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Your Gut Is Proof That You Lived Through a Pandemic

Microscopy image of elongated bacteria in groups of two or three.
Credit: CDC / Unsplash.
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Throughout the course of the COVID-19 pandemic, everyone has had to make lifestyle changes and adapt to a new reality. Well, in fact, even our intestines have made changes. Dr. Ava Hosseini at the University of California (UC) San Diego Health and her team published a research study in Digestive Diseases and Sciences in which they highlighted the ways in which pandemic-related lifestyle changes are correlated with significant alterations in the microbial profile of the small intestine.

Exploring the pandemic’s influence on small bowel microbial makeup

The global COVID-19 pandemic has led to the death of over 6.5 million people worldwide and has required people to make significant lifestyle alterations, including changes in food consumption, exercise habits, alcohol and recreational drug use, hygiene practices and sanitization routines. While these changes have been observed in-depth from a public health perspective, many have had impacts on other aspects of human health that are relatively understudied. The gut microbiome plays an important role in human health and a variety of bodily functions, including metabolism, immune function and homeostasis. Disruptions to normal gut microbial profiles can lead to diseases such as inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), emphasizing the importance of a healthy and well-functioning gut in human health. It has been suggested that the prevention measures that were undertaken during COVID-19, as well as the changes in lifestyle practices, may be related to changes in the gut microbiome of people all across the world. Hosseini et al. conducted a study to understand the impact that lifestyle changes during the pandemic may have had on the composition of the duodenal microbiome.

Taxonomic changes in duodenal microbial profile of patients during the pandemic

For this study, the researchers collected data from 94 subjects between the ages of 18 and 85 who were undergoing a standard of care upper endoscopy without colon preparation. The subjects were divided into two groups based on their procedure date: pre-pandemic (February 2019 to March 2020) and intra-pandemic (April 2021 to September 2021). These subjects had already been enrolled in a study called “REIMAGINE”, in which scientists had collected duodenal luminal samples and blood samples from them, so Hosseini et al. used this data for their own analysis purposes.

The key findings of the paper were:

  • Significant taxonomic differences were found between the duodenal microbiome of patients from both groups.
  • The phylum Deinococcus-Thermus, which is known for being more resistant to changes in environmental conditions, was more prevalent in the duodenums of the intra-pandemic group, compared to the pre-pandemic group.
  • The relative abundance of several Gram-negative families was significantly lower in the intra-pandemic group versus the pre-pandemic group.
  • IL-18 was present in significantly lower circulating levels in the intra-pandemic group compared to the pre-pandemic group.
  • Lower levels of potential bacterial disruptors of the duodenal microbiome were found in the intra-pandemic group, such as Escherichia, Shigella and Rothia, compared to the pre-pandemic group.

Utilizing the small bowel microbiome to assess the pandemic’s overall effects on human health

Dr. Hosseini’s team was able to identify significant differences in the microbiome of patients who had samples collected before the pandemic versus after the pandemic, indicating the impact that pandemic-related lifestyle changes may have had on people’s small bowel microbiome. They found that forms of bacteria that are typically more resistant to changes in pH, radiation and heat, were more prevalent in the intra-pandemic group compared to the pre-pandemic group. Furthermore, they found that the concentration of IL-18, a potent pro-inflammatory cytokine, was significantly lower in patients from the intra-pandemic group compared to the pre-pandemic group. Previous studies have shown that elevated IL-18 levels have been associated with diseases such as rheumatoid arthritis or Type-1 diabetes. They suggested that the lower levels of IL-18 may be due to a lower relative abundance of disruptor taxa in the duodenum, but further research is needed to confirm this.

This study demonstrates the potential ways in which lifestyle changes during the pandemic are correlated with duodenum microbial changes, however, it is important to mention that there are limitations to this study. Firstly, all the participants in the study were scheduled for endoscopies for separate medical reasons, indicating the results of this study may not be representative of individuals with a healthy gut. Furthermore, this was a cross-sectional study, but it may be beneficial to conduct this study in a longitudinal manner as well to assess long-term changes in the duodenum microbial profile. Lastly, there are various confounding factors, such as diet, that were not accounted for in this study and could have impacted the microbiome.

Evaluating long-term changes in the small bowel microbiota

This study demonstrates the importance of studying the impact of various global events, such as the COVID-19 pandemic, on various aspects of human health that may not be studied otherwise, such as small bowel health. Through this approach, we can better understand the ways in which lifestyle changes can impact our health at different levels. Future research should build upon this study by developing longitudinal studies that can better assess the impact of the pandemic and other global events on the small bowel microbiome with regards to a larger time scale. Furthermore, a larger sample size could confirm or refute the trends and results that the researchers observed.

Reference: Hosseini A, Rashid M, Leite G, et al. Coronavirus disease 2019 (COVID-19) pandemic lifestyle changes may have influenced small bowel microbial composition and microbial resistance. Dig Dis Sci. 2023;68(10):3902-3912. doi:10.1007/s10620-023-08061-6