaged or permeable (leaky gut), bacterial fragments can enter the bloodstream and travel to the lungs, triggering inflammation and impairing immune function there. Over time, this chronic inflammatory state can lead to more frequent respiratory infections and more challenging recovery. 

Lung Inflammation and Gut Health

The gut-lung axis is bidirectional. Just as gut health influences lung health, lung inflammation can disrupt balance within the gut. For example, influenza, COVID-19, and other viral respiratory infections may trigger changes to the balance of the gut microbiome. (11, 12) 

Research on influenza and bacterial pneumonia have shown that pulmonary infections can increase intestinal permeability, allowing microbial toxins to circulate and increasing systemic inflammation. This creates a vicious cycle of inflammation coming from both the gut and the lungs. 

Lifestyle and Environmental Factors That Disrupt Gut-Lung Health

There are many factors that can negatively influence the gut-lung axis. Some key disruptors may include: 

• Antibiotics: While they’re sometimes necessary, antibiotics wipe out microbial diversity in the gut, impairing immune system function and weakening our defenses against viral lung infections. There is sometimes a vicious cycle created when antibiotics are used for chronic respiratory infections, disrupting gut bacteria balance which in turn weakens lung and immune health, making an individual more susceptible to future infections. 
• Diets low in fiber: A diet containing insufficient fiber deprives gut microbes of the nutrients they need to produce enough SCFAs. 
• Chronic stress: Chronic stress alters gut microbial balance and can trigger or exacerbate chronic inflammation. 
• Environmental toxins: Toxins from mold, air pollution, chemicals, and other sources can negatively impact both gut and lung health. 

How To Support the Gut-Lung Axis 

To restore and strengthen the health of the gut-lung axis, I like to focus on holistic, non-invasive diet and lifestyle interventions, along with strategic supplements that are supported by research. Here are some of the most simple and effective steps you can take for general support. 

Feed Your Microbiome 

A diet rich in prebiotic fibers and polyphenol-rich plant foods feeds beneficial bacteria and boosts SCFA production. (13) A high fiber diet has been linked to a reduction in mortality from respiratory disease. (14) Research also suggests that a high fiber diet may help to reduce the risk of getting influenza by supporting immune function, and dietary fibers have been shown to significantly reduce allergic airway inflammation. (15, 16) And a healthy diet overall may reduce the risk of developing COPD and other lung disorders. 

Some of the best options to include in your diet (as long as you tolerate them) include artichokes, asparagus, onions, garlic, flaxseeds, berries, and green tea. 

Rebuild the Microbiome

Probiotic supplements have been shown to help reduce airway inflammation and improve immune system resilience and lung health, as well as supporting gut health overall. (17, 18) 

Researchers have also demonstrated improvements in the duration and severity of COVID-19 and pneumonia, the prevention of allergic asthma and upper respiratory tract infections, and symptoms of cystic fibrosis with probiotic supplementation. (19 – 23) Given the immune system connection, there are many possible uses of probiotics for different kinds of lung disease, and research is ongoing. (24) 

Early stage research also shows promise with using fecal microbiota transplantation (FMT), or the transfer of a healthy microbiota from a donor to a dysbiotic individual, for respiratory and pulmonary conditions including COPD and cystic fibrosis. (25, 26) However, this would not be a first line recommendation for general gut-lung axis support. 

Supplemental postbiotics (which can include SCFAs) to support the gut-lung axis are also a newer subject of research and may offer several benefits for respiratory and pulmonary disease. (27) 

READ MORE: What Are Postbiotics And Why Do They Matter For Gut Health? 

Heal the Gut Barrier

To support the integrity of the intestinal lining, I often recommend supplemental nutrients including zinc, glutamine, and omega-3 fatty acids. These supports can help to reduce inflammation and protect the lungs by extension. 

Be Cautious With Antibiotic Use

Avoid unnecessary antibiotics in order to preserve microbial diversity. If antibiotics are needed, make sure to supplement with probiotics both during and afterwards in order to help restore balance. 

Support the Vagus Nerve and a Healthy Stress Response

Prioritize mind-body practices, which may include meditation, deep breathing, EMDR, and/or vagal nerve stimulation in order to enhance gut motility, immune regulation, and the health of the gut-lung connection. 

Everything Is Connected

The gut microbiome is the foundation of your immune system, and is connected to every other system and organ in the body, including the lungs. If you’ve been experiencing recurrent respiratory infections, chronic inflammation, or lingering symptoms after viral illness, it may be time to support your gut more deeply. 

A whole body-healing approach that emphasizes food, lifestyle, and microbiome support can help you repair and thrive. 

As one of the first functional medicine telehealth clinics in the world, we provide webcam health consultations for people around the globe.

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