Gut microbiome makeup could impact severity of COVID-19

Dear Doctor: I heard on the news that if your gut isn’t in good shape, you’ll probably get a worse case of COVID-19. Is that really true?

Dear Reader: A study published earlier this year put forth an intriguing theory about a link between the state of someone’s gut microbiome and the severity of their case of COVID-19.

Research has taught us that the vast colonies of microscopic creatures living in our guts are in constant communication with the brain and have an effect on everything from mood, emotions, sleep and weight to metabolism, blood-sugar control and a range of diseases. Considering this inextricable connection between the human gut microbiome and our health, looking into a potential relationship between the trillions of microbes in our intestinal tracts and COVID-19 seems like a logical step.

The study, published earlier this year in the journal Gut, builds upon previous inquiries into what role the gut may play in patients with COVID-19. Earlier studies have identified a measurable difference between the microbial composition of the guts of those patients and of people who were sick with a cold or the flu.

In this new study, researchers delved into the question in greater detail. They analyzed samples of blood and stool taken from 100 patients with COVID-19 whose disease was severe enough that they were admitted to the hospital and compared the results to samples drawn from 78 healthy control subjects. They discovered that species of certain bacteria that are known to play a role in the immune system were present in much lower numbers in the guts of the patients hospitalized with COVID-19. They also found larger populations of certain bacteria in the patients with COVID-19, including several that are associated with inflammation. The researchers saw this as evidence that an imbalance in certain bacterial colonies within someone’s gut might influence how severe their illness could or would become.

Eve Glazier, M.D. and Elizabeth Ko, M.D

They also found evidence of a potential link between these gut imbalances and the lingering symptoms known as long-haul COVID. For fellow science nerds, the bacterial overgrowth included a species known as Ruminococcus gnavus, which previous studies have shown to produce a simple sugar that causes inflammation. This bacterium has been linked to Crohn’s disease and diverticulitis.

It is important to note that, although results of this study suggest a connection between certain gut microbiome imbalances and a more severe case of COVID-19, they do not offer conclusive proof. There’s no way to know whether the specific array of microbes in these patients’ guts existed before they became infected with the novel coronavirus, or if they arose as a result of the infection and subsequent illness. Still, with the novel coronavirus and COVID-19 so new to the world, every additional bit of data is, at the very least, interesting. With any luck, it may prove important enough to help develop a cure. In that vein, some are holding out hope that this line of research into the gut microbiome of COVID-19 patients may someday lead to microbe-based therapies, each one tailored to a person’s specific gut microbiome.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)


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