In a recent study published within the journal Nutrients, researchers review the impact of coronavirus disease 2019 (COVID-19) on the gut microbiota and microbiome-related immunity, in addition to the usage of dietary interventions, including pre- and probiotics in reducing the susceptibility to COVID-19.

Study: Functional Foods: A Promising Strategy for Restoring Gut Microbiota Diversity Impacted by SARS-CoV-2 Variants. Image Credit: ridersuperone / Shutterstock.com

Background

Because the onset of the COVID-19 pandemic, growing evidence indicates that nutrition and supplementation with essential minerals and vitamins can significantly reduce the severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

Vitamins C and D are known to enhance the immune response against viruses and reduce cellular stress and levels of reactive oxygen species. Likewise, minerals resembling zinc also contribute to the anti-viral response by enhancing the efficacy of anti-viral drugs and exerting their immune-protective effects.

Along with severe respiratory symptoms, fatigue, fever, and dyspnea, between 2-21% of COVID-19 patients also experience gastrointestinal (GI) symptoms resembling diarrhea, lack of appetite, nausea, and abdominal pain. Examinations of the gut microbiome of COVID-19 patients have revealed significant dysbiosis that increases their susceptibility to secondary infections within the respiratory and GI tracts.

The gut microbiome is crucial for processing and absorbing essential macro and micronutrients within the body, in addition to supporting immune function. Thus, understanding the impact of COVID-19 on the gut microbiome and developing dietary interventions to revive the microbiome balance may also help reduce the severity of SARS-CoV-2 infection and subsequent secondary infections.

COVID-19 and the gut microbiome

The presence of SARS-CoV-2 ribonucleic acid (RNA) in stool samples indicates that the virus can infect the GI tract and spread through the fecal-oral route. Furthermore, imaging techniques have revealed mesenteric thickening, hyperemia and bowel wall thickening, fluid-filled large intestine, and pneumatosis in patients with SARS-CoV-2 infections.

Diarrhea and nausea are essentially the most common GI symptoms experienced by COVID-19 patients, with gut dysbiosis believed to be a significant reason for these symptoms. Studies examining the gut microbiome of SARS-CoV-2 infected patients revealed a decrease within the abundance and variety of helpful bacteria resembling Faecalibacterium, Roseburia, and Eubacterium and subsequent increase in species resembling Clostridium hathewayi, Coprobacillus, and Clostridium ramosum that show positive associations with disease severity.

Dysbiosis, which involves the lack of helpful gut microbes, lack of overall microbial diversity, and increased abundance of pathogenic bacteria, is related to various other chronic diseases. Changes within the gut microbiome increase the danger of other comorbidities resembling Alzheimer’s disease, hypertension, asthma, and dementia, in addition to an altered immune system, the latter of which might increase a person’s risk of severe SARS-CoV-2 infection.

The age-related decrease in gut microbial diversity has also been implicated within the increased severity of SARS-CoV-2 infection in elderly patients. Obesity, which also has significant associations with gut microbiome dysbiosis, can also be correlated with severe COVID-19 outcomes.

Other risk aspects resembling diabetes and hyperglycemia, and cancers are also known to cause gut microbiome dysbiosis, which contributes to the increased susceptibility of diabetes and cancer patients to COVID-19.

Therapies and interventions

Antiemetic and antidiarrheal medications could be used to handle nausea and diarrhea related to COVID-19, together with regular rehydration and monitoring of potassium levels. Moreover, increasing helpful gut bacteria through the consumption of plant proteins, polyphenols, complex polysaccharides, and micronutrients may improve COVID-19 outcomes by increasing the production of short-chain fatty acids (SCFAs) needed for immune system regulation.

GI symptoms of COVID-19 can be alleviated by prebiotic intake, which helps restore the gut microbiome balance. The usage of prebiotics, which consist of fibers that increase gut fermentation and helpful gut bacterial growth, has been popular in various traditional medicine forms and addressing GI problems resembling diarrhea and constipation.

Probiotics help break down the varied fibers that constitute prebiotics, which subsequently results in the production of SCFAs that activate G-protein coupled receptors and influence the activities of assorted immune cells, resembling macrophages, T-cells, and dendritic cells. Certain probiotic bacteria also exhibit anti-viral properties against other coronaviruses.

Various natural compounds and herbal formulations are also being explored for his or her efficacy in reducing the severity of SARS-CoV-2 infection. These formulations often contain bioactive compounds resembling alkylamides, curcuminoids, and alkaloids which have anti-inflammatory and anti-viral properties.

Conclusions

The present study provides a comprehensive understanding of the impact of COVID-19 on the gut microbiome and the next increase in susceptibility to severe SARS-CoV-2 infection as a result of the detrimental effects of gut microbiome dysbiosis on immune function.

The researchers also discussed the varied therapeutic interventions resembling probiotics, prebiotics, herbal formulations, and functional foods that could be used to revive the balance of the gut microbiome, thereby improving immune system function and resilience against severe COVID-19 outcomes.