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Your Gut Health May Play a Role in COVID-19 Severity

Woman with stomach pain wearing a mask with a nurse.

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Key Takeaways

  • Chronic conditions linked to severe COVID-19 are also associated with an altered gut microbiome.
  • Some studies suggest that a diverse gut microbiome may help people avoid gastrointestinal issues during a COVID-19 infection.
  • There is not yet enough data to pinpoint how gut health and COVID-19 outcomes are connected.

During COVID-19 infection it can be important to listen to your gut. We've all heard of the commonly reported high fevers and loss of sense of smell due to COVID-19. But many patients also experience issues stemming from the gastrointestinal tract, such as diarrhea, nausea, and vomiting.

Emerging evidence suggests that an altered or unbalanced gut microbiome may allow the virus to enter the GI tract and can be an indicator of COVID-19 severity.

A review article published in mBio this month by Heenam Stanley Kim, PhD, a professor at Korea University’s Laboratory for Human-Microbial Interactions, looks at the status of research on COVID-19 and the gut microbiome. Kim writes that when the gut is in dysbiosis—meaning the microbiome is out of balance—a person’s digestive tract and internal organs may be more susceptible to severe COVID-19 symptoms.

The gastrointestinal organs are protected by what is known as the gut barrier—the mucosal layer, epithelial cell layer, and cellular immune system which work together to protect the gut. If this barrier is compromised, pathogens like viruses may be able to access intestinal cells and cause inflammation and other systemic damage.

Chronic conditions such as high blood pressure, diabetes, and obesity are among the many factors which contribute to COVID-19 infection and severity. Kim writes that these conditions and older age are also often associated with an altered gut microbiome and disrupted gut barrier integrity.

And because “gut symptoms have consistently been associated with more severe illness in COVID-19 patients, it is possible that dysfunction of the gut as a whole influences COVID-19 severity,” Kim writes.

What This Means For You

Scientists haven’t yet drawn a direct connection between the gut microbiome and COVID-19. But having a healthy gut can help your overall health. To support a healthy gut, you can eat a diet high in fiber, cut down on refined sugars, limit antibiotic use, and eat fermented foods.

Breeching the Gut Barrier

Intestines in the gastrointestinal tract contain an angiotensin-converting enzyme 2, or ACE2. This compound acts as a binding site for SARS-CoV-2, the virus that causes COVID-19, mediating the virus’ entry into host cells. If the virus interacts with ACE2 in the gut, Kim hypothesizes that this may lead to inflammation or organ damage.

“Based on the proposed hypothesis, when GI is not healthy, SARS-CoV-2 can get access to the surface of the epithelium or even penetrate it if gut barrier integrity is seriously compromised,” Kim tells Verywell via email. “Then the immune system can overreact to the virus further damaging the gut barrier integrity.”

When this happens, he says the virus can get into the bloodstream and travel to other organs, infecting them and causing serious illness.

The presence of SARS-CoV-2 may not always lead to GI symptoms. In a study conducted in Singapore, half of the participants had a detectable level of coronavirus in fecal tests. However, only about half of that group experienced GI symptoms like vomiting and diarrhea. 

The connection between gut health and disease outcomes for conditions like irritable bowel syndrome has been studied by microbiome researchers for years. While researchers now know that a diverse microbial community and strong gut barrier are important factors for a healthy GI tract, the precise microbial species which make the gut healthy remain unknown.  

“The challenge is that the evidence that is there is not really sufficient to implicate the microbiome yet, so while it’s ok to hypothesize and test these approaches, I don’t think we're at the point where we can draw the conclusion that it’s one of the factors driving pathogenesis in COVID-19,” Purna Kashyap, MBBS, co-director of the Mayo Clinic Center for Individualized Medicine Microbiome Program, tells Verywell.

Kim says that future studies will need to investigate or confirm important interactions between COVID-19 and the gut. One is the link between severe COVID-19 illness and gut symptoms like diarrhea or leaky gut. Additionally, Kim says scientists should continue to investigate the associations between leaky gut, systemic viral load, and multi-organ dysfunction.

Examining Waste for Clues

To understand the make-up of the gut’s microbial community, scientists can examine a person’s waste. The composition of bacteria, fungi, and phages in fecal matter provides clues to the relative health of a person’s gut. If this microbial community is not very diverse, or there are too few beneficial bacteria, it may indicate that a person’s gut is out of balance.

Examining fecal matter can also show whether the virus passed through the gastrointestinal tract of a COVID-19 infected person. Viral particles that end up in the gut may be from an upper respiratory tract infection.  

While this can be helpful for learning whether the virus traveled to the gut, Kashyap says it does not necessarily show how the virus interacted with GI organs.

“We don’t know if this is viable virus, which means we don’t know if they’re just passing through the gut or if they’re having an effect on the gut,” Kashyap says.

On a larger scale, scientists have begun testing for viral shedding in wastewater systems to identify viral outbreaks in communities. If there is evidence of viral particles in sewage, it could be an indication to public health officials that people who use the waste system are infected with COVID-19.  

What’s Left To Learn

Scientists still have much left to learn about how individuals can influence the health of their gut microbiome.

Still, research shows that certain dietary changes can support gut health, including:

  • Eating food high in fiber
  • Consuming fermented foods that contain live cultures of beneficial bacteria
  • Cutting down on processed sugars and carbohydrates

A diet high in fiber can support a healthy gut by providing necessary nutrients to the beneficial microbial species and by strengthening the gut barrier.

Kim recommends people consume between 25 and 30 grams of dietary fiber per day over a long period to create the right conditions for a healthy gut.

“If a person rarely consumes dietary fiber or recently had an antibiotic therapy, there is no doubt that this person has gut microbiota dysbiosis,” Kim says. “If a person has a chronic disease such as diabetes or obesity, there is a high chance of having gut microbiota dysbiosis, but it depends on the severity of the chronic disease.”

Strengthening the gut microbiome before COVID-19 infection, he says, can help protect the gastrointestinal tract against potential effects of the virus as it travels down from the respiratory tract.

Kashyap says he expects to see more research on the linkages between COVID-19 and the gut microbiome in the coming months and years after the immediate threat of the pandemic has subsided.

“I think we will be in a better position to study patients once the pandemic is under control because right now, you have to give priority to the clinical care of patients,” Kashyap says.

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