What does the latest research say on the connection between gut health and immunity? We interview the experts, plus give tips on how people can improve their gut health in an effort to lower their risk of COVID-19.

Brierley Horton, M.S., R.D.
October 27, 2020
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You might already know that your gut microbiome—aka the bacteria that live in your gastrointestinal tract—can have an impact on your immune system.

And if not, let us fill you in: research suggests that good-for-you bacteria compete with illness-causing pathogens to help keep you healthy. But this requires high numbers of those beneficial microorganisms, otherwise so-called "dysbiosis" (an imbalance of the system) occurs and that may help foster an environment that breeds illness.

So, with that sort of research in mind and being in the midst of a global pandemic, experts decided to explore a potential connection between our microbiome and the coronavirus.

"Since emerging evidence is showing more and more how the gut microbiome can play an important role in keeping us healthy, we wanted to support research that examines the role of the microbiome related to COVID-19 incidence and outcomes, which is an urgent public health crisis currently impacting the world in so many dimensions," says Miguel Freitas, Ph.D., vice president of scientific affairs at Danone North America.

You see, not only are there hundreds of viruses that cause respiratory infections, but research also suggests a legitimate connection between the gut and lung microbiota systems—and that connection is one that could spur or temper COVID-19.

So, Freitas and others wanted to know: Can a healthy gut help protect you against COVID-19, or even simply minimize your symptoms?

We connected with him, and also with Martin J. Blaser, M.D., director of the Center for Advanced Biotechnology and Medicine and a professor of medicine and microbiology at Rutgers University— two researchers working on this exact hypothesis—and asked them about the state of the science.

Here's what they had to say:

Q: How might a healthy gut potentially protect you against COVID-19?

Martin Blaser: As we all know, some people have mild COVID-19 infections, whereas it is very severe in others. What are possible explanations for the diversity in outcomes? One idea is that the nature of the inflammatory response that a person mounts against the virus is an important determinant of what will be their outcome. In other studies, it has been shown that the status of the microbiome influences characteristics related to inflammation. Changing the characteristics of the microbiome, ideally with a probiotic or prebiotic, could be one solution. The jury is still out, but this is an active area of research that we and others are exploring.

Q: What can we all do right now to improve our gut health and potentially improve our immunity against COVID-19?

Miguel Freitas: Make sure you're eating right. Both your digestive and immune systems are impacted by your diet—support them by consuming a varied diet, including fruits, vegetables, whole grains and certain fermented foods that contain probiotics. Your digestive system is home to billions of bacteria representing your gut microbiome, but it also houses 70% of your immune system. This is why certain foods can both benefit your gut health and immune system. I personally encourage people to consume fermented products like yogurt and kefir to support gut health and the immune system.

Also, getting enough sleep, exercising regularly and managing your stress can positively impact your health. (Try these dietitian-approved tips for supporting your immune system.)

Q: Probiotics versus prebiotics: does one make more of a difference?

Miguel Freitas: Probiotics and prebiotics are different realities. Probiotics are good bacteria or live microorganisms which, when consumed alive and in sufficient quantities, may have a beneficial effect on health. Certain probiotics have been shown to help support the immune system, while others help support the digestive system.

Prebiotics aren't bacteria. They're dietary fibers that are food for the good bacteria in your gut, typically found in onions, bananas and certain cereals. Consuming prebiotics can help increase the number of good gut bacteria, positively impact your microbiome and ultimately help support gut health.

Q: What is the status of the current research with COVID-19 and gut health?

Martin Blaser: One limitation of the research is that most scientists are studying the characteristics of the microbiome in people after they have been infected. But to understand its role in modifying disease, it is important to study the microbiome before the infection. It's nearly impossible to obtain specimens before an infection, unless a population of healthy people is assembled and studied; this is called a cohort study. We have enrolled a cohort of more than 800 healthy people in New Jersey, and some of them became infected with the COVID-19 virus. Thus, we have samples before, during and after their infection. This will allow us to perform comparisons with people who never became infected, those who had mild infections and those who became more severely ill.

The situation surrounding COVID-19 continues to change; it's possible that information or data has changed since publication. While EatingWell is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations by using the CDCWHO and their local public health department as resources.