The viral link between COVID, gut health and immunity

Optimal gastrointestinal function can solidify gut health and immunity, potentially making one’s gut a stronger contender against viruses such as COVID-19

The Centers for Disease Control and Prevention (CDC) warns that having a weakened immune system may place a person at greater risk of developing a severe case of COVID-19 – even after being fully vaccinated. This agency adds that sometimes it is a medical condition that causes the immune system to weaken or 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. Among them are the circadian rhythm, metabolism, and responses to nutrition, but also immunity.

This review, which was published in Cell Research, goes on to say that the interaction between gut health and immunity is “complex, dynamic and context-dependent.” It begins early in life, with the microbiota becoming fairly stable by the age of three. However, if an infant faces certain environmental factors that change their microbiota before this stability can occur, it can render them more susceptible to infectious disease both short and long-term.

Additionally, the influence of the environment on gut microbiome doesn’t stop in infancy. Diet, the use of antibiotics, and a “westernized lifestyle” can all impact how well the gut can modulate disease later in life.

In the case of antibiotics, these medications can cause hyperactivity in the intestinal macrophages and expansion of proinflammatory cells, increasing one’s susceptibility to infection. A diet high in saturated fat reduces immunity as well by disturbing the homeostasis of the intestinal tract. Artificial sweeteners and emulsifiers can also have detrimental effects.

In February 2021, authors of research published in the journal Current Opinion in Immunology even referred to the gastrointestinal tract as “the largest immune organ” tasked with protecting the body against food-related toxins. But what does all of this have to do with COVID-19?

The connection between the gut, immunity and COVID

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

Typically, if a pathogen is recognized, the body activates the immune system, prompting the release of “natural killer cells” to destroy the infected cells. Whether they are effective for this purpose may be impacted, in part, by the number and diversity of bacteria in their gut.

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

Boosting gut health for strengthened immunity

If a reduction in bacteria increases the vulnerability of the system against diseases such as COVID-19, one way to reduce this susceptibility may be by increasing one’s number of good bacteria. Probiotics can assist with this.

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

Other studies add that probiotics can be especially helpful in fighting respiratory tract infections, a hallmark characteristic 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 2020 BMJ study concludes by saying that vitamins A, B6, B12, C, D, and E are also beneficial for supporting optimal immune function, as are the minerals zinc, copper, selenium, and iron. Together, these nutrients can help promote optimal gastrointestinal function, solidifying gut health and immunity and potentially making it a stronger contender against viruses such as COVID-19.