Nutritional self-defence against COVID-19

12 October 2020

As long-time readers will know, at this time of year I’m normally in California, attending the International Plant-Based Nutrition Healthcare Conference.

For rather obvious reasons, the conference was switched to an online format this year. I missed the warm, friendly atmosphere of this unique event, and the opportunity to catch up with previous attendees whom I’ve got to know over the six years that I’ve been attending this conference… but I can’t say I missed the loooooong flight, or the jetlag!

As usual, the presenter line-up was stellar. One of the most fascinating presentations – and one of the most relevant, given the ongoing presence of SARS-CoV-2 in our lives – was delivered by Dr William Li, founder of the Angiogenesis Foundation.

Dr Li described the mechanisms by which SARS-CoV-2 causes damage to those who develop COVID-19 (which, it must be remembered, is a small minority of those who actually come in contact with the virus) and how we can use nutrition to protect ourselves against becoming infected in the first place, and falling ill if we do.

Does that sound interesting? Let’s jump in!

SIgA

Secretory immunoglobulin A (SIgA) is a protective protein produced in our mucous membranes. SIgA is a key component of our adaptive immune system. Its role is to trap and neutralise pathogens, so that they’re unable to cause infection. Think of it as a first responder to any invasion attempt.

However, as Dr Li explained, the efficacy of SIgA is dose-dependent – the more SIgA present in our mucous membranes, the greater the chance that it will be able to ‘mop up’ all of the incoming viruses before they’re able to do us harm.

Mushrooms contain beta-d-glucan, a polysaccharide (complex sugar) that has been shown to raise SIgA production. Dr Li shared a study in which 24 healthy volunteers were randomly assigned to either continue their normal diet, or to add 100 g of blanched white button mushrooms to their regular daily diet for 1 week, and then to return to their regular diet.

Remarkably, by the end of week 1 of the experiment, average SIgA secretion in the saliva of the mushroom-eaters had increased by 53%. Even more remarkably, it continue rising after they stopped adding mushrooms to their diet, ending up 56% higher than their baseline SIgA secretion by the end of week 2.

After two weeks sans mushrooms, SIgA secretion in the mushroom eaters returned to baseline levels. SIgA production did not change in the control group.

The researchers pointed out that previous studies have found that:

“A decrease in sIgA [salivary IgA] secretion has been associated with the incidence of upper respiratory illness symptom.”

Dietary intake of Agaricus bisporus white button mushroom accelerates salivary immunoglobulin A secretion in healthy volunteers

While this was a small study and its results need to be confirmed in a larger trial, adding mushrooms to one’s diet on a regular basis is inexpensive, and offers multiple nutritional benefits with no risks.

Dr Li noted that chanterelle mushrooms have twice the content of beta-d-glucan as white button mushrooms, so if you are able to obtain chanterelles in your area, go for it!

(Side note: another powerful intervention to raise sIgA production is exercise. Among elderly people who were given pedometers to track their daily activity, those who who accumulated approximately 7000 steps per day had the highest salivary sIgA levels, while those who accumulated less than 4166 had the lowest.)

γδ T cells

Gamma delta T cells (γδ T cells) are the next line of defence after SIgA – not quite a first responder, but an early responder which will join the battle if SIgA fails to repel the enemy’s first attack.

Cranberry polyphenols have been shown to trigger a rapid expansion in the number of γδ T cells and to significantly decrease cold and flu symptoms.

In a randomised, double-blind, placebo-controlled trial, volunteers who drank a beverage containing cranberry polyphenols each day for 10 weeks, had γδ T cells that proliferated nearly 4 times faster than volunteers who drank a placebo beverage.

The cranberry-drinkers’ white blood cells also produced more interferon gamma, a powerful antiviral protein.

And the cranberry drinkers also reported fewer symptoms of upper respiratory tract infection over the course of the study.

The same researchers had previously shown that a powdered fruit and vegetable juice concentrate and concord grape juice also increased the number of circulating γδ T cells, while green tea powder boosted γδ T cell proliferation by 28% and increased the cells’ secretion of interferon gamma by 26%, while reducing cold and flu symptoms by 32%.

NK cells

Natural killer (NK) cells are another class of early responders in the immune system’s army. They destroy virus-infected cells in order to prevent the infection from spreading.

As Dr Li explained, anthocyanins – the red, blue, purple and black pigments that give berries, pomegranates, dark grapes, red onions and kidney beans their vibrant colours – activate T cells, enhancing their virus-busting activity.

Dr Li cited a study in which daily consumption of 250 g of blueberries for 6 weeks substantially increased NK cell counts, curbed the drop in NK cells that normally occurs after intense exercise, and also boosted production of an anti-inflammatory cytokine called interleukin 10 (IL-10), a chemical that limits ‘friendly fire’ damage inflicted by the immune system when it is combating infection.

Inhibiting SARS-CoV-2 entry

In order to enter our cells and cause infection, SARS-CoV-2 (the virus associated with COVID-19) uses a spike protein to bind to the ACE2 receptors on the membranes of cells in our respiratory and gastrointestinal tracts, and in our blood vessels, kidneys and liver.

Fucoidans – complex carbohydrates from the sea vegetable kelp (also known as kombu) – have been found to bind to SARS-CoV-2’s spike protein, thereby inhibiting it from binding to ACE2 and entering our cells. And these compounds from seaweed are actually more potent than remdesivir, the costly antiviral drug used to treat people hospitalised with COVID-19!

Gut microbiota

You knew this one was coming, didn’t you? It’s common knowledge now that 70-80% of our body’s immune system resides in the gut, and that the teeming colonies of bacteria, archaea, fungi, viruses and protists that comprise the gut microbiota play an integral role in shaping our immune responses.

Dr Li highlighted a fascinating study in which researchers used previously-published data on blood biomarkers of COVID-19 patients to construct a blood proteomic risk score (PRS), which predicts the progression to severe COVID-19 among infected patients.

They then took serum proteomic profiles (patterns of blood protein profiles) from over 2000 uninfected people, and compared them to the COVID-19 PRS to identify those who might be at risk of severe disease if they contracted the virus.

Next they identified core features of participants’ gut microbiota which were associated with the blood proteomic biomarkers of COVID-19, and also analysed the metabolic activity of participants’ gut bacteria in order to identify potential biological mechanisms linking gut microbiota to susceptibility to COVID-19.

And what did they find?

Lactobacillus bacteria, which thrive when we drink green tea and eat a high-fibre diet, were associated with higher levels of infection-fighting interferon gamma and also interleukin 6, which is crucial in readying B cells – one of the two main subtypes of cells in our acquired immune system – for battle.

Blautia bacteria, which digest complex carbohydrates such as those found in fruits, vegetables, whole grains and legumes, were associated with higher levels of interleukin 10, which you’ll remember helps to damp down the inflammatory response to infection and thereby limit damage to our healthy cells.

Pulling it all together

A wholefood plant-based diet, which emphasises brightly-coloured fruits and legumes, mushrooms, seaweed and green tea, complemented by regular exercise, will equip your immune system with the weapons it needs to defend you against infection with SARS-CoV-2 and help to reduce your chances of serious illness if you do become infected.

If you are overweight or have a chronic disease that puts you at increased risk of serious illness from viral infection, NOW is the time to take action on it! Obesity, type 2 diabetes, hypertension and coronary artery disease are preventable and largely reversible with a wholefood plant-based diet and Lifestyle Medicine. Apply for a Roadmap to Optimal Health Consultation today; online, phone and in-person appointments are available.