Many COVID Symptom Tracker participants have been asking our scientists whether there are certain foods that they should be eating to help combat COVID-19 or fend off coronavirus infection.

Let’s get things straight and start by saying there are no specific foods that will prevent or treat COVID-19. 

The only proven way to prevent coronavirus infection is by avoiding being exposed to the virus. There’s also a lot we still don’t know about why some people are more likely to become severely ill with COVID-19 while others have only mild symptoms or none at all - something we’re hoping to find out through our research. 

To reduce your chances of catching coronavirus, follow government guidelines including regularly washing your hands and avoiding physical contact with others. This is particularly important for protecting at-risk groups including people with existing health conditions, the elderly and pregnant women. As you may have seen in our latest analysis, lockdown is working, so let's continue to work to flatten the curve.

While it might feel like there is a lot of uncertainty right now, there are still many positive things you can do to support your health and that of the people around you at this difficult time. One of them is making sure you’re supporting your immune system by eating a plant-rich diet that supports the trillions of microbes living within your gut, collectively known as the microbiome.
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(As a side note, we should always be careful to talk about supporting healthy, normal immune response rather than trying to ‘boost the immune system’. An unnecessarily overactive immune response can be as risky as an under-active one, leading to autoimmune diseases and unwanted inflammation. In the most serious cases, a wildly overactive immune response can set off what’s known as a cytokine storm, which can cause respiratory failure and death.)

What’s the connection between the immune system and the microbiome?

The immune system is complex and highly responsive to the world around us, so it’s not surprising that there are many things that affect its function. But we do know that most of these factors are not hard-coded in our genes, but are influenced by lifestyle, previous illnesses and the world around us.

The interaction between your microbiome and your immune system is not yet well understood. However, recent research has shown that microbes that live in your gut (microbiome) play an essential role in the body’s immune response to infection and in maintaining your overall health.

For example, we know that your gut bugs enhance anti-inflammatory responses and activate vitamin A from your food - a vital molecule that helps to control your immune system.

How to keep your gut microbiome (and your immune system) healthy

A diverse microbiome is a healthy microbiome, with lots of different microbes that can perform a range of functions and fend off infections. Your microbiome diversity naturally drops with age, so you need to work harder to keep a good mix of microbes as you get older

You can increase the diversity of your microbiome by eating lots of plant-based foods, which are high in fibre, and limiting ultra-processed and junk food. If you’re unsure of where to start, take a look at ZOE’s Top Ten Tips to get more plants in your diet. 

Recent research has shown that following a Mediterranean diet can improve your gut diversity and reduce inflammation, helping to maintain overall health.

This involves eating plenty of fruit, vegetables, nuts, seeds and whole grains; healthy fats like high-quality extra virgin olive oil; and lean meat or fish for those who wish. 

Load up on brightly coloured fruit and vegetables that are high in beta-carotene (the precursor of vitamin A) and vitamin C, such as spinach, carrots, sweet potatoes, red peppers, mango, papaya and apricots.

You might be worrying about how to get hold of fresh fruit and vegetables if you are stuck in self-isolation or quarantine, but remember that frozen fruit, berries and veg are just as good for you as their fresh counterparts and will last much longer than two weeks. Canned fruit, beans and pulses are also a useful long-lasting option.

Tim Spector, of King's College London recommends:

"You can also boost your microbiome by adding in artisan cheeses and natural yoghurt, which both contain live microbes. Try a regular shot of other natural probiotics like kefir (fermented milk) or kombucha (fermented tea)."

Maybe take a tip from the Koreans and tuck into some kimchi - a tasty mix of fermented vegetables like cabbage with chili and garlic. Here’s a recipe if you have some time on your hands to make your own and can get hold of the ingredients.

And although it’s tempting to hit the sweet stuff or the booze right now, you’ll do more favours for your microbiome by keeping alcohol, sweets and sugary drinks as treats, and avoiding artificial sweeteners and similar additives.

Read more:

• Variation in the human immune system is largely driven by non-heritable influences – Cell
• Interactions between the microbiota and the immune system – Science 
• Gut microbiome regulates the intestinal immune system - ScienceDaily
• 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 Microbiota

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