The viral link between COVID, gut health and immunity

Optimal gastrointestinal function can boost gut health and immunity, potentially making the gut a more potent competitor against viruses such as COVID-19

The Centers for Disease Control and Prevention (CDC) warns that a weakened immune system can put a person at an increased risk of developing a severe case of COVID-19 – even after being fully vaccinated. The agency adds that sometimes it’s a medical condition that weakens the immune system or the long-term use of certain medications. But others suggest a link between gut health and immunity – that a potential link between immune system function and the development of severe COVID lies in the gut.

Gut health and immunity

A 2020 review of immunity and disease explains that the gut microbiome actively affects many bodily functions. These include circadian rhythm, metabolism and responses to nutrition, but also immunity.

This review, published in Cellular research, goes on to say that the interplay between gut health and immunity is “complex, dynamic and context dependent.” It starts early in life, with the microbiota becoming quite stable around the age of three. However, if an infant is faced with certain environmental factors that change their microbiota before this stability can occur, it can make them more susceptible to infectious diseases in the short and long term.

In addition, the influence of the environment on the gut microbiome does not end in early childhood. Diet, antibiotic use, and a “westernized lifestyle” can all impact the gut’s ability to modulate disease later in life.

In the case of antibiotics, these drugs can cause overactivity of intestinal macrophages and expansion of pro-inflammatory cells, thereby increasing susceptibility to infections. A diet high in saturated fat also lowers immunity by disrupting homeostasis of the intestinal tract. Artificial sweeteners and emulsifiers can also have harmful effects.

In February 2021, the authors of the research published in the journal Current opinion in immunology even called the gastrointestinal tract the “biggest immune organ” responsible for protecting the body from food-borne toxins. But what does all of this have to do with COVID-19?

The link between gut, immunity and COVID

A 2020 summary published in BMJ Nutrition, Prevention & Health indicates that the gastrointestinal tract acts as a barrier, preventing environmental pathogens from entering the human body. The mucous layers of this tract serve as a layer of defense, others including stomach acids and organisms present in the intestines.

Typically, if a pathogen is recognized, the body activates the immune system, causing the release of “natural killer cells” to destroy infected cells. Their effectiveness can be influenced, in part, by the number and diversity of bacteria present in their gut.

As the author of this summary points out, some studies have shown that COVID-19 patients have low numbers of certain gut bacteria, namely lactobacilli and bifidobacteria. Since these bacteria generally strengthen the barrier against environmental pathogens, when they are deficient, the system becomes more vulnerable to pathogenic organisms.

Boost gut health for enhanced immunity

If a reduction in bacteria increases the vulnerability of the system to diseases such as COVID-19, one way to reduce this sensitivity may be to increase the number of good bacteria. Probiotics can help with this.

Research has shown that probiotics have many positive effects. They work by promoting the production of macrophage chemotactic protein 1, for example, which sends signals to immune cells to activate the mucous immune system. Probiotics also activate T cells which release IL-10, a potent anti-inflammatory drug that helps limit the amount of damage a pathogen can cause.

Other studies add that probiotics may be particularly helpful in fighting respiratory tract infections, a hallmark feature of COVID-19. For example, a 2016 systematic review of 23 trials involving 6,269 children found that subjects taking probiotic supplements were sick for fewer days.

The BMJ 2020 study concludes by saying that vitamins A, B6, B12, C, D, and E are also beneficial in supporting optimal immune function, as are the minerals zinc, copper, selenium, and iron. Together, these nutrients can help promote optimal gastrointestinal function, solidify gut health and immunity, and potentially make it a stronger competitor against viruses such as COVID-19.

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