Heather Richards, Director Of Nutrition at Sano School of Culinary Medicine, shares her views on staying healthy during the COVID-19 pandemic…

Food and The Immune System

This is absolutely a key time when we want our immune systems to be performing optimally. When we provide our bodies with the nutrients they need to perform optimally we give ourselves the best chance of staying strong and recovering if we are exposed to COVID-19.

Our bodies are miraculous and will spring into action through a complex number of mechanisms once exposed to the virus. It has been said that we are fighting ill health rather than a virus and that is an interesting concept. We are certainly seeing those with underlying health conditions being more impacted by the virus. 

A Healthy Immune Supporting Diet

Real food with variety

Nutrition can play a fundamental role in the health and functionality of the immune system. Sometimes this can be as simple as supplying adequate nutrients for normal cell function, right through to directly stimulating and upregulating specific immunological functions.

As well as considering specific foods and nutrients a diet that supports immunity is one that balances blood sugar levels. Simple sugars will not only feed opportunistic pathogens leading to dysbiosis and leaky gut but will also spike insulin levels. High insulin may upregulate the enzyme delta 5-desaturase that converts omega-6 fatty acids into inflammatory metabolites and hence aggravate the inflammatory cascade. 

So absolutely we can include more foods and nutrients in our diet specifically to support the immune system but adding these foods to a ‘less than optimal healthy diet’ is like building a house without the foundations. The first thing to do is to look at your diet and assess overall how it could become healthier.

During lockdown, many people have more time and are starting to get back to the basics of home cooking. This is great! The closer your diet is to a real food diet based on variety and colour the healthier it will be. When we talk about real food we mean using ingredients that have been provided by nature, they are not in packets. Easily remembered is;

“Real food doesn’t have ingredients, real food IS ingredients.” In other words, it doesn’t have labels or come in a packet.

“If it ran, swam, flew or grew, eat it, everything else should be left behind.” 

If you follow these two principles and include plenty of variety in your diet you will be well on your way to a good foundation. None of us are perfect and we are all on a health journey but any improvements you can make will be a benefit to your health and immune system. 

Coming on to specific nutrients that can support the immune system: what we are not saying is that any of these foods are going to stop you from being impacted by COVID-19 and its symptoms. However, the more optimally your immune system is functioning it is more likely you will experience milder symptoms and a faster recovery time as the immune system has the tools for defence. 

Probiotics & Prebiotics

Prebiotics: Jerusalem artichokes, Asparagus, Leeks, Onion, Garlic, Celeriac

Probiotics: Natural probiotic unsweetened yoghurt, Kefir, Sauerkraut, Kimchi, Miso

The gut microbiome has become almost fashionable to talk about these days and with good reason. A diverse microbiome is supportive of an appropriate immune response. Don’t be tempted to rush out and buy probiotic drinks or yoghurts that are often sugar laden. Instead, include in your diet prebiotic and probiotic foods. Prebiotics are the food supply of the probiotics so are vitally important too. 

Prebiotics are easy to include in the diet. Onions and garlic can be used as the flavour base for almost any meal. Fennel is currently in season and is delicious in a salad or pan fried. Incorporate asparagus into a salad or try a soft boiled egg with asparagus dippers instead of ‘bread soldiers’. To include probiotics add natural probiotic yoghurt to granola or muesli, pan fry salmon with miso or have sauerkraut as a condiment to almost any meal.

Zinc

Shellfish, Herring, Egg yolk, Beef, Liver, Lamb, Cheese, Pumpkin seeds, Sunflower seeds, Ginger, Almonds, Cashews

Zinc has traditionally been the forgotten nutrient when it comes to immunity, yet its role is vital. It is needed for the proper functioning of the immune system. Of particular interest is its microbial effect and the fact that it is found in the mucous secretions of the upper respiratory tract. People reach for vitamin C when they have colds and coughs but zinc is now a very common ingredient in many cold and flu formulae and for good reason. Zinc is used in hundreds of metabolic processes in the body and is not stored in the body so a regular intake through food sources is important. 

Zinc can be found in a variety of both animal and plant foods. Nuts and seeds can be sprinkled on salads, porridge or included in granola. Ginger is a great aromatic that can be used as the flavour base for many dishes and fresh ginger is readily available in supermarkets. The smell of grated or chopped ginger is amazing! Eggs, beef, liver and lamb are all a good source of zinc and of course top of the list is shellfish, prawns and oysters. This doesn’t have to be extravagant, you can purchase frozen prawns quite easily and add them to stir fries, salad, pad thai and curries.  

Vitamin C

Red Peppers, Spinach, Broccoli, Brussel Sprouts, Parsnips, Tomatoes, Goji berries, Kiwi Fruit, Citrus fruit, Blackcurrant, Rosehips, Strawberries

Vitamin C is an important nutrient for the overall health and functionality of the immune system. It affects immune function in several ways by supporting both the innate and adaptive immune system. In particular, Vitamin C regulates a specific immunological response called the oxidative burst. This is where leukocytes release a cloud of reactive oxygen species when faced with pathogens resulting in microbe death. 

When you think about Vitamin C in foods don’t just think citrus fruits, there are plenty of vegetable sources too; red peppers, spinach, broccoli, brussel sprouts and parsnips. Great additions to a roast, stir fries, salads and many other dishes. 

Vitamin D

Sunlight, Oily fish, Liver, Shellfish, Egg Yolk, Mushrooms

Vitamin D supports both the innate and adaptive immune system and the vitamin D receptor is expressed on many white blood cells. It supports the production of anti-inflammatory cytokines and a reduction in the production of inflammatory cytokines. Vitamin D is synthesised by the conversion of cholesterol, 7-dehydrocholesterol, in the skin to ultraviolet light.

However, when we spend a lot of time indoors or during the winter we can easily become deficient. In addition, it is harder for those with dark skin to make the conversion. Darker skin is a benefit when exposed to the sun in hot climates by providing protection from sun damage. However, living in the UK with dark skin is not beneficial to our vitamin D status! 

Thankfully there are some good food sources of vitamin D. Animal sources include oily fish, eggs, liver and shellfish.  An easy way to remember the oily fish is SMASH; Salmon, Mackerel, Anchovies, Sardines, Herring.

For a plant source look to mushrooms where the ergosterol in their cell walls is converted to vitamin D when exposed to sunlight. Try a breakfast of eggs and mushrooms, vegetable frittata including mushrooms and include oily fish in your diet.

Beta-Glucans 

Mushrooms and Oats

We have seen that mushrooms are a source of vitamin D but they contain another immune enhancing compound as well, beta-glucans. Beta-glucans are large complex sugar molecules, polysaccharides, found in mushrooms and oats. They increase NK cell numbers and stimulate the immune system to release cytokines and immunological response.

Vary your breakfasts with porridge, bircher muesli, eggs with mushrooms or frittata. A main meal could be mushroom risotto, mushroom stroganoff, mushrooms and sundried tomatoes on sourdough, stuffed mushrooms or even mushroom soup.