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The Gut Microbiome And The Link To Other Body Systems

Updated: Nov 1

Patients with a severe covid-19 infection requiring hospitalization, tend to have hyperinflammation with highly elevated cytokines including IL-6, IL-17, and TNF-alpha, as well as decreased lymphocyte counts.

Since the start of the pandemic researchers have been trying to identify whether there is a specific link between the gut microbiota and severity of Covid-19 infection. Some of this research has uncovered that specific species in the Bacteroides and Streptococcus genera appear to exacerbate pro-inflammatory factors, whereas Ruminococcus, Blautia and Lactobacillus genera appear to down regulate pro-inflammatory factors, together this indicates that gut dysbiosis may play a role in the severity of Covid-19. Further studies have showed that an abundance of Coprobacillus, Clostridium ramosum and Clostridium hathewayi were positively correlated with dysbiosis and the severity of Covid-19, whereas butyrate producing Faecalibacterium prausnitzii was inversely correlated with the disease severity in hospitalised patients.

It is important as Nutritional Therapists to consider the various risk factors including old age, chronic diseases, gut infection, use of antibiotics and stress in the development of gut dysbiosis and subsequent pathogenesis of disease, also emerging is the further understanding of the bi-directional axis that exists between the gut and many organs and tissues in the body, all of these factors are major players in the resistance resilience and recovery of Covid-19 and long covid.

A correlation has been found between a reduction in Butyrate production in the gut and cardiovascular disease in patients with Covid-19. A reduction in butyrate leads to a higher rate of intestinal permeability or "leaky gut" and inflammasome activation, furthermore gut dysbiosis may be a pathogenic factor in hypertension through bacterial metabolites, sympathetic nervous system stimulation and endotoxaemia.

Lipopolysaccharides and microbes are able to cross gut barrier to enter the liver. After processing in the liver, they enter circulation and cause further activation of immune cells and cytokines.

A dysbiotic gut promotes inflammatory profiles in lung conditions such as asthma, cystic fibrosis, lung cancer and chronic obstructive pulmonary disease. Likewise, viral lung infections can disturb the gut microbiota that contribute further to dybiosis. This bidirectional interaction may exist in Covid-19. A destructive feedback loop can form where pro‐inflammatory cytokines may transfer through the systemic circulation, further accelerating dysbiosis in both the gut and the lungs.

NOTE: There is much more to come on the Gut-Lung axis as this is an emerging area of research so please watch this space.

We are only really beginning to understand the implications of dysbiosis in multiple areas of the body and how these interact with each other. Gut health cannot be improved simply by taking probiotic supplements since the "optimum" gut microbiome has yet to be identified. I also have an inkling that everyones gut microbiome is as unique as their fingerprint, which adds further dimensions for interventions. Start simple by looking to food first and consider supplementation only if there is a clinical need. Check out these further studies if you are interested in doing more research (shared to me by a colleague on LinkedIn)

"Supportive therapy during COVID-19" / "The proposed mechanism of short-chain fatty acids (#butyrate ) to prevent cytokine storm and multi-organ failure" / "Supplementation with butyrate could help to limit the cytokine storm"

“it is prudent to propose changes in dietary recommendations in favor of a high fiber diet or supplementation with Short Chain Fatty Acids (SCFAs) or probiotics to prevent or alleviate the neuropsychiatric ramifications of COVID-19”



Chen J, Hall S, Vitetta L. Altered gut microbial metabolites could mediate the effects of risk factors in Covid-19. Reviews in Medical Virology. 2021 Sep;31(5):1-13

Yeoh, Y.K., et al., 2021. Gut microbiota composition reflects disease severity and dysfunctional immune responses in patients with COVID-19. Gut, [online] 70(4), pp.698–706.

Liu, Q., et al., 2022. Gut microbiota dynamics in a prospective cohort of patients with post-acute COVID-19 syndrome. Gut, [online] 71(3), pp.544–552.
Rajput, S., Paliwal, D., Naithani, M., Kothari, A., Meena, K. and Rana, S., 2021. COVID-19 and Gut Microbiota: A Potential Connection. Indian Journal of Clinical Biochemistry, [online] 36(3), p.266.

Zhang, D., Li, S., Wang, N., Tan, H.Y., Zhang, Z. and Feng, Y., 2020. The Cross-Talk Between Gut Microbiota and Lungs in Common Lung Diseases. Frontiers in Microbiology, 11.

Dumas, A., Bernard, L., Poquet, Y., Lugo-Villarino, G. and Neyrolles, O., 2018. The role of the lung microbiota and the gut–lung axis in respiratory infectious diseases. Cellular Microbiology, 20(12).

Thomas, C., Auwerx, J. and Schoonjans, K., 2008. Bile Acids and the Membrane Bile Acid Receptor TGR5—Connecting Nutrition and Metabolism., [online] 18(2), pp.167–174.


Rachel Jessey holds a Masters Degree in Personalised Nutrition and Diploma in Nutritional Therapy. She has undertaken extra training in function medicine and has a keen interest in the immune system and autoimmune conditions. As well as conducting ongoing research Rachel runs a busy eConsult clinic in the UK and has been in clinical practice for over 12 years.

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