The microbiome: health, longevity, and Covid-19 risk

Does the microbiome help explain the Covid-19 symptom disparity?

This has been the year of the germ. At no point in our lifetime have we been as preoccupied with microbial life as we’ve been in the last too-many months, plenty of us playing germ detective as we suspiciously follow people’s hands and coughs.

As we enter our second year of dealing with Covid-19 one mystery remains largely unsolved: We have a few clues, but still don’t understand the disparities in outcome between countries and people, and why some people experience a life threatening, even deadly disease, while others experience few or no symptoms. 

This year of turmoil has taught us some respect microbial life, however. Tiny organisms can disrupt the entire world, wreaking havoc upon us. But they are also a key actor in our survival, resilience, and in our fight against diseases and infections – our life depends on the microbes in our own body, where they recycle, produce and defend us, and we also utilize them in the industrial production of many of the chemicals and pharmaceuticals we use, from vitamins, to antibiotics and vaccines.

Does our inner microbial world also play a role in the Covid-19 symptom-disparity enigma?

Covid-19 and the microbiome

Our digestive system is highly involved in immune and inflammatory responses, and researchers have been studying the link between Covid-19 severity and the microbiome. This connection between the gut and respiratory infections is nothing new: the severity of other viral infections, such as the flu and pneumonia, is linked with certain microbial communities residing within people.

Does the composition of gut bacteria, the microbiome, affect Covid-19 severity? Gut microbes modulate and train the immune system, so a connection is plausible. Many of the risk factors for Covid-19 are also known to be associated with an altered microbiome: Advanced age, obesity and chronic illness are linked with a less diverse and less healthy gut community. So although one might suspect that an altered microbiome typical of these risk factors might be also influencing Covid-19 severity, disentangling cause and effect is challenging. A few small studies suggest that an imbalance in gut bacteria, as well as absence of beneficial bacteria, is typical in Covid-19 patients, and correlates with disease severity.

Could attention to the microbiome and improvements in gut populations affect Covid outcomes? A few trials are testing the effects of probiotics in Covid-19 patients.

Gut microbes, diet, disease and longevity

What’s gaining further proof over the years is the connection between diet and the microbiome. A large recent study, involving more than 1000 people, published in Nature Medicine found a connection between bacterial populations in the gut and the risk of conditions such as diabetes, heart disease and obesity. The researchers found a clear and consistent link between beneficial versus harmful bacterial populations and diets, and the quality of a diet was predictive of the microbiome composition. People who eat a healthy diet, rich in plants, low in highly processed foods, have a specific panel of beneficial microbes, as well as low levels of blood markers that indicate inflammation, risk of cardiovascular disease, and glucose intolerance. 

Another recent study of 9000 people between the ages of 18 to 101 looked at how the microbiome may affect longevity. The study, published in Nature Metabolism, found that the type of microbes in one’s gut changes with age, developing with time, and becoming more unique and personal as years go by. In people in their late eighties, low uniqueness of bacteria, and high amounts of the Bacteroides type of bacteria, are associated with poor health and lower likelihood of survival.

So do these microbiome changes just reflect good health leading to longevity or actually contribute to it? The authors suggest that metabolites of a healthy microbiome, such as indoles, are known to reduce inflammation, and since chronic inflammation is thought to be a major driver of chronic diseases and aging, good bacteria may actually promote good health.

Supporting a healthy microbiome

Each of us is a universe: We host trillions of microbes, with microbial cells outnumbering ours nine to one. All this metabolically active life within us affects our health. Our genes are responsible for just two percent of our microbiome profile according to a study in the journal Nature;  the rest is not predetermined. Dietary and lifestyle habits, medications and the environment matter much more.

The key dietary components to keep in mind when thinking about the health of your microbiome are whole plant foods (fruits, vegetables, grains, legumes, nuts), lots of fiber (whole plant foods take care of that), and reduction of refined and highly processed foods.

Good bacteria thrive on the same foods that we hosts do.

Another thing to keep in mind for when the pandemic finally eases, is that our widespread use of disinfectants and cleaning products, as well as social distancing and all the other measures we’ve put in place to mitigate the pandemic’s spread, also stand to change our environment and our microbial population.

Covid-19 prevention, much like the disease itself, may be affecting our microbiome.

Dr. Ayala

“The key dietary components to keep in mind when thinking about the health of your microbiome are whole plant foods (fruits, vegetables, grains, legumes, nuts), lots of fiber (whole-plant foods take care of that), and reduction of refined and highly processed foods”