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expert reaction to observational study looking at the gut microbiome and long COVID

An observational study published in Gut looks at gut microbiota dynamics in patients with post-acute COVID-19 syndrome.


Prof Amitava Banerjee, Professor of Clinical Data Science, Univerwsity College London, said:

“The distribution and type of microbes in the body (the so-called “microbiome”), particularly in the gut, has been invoked as a potential explanation for onset of various chronic diseases from colon cancer and heart disease to rheumatoid arthritis. Until now this has not been studied in the context of Long Covid. In this novel study of 106 people with Long Covid in Hong Kong, three-quarters had persistent symptoms at 6 months. In this research, the authors collected stool samples 1- and 6-months after discharge from hospital with COVID-19 to look for specific patterns of gut microbiome which were associated with Long Covid. Interestingly, the authors found that alterations in the gut microbiome were clearly associated with Long Covid. As the authors acknowledge, this is a small sample size and these impressive results need to be confirmed in larger population-based studies. Future research also needs to include non-hospitalised Long Covid patients. There are important implications for future research regarding the mechanisms of disease underlying Long Covid which have tended to ignore the gastrointestinal system, and also for trials of potential therapies and diagnostic approaches.”


Dr David Strain, Chair of BMA Board of Science and Clinical senior lecturer and honorary consultant. University of Exeter Medical School, said:

“It is hugely interesting, and actually fits nicely with the manuscript today in Nature Communications (Immunoglobulin signature predicts risk of postacute COVID-19 syndrome  by Cervia et al. 

“The manuscript suggests that there are differences in the microbiome, that is the bacteria that live in our gut that we are dependent on for health, between people who develop long COVID, or Post Acute COVID Syndrome, and those who make a complete recovery from their COVID-19. These differences are apparent at diagnosis although are exaggerated after 6 months.

“This finding is consistent with several existing hypotheses that Long Covid may be associated with a small quantity of residual virus in the immuno-privileged tissue (i.e the regions of the body such as the gut, that the protection of our antibodies doesn’t reach). It also accounts for the observations that we have seen non-genetically related households (e.g. husband and wife) affected by long COVID more than would be anticipated. 

“It is important to clarify that there are some substantial potential confounders in this study. Notably that this is in a Hong Kong population that have a significantly different diet to the UK population and are have been demonstrated to have substantial differences In their dominant gut species. Further these are observational data. We know that in the setting of fatigue, brain fog and the other non-specific symptoms of long COVID, diet changes with an (often inappropriate) shift towards higher energy food in the hope that it will help tackle the debilitating symptoms. These dietary changes also come with a change in the dominant components of the microbiome, therefore it is possible that this simply represents the reactive changes to post acute Covid syndrome. 

“If confirmed in a European/UK population it does offer a very promising area of study. The modification of the gut microbiome is feasible with dietary modification with supplements, indeed there have been attempts to treat other conditions (with varying degrees of success) through these methods.”



Gut microbiota dynamics in a prospective cohort of patients with post-acute COVID-19 syndrome’ by Qin Liu et al. was published in Gut at 23:30 UK time on Tuesday 25th January.

DOI: 10.1136/gutjnl-2021-325989



Declared interests

Prof Amitava Banerjee: “I am the PI of the STIMULATE-ICP trial (funded by NIHR) which is evaluating investigations, drugs and rehabilitation approaches in people with Long Covid.”

None others received.

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