Ever since it became clear that certain groups of people were more at risk of the most dangerous COVID-19 symptoms, I have been interested to understand the role of the gut microbiome in the severity of COVID-19. This is because I noticed that most of the health conditions that place someone at a higher risk of severe COVID-19 were associated with a similar gut microbiome profile. As a result, I have been following the research that is emerging in this area, and it’s felt increasingly important to make this information accessible to everyone. I have waited for several key pieces of evidence to be published in the medical literature before writing this blog. This latest research is now indicating that taking care of your gut microbiome may be one important, empowering step you can take to protect yourself and those you love from the most severe symptoms of COVID-19.
JANUARY 2021 UPDATE: I wrote this blog in May 2020. All the research published on Covid and the Microbiome since then has confirmed the information I included. In June, I offered a series of three webinars explaining this research simply, yet in detail, with clear steps you can take to nurture a healthy gut microbiome through particular foods and lifestyle choices. The live series has concluded but recordings are available to purchase, until end of June 2021. These webinars are for anyone wanting to understand the research and take proactive steps to support their health and immune system – especially those who are concerned that their age, underlying health conditions or higher bodyweight places them at increased risk for the more severe COVID symptoms. You can read more about the series here.
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The microbiome is a vital part of our immune system
It’s widely understood that eating healthily supports our immune system. That makes sense because certain vitamins and other nutrients are essential to the healthy functioning of our immune system. Also, around 70% of our immune cells are located in our gut. But fewer people know that the population of microscopic organisms in our gut, commonly known as the microbiome, is an integral part of our immune system too.
Every individual’s microbiome is unique; like a finger print. The different bacterial species, and the proportions they are found in, are different for each person, and this has made studying the gut microbiome and its role in health and disease really challenging. However, researchers are increasingly focusing not just on the species that make up the gut microbiome, but on the overall balance of certain kinds of bacteria and the capacity of the microbiome to produce certain chemical products and how it operates as part of our immune system.
The microbiome protects us from infection in a number of ways. It even helps train our immune cells! But it also plays a very important role in regulating how our immune system functions, especially the aspect of our immune system that involves inflammation. There have been many studies in the past decade showing how the health of the gut microbiome can affect the health of our lungs, our immune responses to respiratory infection and the protective species in the microbiome of our lungs too.[1] What we eat, as well as our lifestyle, are major factors in determining the balance of microbial species that make up our gut microbiome, and therefore how it functions.
The only proven way to prevent coronavirus infection is by avoiding being exposed to the virus. But while it’s clear that most people suffer mild symptoms of COVID-19, the latest research is now indicating that taking care of your gut microbiome may be one empowering step you can take to protect yourself from the most severe symptoms. A few days ago, 125 of the UK's leading scientists signed a letter to the UK government by the All-Party Parliamentary Group on the Human Microbiome.[2] The letter calls on the government to take the emerging research on the role of the microbiome in preventing the worst symptoms of COVID-19 seriously. Now is the time, more than ever, for us all to take the health of our microbiome seriously – and for those of us who have the privilege of accessing good information and healthy foods, this is a tangible, positive step we can take in these challenging times. Healthy foods and healthy lifestyle choices have never been more important.
People most at risk of severe COVID-19 have a similar microbiome profile
Researchers around the world are now investigating a persuasive hypothesis that the gut microbiome is playing a vital role in protecting people from the worst of the COVID symptoms, but also that certain imbalances in the microbiome are making some people more susceptible to the severe symptoms. The groups of people most at risk from severe COVID include those with diabetes and Metabolic Syndrome (the medical term for a combination of diabetes, high blood pressure and obesity) as well as those who are older or obese (as defined medically).
All of these conditions tend to be associated with particular imbalances in the microbiome that contribute to inflammation – both locally in the gut and systemically in the body. For example, inflammation in adipose tissue (body fat) underlies what is medically termed as obesity. Although there are many elements that influence someone's bodyweight, including socioeconomic factors, it's becoming clearer how the microbiome often plays a key role – through influencing blood sugar regulation and nutrient absorption, as well as inflammation.
The microbiome protects us from inflammation
In recent years, research has shown that a healthy gut microbiome helps protect us from too much inflammation in the body. We’ve also discovered that too many of certain bacterial species in the gut microbiome contribute to inflammation – both in the gut but also elsewhere in the body. It’s the inflammatory aspect of our immune system, in particular, that is proving to be a very important in how severe the symptoms become when someone gets COVID-19.
A study released at the end of April, by researchers in China, has revealed that the severity of COVID-19 symptoms can be predicted by a set of proteins they found in people’s blood, including those associated with systemic inflammation.[3] Using machine learning with data from more than 300 people, the researchers correlated these proteins to the gut microbiome and identified which groups of gut bacteria were associated with these proteins and therefore make up a risk profile for COVID symptoms. The study size was relatively small (31 COVID-19 patients, and a group of 990 healthy individuals), and the paper is yet to be peer reviewed, but these preliminary findings are consistent with existing evidence of the role of the microbiome in inflammation, and are another indication that the health of the gut microbiome is likely to be a key factor in symptom severity.
The microbiome is thought to protect us from cytokine storms
One of the most dangerous symptoms of severe COVID has been reported to be a “cytokine storm”. This is an excessive production of certain chemical messengers in the body involved in inflammation known as cytokines – leading to a kind of hyperinflammation that can be deadly. Inflammatory cytokines are regulated by the gut microbiome and are now understood to be important factors in the severity of symptoms and death of COVID-19 patients.
According to several reports, patients with Type II Diabetes and Metabolic Syndrome might have up to ten-times greater risk of dying when they contract COVID.[4] This finding is thought to be due to these patients having a state of inflammation that predisposes them to an enhanced release of cytokines. Certain people are at greater risk of metabolic syndrome, especially older people and people within certain ethnic groups. This may partly explain why frontline keyworkers in Black, Asian and Minority Ethnic (BAME) communities are tragically disproportionately affected by the most severe COVID symptoms. Microbiome imbalances may be a further example of the effects of structural racism on BAME health, and this is a much needed focus of microbiome research.
The microbiome protects us from age-related inflammation
In recent years, research has shown that the microbiome can become depleted as we get older. You can read more about the changes in the microbiome with ageing here. This may be a natural decline in microbiome function, or due to the kinds of changes in diet and lifestyle, as well as medication, that often accompanies older age.
The species in the gut microbiome can become less diverse as we age, and in particular, the populations of bacterial species in the microbiome that protect against inflammation can become reduced, while those that contribute to inflammation become increased. This imbalance is linked to many age-related health conditions – including obesity, heart disease, osteoarthritis, liver disease and more. Recent studies have shown how eating a healthy diet can reduce inflammation in older people[5] and this confirms other studies that show how the foods we eat can nurture a microbiome that supports our health.
How can we support the health of our gut microbiome?
A diverse microbiome is a healthy microbiome, with lots of different microbes that can perform a range of functions and protect us from infections. We also need a good abundance of species that protect us from inflammation, and low numbers of those that promote inflammation. There are many routes to imbalances in the microbiome, and the health conditions that can accompany those imbalances; these include medical interventions, such as long term (although often necessary) use of non-steroidal anti-inflammatory pain killers or antibiotics. The composition of your gut microbiome is affected by many things, including diet, lifestyle, health history, genetics, where you live and even your birth.
However, diet can really shape our microbiome, and this knowledge can be empowering if we are able to make sure we have a varied diet that supports microbiome diversity, and if we can eat the foods that feed bacteria that protect against inflammation, and avoid a diet that feeds those that contribute to inflammation.
In general terms, understanding what makes a good diet that encourages a healthy microbiome is very simple. It can be summarised by comparing the Standard American Diet (SAD) with the Mediterannean Diet. The SAD diet is high in sugars, processed carbohydrates and fats. It’s low in the kinds of foods that nourish a healthy microbiome, and it’s high in the foods that encourage the species that contribute to inflammation. The SAD diet is also low in variety – people eat the same, limited number of vegetables and grains each week – and this means their microbiome becomes less diverse too. Over time, this diet promotes an inflammatory microbiome that impacts not only the health of the gut lining, but contributes to inflammation all over the body.
In contrast, the Mediterranean Diet ensures that the bacterial species responsible for anti-inflammatory capacity of your microbiome are well nourished, and the microbiome has a good diversity of species. This diet includes plenty of colours (polyphenols that feed beneficial bacteria), a wide variety of grains, vegetables and fruits, and includes a good variety of soluble fibres (known as prebiotics) as well as healthy oils.
I was excited to discover that gut microbiome interventions are just starting to be trialled in the treatment of COVID-19. Researchers in the United States are planning to investigate the role of prebiotics in preventing hospitalisation of COVID patients in a clinical trial[6] while several others are trialling various probiotics. A comprehensive article published in a Dutch medical journal a few days ago has also outlined the potential for using nutritional strategies, including probiotics and prebiotics, to support recovery from COVID-19, but also as a way to protect frontline care workers.[7]
What steps can you take?
The unique mix of microbes that makes up our individual gut microbiome is also influenced by our genetics, our birth and childhood, health history (including medication), as well as our diet and lifestyle. The immune system is also complex and highly responsive to the world around us, so many factors affect its function, and our immune system is heavily influenced by our lifestyle and the world around us.[8] This means there are many variables that effect how different people respond to the new coronavirus infection – including genetics and other factors (some of which we don’t yet understand or even know about).
The steps you take will be unique to you, your health and current situation. It’s important to remember COVID-19 is still a very new disease and even with the amazing research focus that is engaged around the world, there is still very limited information on all the risk factors. But where there are ways to support our health and immunity that are within our power – including nutrition, exercise, sleep and stress management – that is empowering and useful knowledge. While none of us had immunity to this novel coronavirus, making sure we’re feeding the beneficial bacteria in our gut microbiome seems to be one way we can reduce our risk of getting seriously ill.
As a microbiome analyst, assessing the anti-inflammatory capacity of a client’s microbiome, and making sure the beneficial bacteria are well nourished, is always a priority. For many of my clients, this has been an investment in healthy aging, for others with health conditions where inflammation is a major factor (such as Multiple Sclerosis) the result has been improvement in symptoms. These are one to one sessions, using microbiome stool test results, so my recommendations for certain foods, as well as prebiotics and probiotics are tailored to each individual’s unique bacterial profile and health history.
However, there is some information on healthy eating for microbiome health that can apply to people more generally, and it feels important to share this widely during these coronavirus times. This is why I am offering a webinar series on how to take care of the beneficial bacteria in your gut to protect against inflammation, and more details about what we know so far about the role of the microbiome in protecting us from the worst symptoms of COVID-19.
Please find out more about this 3-part webinar series here, and consider forwarding this information to anyone you feel could benefit.
REFERENCES [1] For example: Hufnagel et al (2017) The respiratory tract microbiome and lung inflammation: a two-way street Mucosal Immunol. 10(2): 299–306 [2] https://twitter.com/AppgMicrobiome/status/1260969491569262593?s=20 [3] Gou et al (25 April 2020). “Gut Microbiome May Underlie the Predisposition of Healthy Individuals to COVID-19.” MedRxiv, , 2020.04.22.20076091. [4] Bornstein et al (02 April 2020) Endocrine and metabolic link to coronavirus infection Nature Reviews Endocrinology 16: 297–298 [5] Ghosh et al (17 February 2020) Mediterranean diet intervention alters the gut microbiome in older people reducing frailty and improving health status: the NU-AGE 1-year dietary intervention across five European countries. Gut. [6] https://www.clinicaltrials.gov/ct2/show/NCT04342689
[7] Dhar et al (13 May 2020) Gut microbiota and Covid-19- possible link and implications Virus Res. 198018 [8] Brodin et al (2015) Variation in the human immune system is largely driven by non-heritable influences Cell 160(0): 37–47
Thanks Phil for taking the time to comment, and it’s a good point. You’re right, I can only comment from my area of expertise and I’m not an epidemiologist or statistician, but there are a number of theories as to why the situation in Italy was so devasting, including how the outbreak (ie infection rate) was initially handled. In time we may know more, if the data exists. In order to address your point, we would need comparative data on the percentage of all those infected who went on to have serious symptoms, and we’d need to know how many people in Italy’s hotspots do actually eat a Mediterranean diet. An existing body of research shows the microbiome plays a key…
Much as the Mediterranean diet may be good for the gut. Italy has had one of the worst epidemics of COVID-19 despite their Mediterranean diet - that would seem to blow a big hole in the writer's theory. Perhaps if the only speciality you have is Microbiome the whole world looks like the gut?