The COVID-19 pandemic has shifted the focus of research for scientists worldwide, probably making science nimbler once the crisis has passed. The coronavirus has also had implications for patient care that we are only just beginning to understand. While patients infected with SARS-CoV-2 typically present with a respiratory illness, certain individuals also report gastrointestinal symptoms that have been linked to changes in the gut microbiome.
Although COVID-19 has captured the world’s attention in 2020, relevant breakthroughs in gut microbiome science have also been made, which elucidate on the role of diet in managing diseases and conditions, not necessarily connected to the gut, through the gut microbiome. In addition, scientists have also re-classified the Lactobacillus genus, provided an updated consensus on synbiotics, and gained a better understanding of how microorganisms in fermented foods can be transferred to the human gut and impact health outcomes.
Here are some of the breakthroughs in gut microbiome science seen in 2020.
How might the gut microbiome fare in the fight against COVID-19?
The respiratory symptoms of COVID-19, the ability of the virus to bind its receptor expressed along the gastrointestinal tract, and an altered gut microbiota composition in some patients means the gastrointestinal tract can be considered a potential target in the fight against COVID-19.
Although a study previously looked at the role of prebiotics and probiotics in reducing the incidence and duration of viral respiratory infections and improving the efficacy of the seasonal influenza vaccination, it is too early to recommend them as a means of tackling coronavirus. Fecal microbiota transplants also constitute another approach for targeting the gut microbiome, but can potentially transmit COVID-19 and can transfer extended-spectrum beta-lactamase-producing gut bacteria in immunocompromised elderly patients.
Diet, gut microbiome and immune homeostasis in gastrointestinal health and beyond
Diet is considered one of the biggest determinants of gut microbiome composition and, therefore, of an immune system in good shape, with gut microbiome heterogeneity becoming a relevant player in individual responses to diet, lifestyle and medication. COVID-19 is an external insult that can activate an immune response, which is accompanied by a higher demand for nutrients that support the functioning of the immune system. While we await an effective vaccine against COVID-19, consuming sufficient amounts of essential nutrients in the context of a plant-based diet to support the immune system seems to be an approach worth considering to help the host better defend itself against the virus if infected.
In 2020, scientists have improved their understanding of the therapeutic effects of diet mediated by the gut microbiome in both gastrointestinal conditions and systemic diseases. Different sources of evidence in humans have shown that peppermint oil, specific probiotics, psyllium supplementation and the low-FODMAP diet can aid in improving IBS symptoms. On the other hand, the inflammatory potential of diet has been linked to the risk of Crohn’s disease, a phenotype about which the gut microbiome might have a lot to say. Understanding how diet impacts the gastrointestinal ecosystem has also shed light on the importance of taking care of diet for tackling hypertension, the mechanisms underlying the keto diet’s health benefits, and identifying microbial signatures in the liver, adipose tissue and blood linked to type 2 diabetes.
Rather than focusing only on changes in gut microbiota composition, scientists have also become interested in how diet-derived or microbial-mediated metabolites play a crucial role in celiac disease, help identify patients at risk of inflammatory bowel disease that will develop into ulcerative colitis, and aid in the development of new antidiabetic drugs.
Altogether, the findings highlight that current guidelines for managing systemic conditions that apparently have no link with the gut should pay attention to diet as a central element of treatment, with the gut microbiome an important part of the puzzle.
Beyond diet, the herbicide glyphosate has drawn scientists’ attention, due to its impact on human health linked to changes in the gut microbiome.
Gastrointestinal health and the gut microbiome: time to focus on the small intestine
Many oral-associated bacteria have been identified in the stomach and small intestine, but their association with the intestinal mucosa may not merely be a result of luminal contamination. Although the small intestine is a harsh environment for microorganisms to thrive and methodological challenges exist when studying the small intestinal microbiota, it has become a relevant area in the context of functional gastrointestinal disorders and enteropathies such as celiac disease.
It is also interesting to note that bacteria in the small intestine could also be involved in boosting inflammation that makes it harder for children to get the calories and nutrients they need.
New re-classification of Lactobacillus genus and updated consensus on synbiotics
Diet, probiotics, prebiotics and postbiotics are current evidence-based strategies for modulating the gut microbiome. A close look at bacterial whole-genome sequences of Lactobacillus species has enabled scientists to reclassify this genus into 25 genera, which include 23 novel genera. One of the main implications of this discovery is that a new explanation of the changes in genus names should be provided to academic journals and searches in the scientific literature should also consider this new classification.
When it comes to synbiotics, a panel of experts under the auspices of the International Scientific Association for Probiotics and Prebiotics (ISAPP) has updated the definition and scope of the word ‘synbiotic’. One of the novelties of the definition is that the microorganisms that must be targeted by the prebiotic can include either members of the individual gut microbiota (complementary synbiotics) or microorganisms co-administered in the synbiotic (synergistic synbiotics).
It should also be acknowledged that not all diseases in which probiotics, prebiotics and synbiotics have been studied exhibit the same degree of gut microbiota alteration. In addition, human microbiota-associated mice studies, considered a cornerstone model in microbiome research, are not free of limitations, which highlights the need for improving experimental rigor when testing for causality in the field.
Major advances in the mechanisms supporting the health benefits linked to fermented food consumption
The microbiomes of fermented foods are extremely diverse and their potential health-promoting attributes are superior when compared to nonfermented equivalents. In addition, consuming fermented foods rich in lactic acid bacteria has been shown to enrich the human gut with these potentially probiotic microorganisms, in a similar way to probiotics.
Although the health benefits of fermented foods have been known for centuries, the underlying mechanisms have only recently been elucidated. Yogurt is one example of that. Observational data have shown that health benefits associated with yogurt consumption may be explained as a result of improving gut barrier function. Indeed, in the light of current science, only some fermented milks such as yogurt and some kefirs can be considered a source of probiotics.
When it comes to the application of fermented foods for mental health, a meta-analysis of 22 randomized controlled studies has revealed that it is still too early to recommend fermented foods, probiotics or prebiotics for improving cognition.
Despite COVID-19 limitations, the Gut Microbiota for Health World Summit 2020 was held in Madrid, attracting a large turnout among online attendees.
GMFH will continue to cover the important progress made in 2021 in updating the latest cutting-edge science on gut microbiome, nutrition and immunity for better overall health and well-being. We will also bring you more information on the 10th edition of the GMFH World Summit, which we hope will be held in Washington in November 2021.
We wish you a very happy 2021. Don’t forget to stay tuned over the coming year!