Although COVID-19 primarily attacks the respiratory system, the virus can affect almost every organ and tissues in the human body, including immune and digestive systems.
An approach to reduce the impact of COVID-19 on health and well-being includes looking after what you eat and your lifestyle.
The GMFH editing team had time to speak with INRAE Research Director Joël Doré on what have we learned from the last months on the role of nutrition and a healthy gut microbiome for reducing the risk of contracting COVID-19.
Several studies published in 2020 have linked unhealthy eating habits, chronic inflammation and the risk of contracting COVID-19. Why it is important paying attention to the close connection between what we eat, the gut microbiota and immunity in COVID-19 times?
Not only do chronic conditions, promoted by unhealthy eating, clearly increase the risk of contracting or developing a more severe form of Covid-19, but also it is well established that these come with low-grade inflammation. It is also clear that anti-inflammatory drugs may beneficially contribute to avoid severe forms involving the so-called inflammatory storm* typical of severe Covid-19. It is hence reasonable to speculate that improving gut microbiota profile by personalized nutrition and supplementation known to improve immunity can be one of the prophylactic ways by which the impact of this disease can be minimized.
Which groups of people are at a higher risk of severe cases of COVID-19 and how might taking care of gut microbiota with diet and lifestyle help them?
The risk of developing a severe form of Covid-19 is higher in older people, and in people of all ages with pre-existing medical conditions that share as a common feature an inflammatory context (heart or lung conditions, weakened immune systems, severe obesity, diabetes, asthma).
In this context, any means of promoting immune homeostasis could possibly be protective. For example, probiotics with the ability to protect from diarrhea or to reduce gut permeability could help.
What do and don’t we know about the impact of COVID-19 on the gut microbiota, susceptibility to inflammation and long-term health outcomes?
- There is increased intestinal inflammation in COVID-19 occasionally with acute diarrhea.
- Pilot studies suggest gut dysbiosis in SARS Cov2 infection with loss of bacterial richness and diversity, loss of butyrate producing beneficial bacteria and proliferation of pro-inflammatory bacteria. The infection would also alter gut barrier permeability, promoting passage of bacteria and microbial metabolites that otherwise should remain in the gut.
- Dysbiosis and disease severity were associated, and it was even observed that dysbiosis persisted after viral clearance** and resolution of respiratory symptoms.
The current concept is that the dialogue between the microbiota and the immune system is central to mechanisms of infection and expression of the disease in Covid-19. Alteration of natural defenses (immunosuppression, immunosenescence, low grade inflammation) will induce dysbiosis. In turn, altered natural defenses and altered microbiota may mutually sustain one-another, favoring uncontrolled inflammation. Persistence of dysbiosis following resolution of major symptoms could explain long and difficult recovery from associated symptoms (altered gut transit, joint pain, headaches, anxiety, allergic symptoms, loss of taste and smell).
Gastrointestinal disorders have been reported to be frequent in COVID-19. How does gut microbiota change across the lifespan and what is the ability of COVID-19 to affect the gut microbiota? Why is it important to take care of the gut microbiota in frail older adults?
The scientific literature on microbiota changes in the old age documents a loss of richness which is associated with diminished reactivity of natural defenses. With loss of microbiota richness, the ecosystem will be less robust to assaults such as infection. It will neither fight nor recover as well. If in addition natural defenses are also diminished, infectious bacteria or viruses will induce more severe consequences. In such contexts it is a good preventive attitude to take care of the microbiota with a rather high diversity of fibers, in other words a large variety of raw or cooked vegetables and fruits that may confer protective benefits on the gut barrier and thereby the microbiota. Ideally, one would want to include probiotics from food sources or in the form of supplements and micronutrients documented for their ability to protect from gut hyper-permeability, inflammation, oxidative stress and possibly visceral sensitivity. For instance, the combination of yogurt and fruits contributes to intake of beneficial probiotic bacteria and key nutrients associated with increased gut microbiota diversity, including prebiotic fibers, vitamins and minerals.
What can we expect from future research on the role of gut microbiota in helping humans fight COVID-19?
We are truly microbial, we are ecosystems and we live in symbiosis with our microbiota that provides numerous beneficial functions. Preserving the richness and functionality of our gut microbiota will certainly help and possibly reduce the risk of contracting or developing a severe form of Covid. We should see this as a preventive and protective measure that should in addition have many more benefits as it will reduce the risk of numerous chronic conditions.
* Proteins that play a role in signalling to other cells how to regulate their activity and function (fight off disease for example).
** Meaning the absence of the virus in the organism.