A Healthy Gut to Help Combat COVID

Clinical trials are currently underway to determine if probiotics can help reduce the severity of COVID-19 and improve recovery, as your gut microbiota plays an important role in your overall health. In the past months, doctors and researchers have also discovered that people with poor gut health have a higher risk of severe illness from COVID-19.

As well as influencing digestion and immunity, scientists have discovered you have a gut-brain axis and a gut-lung axis. The gut-brain axis has bidirectional communication, through which microbiota help regulate brain function.

For example, a study1 published in 2017 found Bifidobacterium breve strain A1 helps to reduce cognitive dysfunction that is normally induced by amyloid-beta in Alzheimer’s disease.

In another study,2 researchers found a connection between an imbalanced gut microbiome and the development of amyloid plaques in the brain. More recently, researchers have discovered that there is also a gut-lung axis,3 which supports the role your microbiota plays in your immune system, both locally and systemically.

Although your gut and lungs are anatomically distinct, there is growing evidence that communication between the systems helps maintain homeostasis of your immune system. Building on this knowledge, researchers are now investigating a potential and likely link between the health of your gut microbiome and the potential risk for more severe illness from COVID-19.4

Poor Gut Health Is Connected to Severe COVID-19

A review of more than 1,000 patient records showed those who presented at admission to the hospital with gastrointestinal (GI) symptoms and suspected COVID-19 infection had worse outcomes than those without GI symptoms. The review was done at Rush University Medical Center in Chicago and ranked patients with a score of zero to three.

Even after adjusting for comorbidities, demographics and other clinical symptoms, the results held. One of the researchers from Rush University spoke with a journalist from MedPage Today, saying:5

“We knew that GI symptoms could be part of the infection but we did not know if they made a difference and conferred higher risk. So we wanted to look into the impact of initial GI symptoms to see if they might coincide with more serious disease and we found that those with GI symptoms also had established risk factors for severity, such as older age, diabetes, obesity, and hypertension.”

Of the patients evaluated, 22.4% reported experiencing at least one GI symptom, the most common of which was nausea and vomiting. Researchers also found those with GI symptoms had a higher body mass index, a higher prevalence of diabetes and high blood pressure, and were older. Although this group had a higher rate of ICU admission and intubation, the study did not look at the mortality rate.

The Centers for Disease Control and Prevention6 has also found that while the symptoms of COVID-19 will vary, over the course of the illness many people experience respiratory symptoms, fever, loss of taste and smell and gastrointestinal symptoms. This indicates GI symptoms are among those commonly reported to the CDC.

SciTech Daily7 reports that autopsy results and studies have suggested a sizable number of people with severe COVID-19 also have gastrointestinal problems. A paper published in January 2021, suggests the GI symptoms that predict severe COVID-19 are triggered by poor gut health.8

Heenam Stanley Kim, Ph.D., from Korea University examined the evidence and proposes that gut dysbiosis can exacerbate the severity of the infection.9 This hypothesis is supported by a review of several studies since the start of the pandemic, which also demonstrated that a lack of microbial diversity is associated with more severe disease.10

An early study of patients admitted to Stanford health care from March 4 to March 24, 2020, also found 31.9% of the patients had GI symptoms on admission.11

Poor Microbiome Diversity Increases Risk of Illness

The links between poor gut microbiota and chronic diseases were made long before COVID-19. One of the underlying factors affecting the diversity of your gut microbiome is a Western diet that is characterized by a high intake of processed foods and sugar and a low intake of fruits and vegetables.12

This combination increases chronic inflammation and is associated with several highly prevalent chronic diseases, such as diabetes, cardiovascular disease and obesity. Kim began analyzing studies and making connections when he realized that countries with good medical infrastructures were among the hardest hit.

These countries ate a Western diet low in fiber, and he says that “a fiber-deficient diet is one of the main causes of altered gut microbiomes and such gut microbiome dysbiosis leads to chronic diseases.”13

This dietary pattern promotes an inflammatory response in the body and is associated with a sharp rise in “Western diseases.”14 One observational study of 1,000 healthy men and women found that eating processed foods leads to a significant reduction in gut microbiome diversity.15

Older age is also associated with reduced diversity of your gut microbiota. When compared to healthy adults, researchers hypothesize this difference may contribute to the development of chronic diseases.16 The changes in gut microbiome with age may be linked to changes in diet and lifestyle and medication use.

As more information was gathered about the progress of COVID-19, scientists identified groups of individuals with comorbidities that were at higher risk for severe disease. It appears one underlying factor between the groups of people who experience severe illness may be poor gut health.

Dr. Giancarlo Ceccarelli, an infectious disease specialist at the University of Rome, and colleagues, provided probiotics to 70 patients who tested positive for COVID-19.17 The results of their research were published in Frontiers in Medicine. The control group received hydroxychloroquine, antibiotics and the immunosuppressive drug tocilizumab, either alone or in combination.

The experimental group received the same therapy with the addition of an oral multistrain probiotic. Within 72 hours, diarrhea in those treated with the probiotic was in remission as compared to less than half of the control group.

Additionally, the intervention lowered the risk of developing respiratory failure eightfold and those in the control group had a higher risk of mortality. Ceccarelli commented on the results of the study:18

“Our preliminary results evidenced an improved survival rate and a lower risk of transfer to an intensive resuscitation for patients supplemented with the probiotic compared with those on standard treatment only. The gut bacteria have a long-reaching immune impact on the pulmonary immune system.

Our results stress the importance of the gut-lung axis in the control of the COVID-19 illness. Bacteriotherapy could represent an additional option for this severe disease.”

Probiotics Are a Potential Therapeutic Approach to COVID-19

Kim notes19 that dysbiosis in the gut microbiota may be the underlying factor that allows SARS-CoV-2 to access the otherwise well-protected cells of your intestinal lining. Ultimately, this allows the virus to leak into the body and affect internal organs, which may explain multiorgan dysfunction in those who are severely ill with the disease.

Kim proposes your gut health may be a critical factor that predicts symptom development. The reduced diversity in bacteria in those with severe COVID-19 includes bacterial families that produce butyrate. This is a short-chain fatty acid that is crucial to reinforcing the gut barrier function.

The resulting leaky gut from an altered microbiota may contribute to these gastrointestinal symptoms and allow the virus access to your internal organs.20 SARS-CoV-2 interacts with ACE2 enzymes found on the surface of many of these organs. This mediates the entry into the host cells and replication, which ultimately damages the tissue and promotes the severity of the illness.

In addition to protecting mucosal barrier function and inhibiting invasion of pathogenic bacteria, there are indications that your gut microbiota have a direct impact on bacteria in the lungs.21 Following sepsis, researchers have found an abundance of Bacteroides sp. in the lungs, which may indicate that the composition of your gut microbiome could be a predictive tool.

The first trial has started in Canada, but doctors in China have been using probiotics with other treatments for COVID since February 2020.22 The goal of the PROVID-19 randomized control trial23 is to evaluate whether probiotics could be a treatment option to reduce the duration and symptoms of patients who have tested positive for the virus and are not hospitalized.

A pilot study from the Chinese University of Hong Kong was accepted for publication in Gastroenterology.24 Researchers collected data from 150 patients with COVID-19 and 1,500 healthy individuals. The microbiome information was compared, after which they created a supplement of prebiotics and bifidobacterium strains.

The paper revealed only that “significantly more patients who received the formula achieved symptom resolution and a reduction in pro-inflammatory immune markers than those who had standard care.”

Probiotics Need Prebiotics to Flourish

The formulation the Chinese scientists developed increases the potential that beneficial bacteria will grow in your gut microbiome by also providing the nutrients they need to flourish. Prebiotics and probiotics are immunomodulatory.25 In other words, they both stimulate and suppress the immune system, which helps maintain homeostasis in the system.

After an evaluation of the current and past research demonstrating the powerful effect that your gut microbiome has on the immune system in combination with the current knowledge that this microbiome plays in the development of severe COVID-19, one scientist wrote:26

“In the event of a failure to produce a vaccine, it is believed that the best approach to fight COVID-19 infection is by improving the immune system using probiotics and prebiotics that have the potential to minimize the inflammation caused by COVID-19 infection.”

These are strategies you can begin to implement immediately without the need for a prescription from your doctor. Studies have confirmed that a high intake of sugar will increase the abundance of harmful bacteria in the gut, while at the same time simultaneously reduce the population of beneficial bacteria.27

Beneficial bacteria help to reinforce the gut barrier function and mitigate the effects of endotoxins released by harmful bacteria. Inulin is one type of water-soluble fiber found in asparagus, garlic, leeks and onions. The following whole foods help add prebiotic fiber to your diet and improve the health of your microbiome, thus improving your overall health:28,29


Breast milk
Burdock root

Chicory root
Fennel bulb

Green peas
Jerusalem artichokes

Konjac root


Savoy cabbage

Snow peas


Fermented Foods Are Flavorful and Often High in Fiber

Historically, the primary reason for fermenting was to preserve food. Over time, many cultures incorporated fermented foods into their daily diets, and some were credited with a selection of foods they shared with the world. For example, Japanese natto, Korean kimchi and German sauerkraut are popular in many areas outside their respective places of origin.30

The health benefits associated with fermented foods are many. In fact, the yogurt industry has used the growing interest in probiotics to advertise their products. While store-bought yogurt does have probiotic bacteria, it is also rich in sugar that feeds the harmful bacteria in your gut. This is just one reason why grocery store yogurt is typically not beneficial.

In the U.S., it’s becoming more popular to eat fermented foods at home. Yet, preparing them is largely a lost art. Probiotic-rich food, such as fermented vegetables, will boost the population of beneficial bacteria, which then reduce the potentially pathogenic colonies. Making your own yogurt at home is an easy way to start with fermented foods.

To make yogurt at home you only need a high-quality starter culture and raw, grass fed milk. You’ll find simple step-by-step instructions in “Benefits of Homemade Yogurt Versus Commercial.” You can also experiment with fermenting almost any vegetable. Cucumbers (pickles) and cabbage (sauerkraut) are among the most popular. Although it might seem intimidating at first, once you have the basic method down, it’s not difficult.

In the video below, I review how to do this. As I discuss in “Tips for Fermenting at Home,” there are several steps you can take to make the process a little easier. Begin with fresh, organic ingredients and be sure to wash them properly under cold running water. The idea is to remove bacteria, enzymes and other debris as this can affect the outcome.

Choose glass Mason jars with self-sealing lids. Most fermented vegetables will need to be covered with brine. I recommend using a vitamin K2-rich starter culture dissolved in celery juice. Allow the jars to sit in a relatively warm area for several days. The temperature should ideally be around 72 degrees Fahrenheit.

During the summer months, vegetables are typically finished in three to four days. In the winter, they may need up to seven days. The only way to tell when the fermentation process is complete is to open the jar and have a taste.

When you’re happy with the flavor and consistency, move the jars into the refrigerator. Refrigeration will slow fermentation and the vegetables can keep for many months. Remember not to eat out of the jar because you’ll contaminate the rest of the batch with the bacteria from your mouth. Make sure the vegetables are covered with brine before replacing the lid.

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