A doctor explains how our immune systems work and what we can do to help them function normally.

In the current climate, health is on everyone’s minds and we are all thinking “How can I avoid catching the coronavirus?”

We are washing our hands incessantly, standing two metres away from each other and running a mile when someone coughs.

But many of my patients are asking me whether there is a way to boost their immune systems to help protect them.

The short answer is no. No amount of kale or flaxseed will stop you from catching this contagious and serious viral infection. Hand washing, social distancing and self-isolation remain the only current ways we have to actively prevent it.

Our immune systems do not have an on and off switch that a supplement will flip.

Instead, the immune system relies on a complex integration of various cells, organs, proteins and tissues which work together to recognise and neutralise pathogens.

Furthermore, the immune system is not designed to be “boosted”, and if it were able to work in overdrive it could actually result in us becoming more unwell by damaging our healthy cells and tissue as well, which is what can happen in “autoimmune” conditions.

However, there are numerous nutrients, vitamins and minerals that are required to support the normal functioning of your immune system.

Most of these nutrients, except for vitamin D, can be sourced easily from a well-rounded, healthy diet. While we are aware that malnutrition can impair immune function, providing you have an adequate intake, any product suggesting its pill will “boost” your immunity is likely to be misleading.

It may laud the evidence to support that supplement as one of the factors in the functioning of the immune system, but it is unlikely, in isolation, to be able to do very much for you.

Vitamin D

Vitamin D is often associated with the healthy development of bones, joints and muscles. However, we are learning more about this humble vitamin, and now understand that it is associated with far more than just our skeleton.

It has been found to adapt our immune responses, and that a deficiency in it can be a trigger in autoimmune conditions and susceptibility to infections.

Vitamin D is primarily made from a reaction of the sun on our skin. During the winter months, when the sun does not often shine through the clouds and is weaker when it does, this can be difficult to achieve.

Some foods, including oily fish, egg yolk, meat and offal, contain vitamin D in small amounts. However, for most of the population, a maintenance dose of vitamin D in the form of a supplement is required over the winter months, recommended by the NHS at a dose of 10mcg Vitamin D3 daily.

Zinc

Zinc is known to be an important “micronutrient” for the immune system, and a deficiency of it can result in an impaired immune response.

There is even evidence to suggest that by taking a zinc supplement within 24 hours of a cold commencing, it can reduce the severity and duration of the illness.

Zinc can be found in plenty of foods, including seafood, meat, beans and pulses.

B vitamins

Several members of the B vitamin complex, namely vitamin B6, B12 and B9, have been implicated in the immune response.

Vitamin B12 is naturally found in animal products, including fish, meat, poultry, eggs, milk and milk products, so where vegans are not adequately supplementing their diets they can develop a deficiency.

Vitamin B6 is needed to absorb vitamin B12 and to make red blood cells and cells of the immune system. It can be found in foods including beef liver, chickpeas, tuna, salmon, rice, cereals and onions.

Most people only ever hear about folic acid (vitamin B9) in pregnancy as women are advised to take it daily in the first three months. Its role in pregnancy is to ensure that your baby does not develop neural tube defects such as spina bifida.

Folic acid is naturally present in a wide variety of foods, including dark green leafy vegetables, fruits, nuts, beans, seafood, eggs and meat.

These B vitamins have been found to have a role in the immune system, and a deficiency in them can alter the response of the immune system. This is by inhibiting the body’s ability to make antibodies, white blood cells and other immune factors it needs to fight off infection.

Vitamin C

Vitamin C has an essential role in normal immune function. It is found most richly in fruit and vegetables and aids the formation of collagen, wound healing and is an antioxidant.

This means that it scavenges free “radicals”, which are charged particles that can damage cells, tissues and genetic material, which can affect your immunity.

Most of us can achieve the recommended daily amount of vitamin C by simply eating a large orange, though smokers may need a slightly higher intake as, according to the National Institute of Health, smoking can deplete the body’s vitamin C.

Gut microbiome

The microbiota is the community of trillions of bacteria, fungi and other microorganisms that colonise our bodies, and the microbiome is the collection of them in a particular environment, in this case, the gut.

Not only does the gastrointestinal tract harbour a vast microbiome, but it also contains a large pool of immune cells.

The gut microbiome has been found to communicate with these immune cells, thus controlling how your immune system works and responds to infection.

As such, keeping these bacteria healthy with prebiotics and probiotics may also keep your immune system functioning normally.

Again, supplements are not required for this as there are plenty of foods that contain these properties. Pre-biotics are essentially the non-digestible fibre that the bacteria ‘feed’ off, and probiotics are the beneficial bacteria themselves, and can be found in yoghurts, artisan cheeses and many fermented goods including kimchi, sauerkraut, kefir, miso and kombucha.

Omega 3

Omega 3s are integral parts of the membranes that surround each cell in your body.

There are three forms of omega 3 fatty acids – EPA, DHA and ALA. ALA is what we call an “essential” fatty acid, which means that it must be consumed via our diet and cannot be made by the body.

A number of studies have shown that omega 3 is associated with boosted B-cell activity which is a vital part of our immune system.

We can make a only small amount of EPA and DHA from ALA, so it is still important to get it from our diet too. ALA can mainly be found in plant oils, nuts and seeds; and DHA and EPA, in oily fish.

Exercise

In addition to dietary measures that support your immune system, exercise may also play a role.

It has been found to enhance the body’s immune response and improve its defence activity. Regular, habitual exercise resets the immune system, something known as “immunoregulation”.

While the extent of this will clearly depend on the amount and type of exercise you do, the NHS guidelines are to incorporate at least 150 minutes of moderate-intensity activity a week or 75 minutes of vigorous-intensity activity a week into your routine.

Stress

While acute stress has been shown to be potentially beneficial for the immune system, chronic stress has been associated with the suppression of immunity.

Evolutionarily it is thought that an acute “fight or flight” type of stress caused a beneficial response in the immune system to prepare it for infections as a result of cuts, scrapes and bites.

Chronic stress, however, is associated with consistently raised cortisol production which is a hormone that suppresses the immune system to a degree.

Little is known about the psychological and biological pathways that link stress and the immune response, but the results of a large study have supported the association of stress and a decrease in immune measures.

Moderate your drinking

We are well aware that alcohol can have a damaging effect on many of our organs, leading to liver disease, and can also increase the risks for heart disease as well as a number of cancers.

But alcohol misuse can also weaken your immune system, making you more vulnerable to infections. If you are drinking more than the recommended limit of 14 units per week, perhaps consider trying to cut back.

Ultimately, in addition to our genetics, our immune system is made up of the interplay between our diet, stress, lifestyle and environment. While there are likely to be many more micronutrients and factors not mentioned above involved in the healthy functioning of our immune systems, there is no one elixir to optimise it, just the symbiotic relationship of all these factors acting together.