How a healthy microbiome reduces the severity of COVID infection and vice versa

A large number of microorganisms live in our gut, including bacteria, fungi and viruses
.
In general, we call this the microbiome
.
Although these microbes are small, they have important effects on
our health and well-being.
In fact, the microbiome is often referred to as the "second brain" because of its extensive relationship
with the body's organs and systems.

A particular role of gut microbes is to support immune function
.
They help control local and systemic inflammation, the process
by which the immune system protects us from harmful pathogens.

Therefore, it is not entirely surprising
that studies suggest that the composition of gut bacteria may influence the severity of COVID infection.
At the same time, evidence is beginning to suggest that COVID infection may affect the balance of gut bacteria, which may go some way towards explaining why some people experience persistent symptoms
after COVID infection.

The microbes in our gut provide the necessary signals
for the systemic immune response, including in the lungs.
The "healthy" gut microbiome includes a wide range of bacteria, although the bacteria in each person's body are not the same
.
Previous studies have shown that a healthy gut microbiome can improve the immune response
to respiratory infections by modulating immune cells and messages.

On the other hand, there is evidence that poor bacterial composition in the gut increases the susceptibility of the lungs to influenza infection and leads to reduced
clearance of bacteria from the lungs of mice.

With COVID, the composition of the gut microbiome also appears to influence the course
of the disease.
Studies have shown an association between microbiome characteristics and inflammatory marker levels in COVID patients, with patients with a poor combination of gut bacteria showing signs of
excessive inflammation.
This suggests that the microbiome influences the severity
of COVID infection through its influence on the immune response.

Imbalance of microflora

Just as the composition of our gut bacteria seems to affect how we respond to COVID, the opposite may also be true – COVID infection may affect the composition
of our gut bacteria.
Specifically, the coronavirus seems likely to upset the balance
between "good" and "bad" microbes in the human microbiome.

Studies have shown significant differences
in the gut microbiome between COVID patients and healthy people.
We have seen less bacterial diversity in the gut of COVID patients, so the range of species is smaller and the types of bacteria present are very different
.

Notably, scientists have observed a reduction in COVID patients in a population of a bacterium known as a commensal bacterium, which acts on the immune system and helps prevent the invasion
of pathogens.
This may increase our risk
of contracting other diseases after COVID.
At the same time, there appears to be an increase
in opportunistic pathogenic bacteria known to cause infection.

This "imbalance" is called dysbiosis, and these changes persist
in patients 30 days after infection.

Recent studies have shown that intestinal dysbiosis is associated
with the entry of gut bacteria into the bloodstream during COVID infection.
In mice, COVID caused changes in various parameters related to the permeability of the intestinal barrier, meaning that theoretically things could pass through the intestinal wall
more easily.

In the same study, in 20% of human COVID patients, certain bacteria in the gut had migrated into the bloodstream
.
People in this group are at higher risk of developing secondary infections in the
bloodstream.

Research now also suggests that dysbiosis after COVID may lead to long COVID, with intestinal dysbiosis more prevalent
in patients who develop symptoms of long COVID.
This makes sense, as dysbiosis appears to leave the body in a state of high and constant inflammation, which is associated
with chronic COVID symptoms.

Supports your immunity

As we continue to gain a more complete understanding of the gut microbiome and its role in inflammation, how can you help keep your immune system healthy and protect yourself from COVID and other infections?

Certain nutrients, including vitamins A, C, D, and E, as well as iron, zinc, and omega-3 fatty acids, all have a positive effect
on the immune response against viral infections.

The Mediterranean diet is rich in vitamins, minerals and dietary fiber, which has an anti-inflammatory effect
on the intestines.
Interestingly, a bacterium called Faecalibacterium prausnitzii is key
to immune regulation.
It is found very low in the Western diet but high
in the Mediterranean diet.

Ideally, you should avoid eating too many refined grains, sugar, and animal fats, which can all exacerbate inflammation
in the body.

Probiotics, a complementary blend of live bacteria, may also have benefits
.
Studies have shown that a mixture of Lactobacillus plantarum and Lactobacillus lactococcus can reduce the amount of virus detected in the nasal passages and lungs and shorten the duration
of symptoms in COVID patients.

The combination also significantly increased the production of COVID-specific antibodies, suggesting that probiotics work directly by interacting with the immune system, rather than just altering the composition
of the gut microbiome.

Finally, moderate exercise can also help support the immune system against the coronavirus
.

Lactobacillus plantarum induces innate cytokine responses that potentially provide a protective benefit against COVID‑19: A single‑arm, double‑blind, prospective trial combined with an in vitro cytokine response assay