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Your immune system needs your help in protecting the body from viruses, from keeping a healthy diet to getting plenty of sleep and keeping your stress levels low. Photo: Getty Images

Explainer | What is the immune system and how do you strengthen it? Expert tips on boosting your defences

  • Your immune system needs your support to protect your body. This includes things like maintaining a healthy diet, exercise, getting enough sleep and not smoking
  • A strong immune system might stop us from contracting, or minimise, a cold or Covid-19 – it may even help us when we face diseases such as cancer or dementia

You’ve heard this word a lot in the last two years: immunity. And you’re going to be hearing it a lot this winter, as Covid-19 and its latest mutation carry on just as flu season begins.

Immunity is the protection our immune system delivers. Made up of cells, antibodies and chemical mediators that protect the body from infections, that system includes multiple layers and barriers – like your skin and the cilia, or tiny hairs, that line your airways – as well as special cells that recognise and attack viruses and bacteria. These ranks of protective elements work together to support your overall well-being.

Dr Adrian Wu Young-yuen, a specialist in immunology and allergy in Hong Kong, says you should think of the immune system like a small internal army. It needs your support to do the work of protecting the body, though, in the form of “the usual healthy lifestyle choices”, he says.

These include a healthy diet, sufficient exercise, rest and sunshine, and not drinking alcohol or smoking.
Dr Adrian Wu Young-yuen is a specialist in immunology and allergy in Hong Kong.
Sleep is important, Wu says, because without enough, our bodies do not get the necessary restorative downtime, and we stop making enough of the protective proteins called cytokines that our immune response relies on to battle infection or inflammation.
Managing stress is key. Stress prompts the production of the hormone cortisol which can cause or exacerbate inflammation, a precursor to many illnesses. Unrelenting stress, or stress that left unchecked becomes chronic, interferes with our white blood cells’ defences.

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Dr Paul Clayton, a leading UK scientist in the field of nutrition and author of Strengthening Your Immune System: How to Fight Infection, Allergy and Autoimmune Disease, sees our diet as the most important factor in promoting a resilient immunity.

In our busy, modern world, though, we are not only eating too little of the “right” whole foods, we are eating too much of the wrong ones that are highly processed and full of fat and sugar. The immune system doesn’t fight well on an empty stomach or one filled with empty calories, Clayton says.

A poor diet is actually detrimental, compromising health and predisposing us to four conditions that impair immune function: chronic inflammation; Type B malnutrition – because we’re not getting enough of the right foods; “dysbiosis” – a disruption in the important but delicate balance of microbiota in our gut; and glycative stress, in which excessive amounts of sugar molecules accumulate in the blood and tissues, and bind to inappropriate targets.
Dr Paul Clayton is a leading UK scientist in the field of nutrition.
We cannot fast-track our way to super immunity by popping extra supplements such as vitamin C and echinacea, the purple flowering plant used in traditional medicines. Clayton stresses that taking vitamin C can only improve aspects of immune function in those who are deficient or depleted in this vitamin. If you have enough, taking extra will have little, if any, effect. Our bodies can only absorb so much of it, and excess is expelled in the urine.

As for echinacea, research shows it increases the number of white blood cells, which fight infections, but Clayton says it may not be the best tool for the job.

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Clayton says: “The most intensively researched and proven molecule, or more strictly, group of molecules, are the 1-3, 1-6 beta glucans derived from Saccharomyces cerevisiae” – baker’s yeast or brewer’s yeast, basically. Studies have shown that taking these increased the body’s potential to defend against invading pathogens.

We are born with a functioning immune system – the innate immune system. Its key components are macrophages and natural killer (NK) cells. They patrol the body on the lookout for anything that doesn’t belong.

If macrophages spot a germ, they swallow and try to digest it. If NK cells see a virally infected cell or a cancer cell, they will kill it to stop it from producing more viruses, or replicating.

A robust immune system can help protect us from, or minimise the impact of, an illness like the common cold or even Covid-19. Photo: Getty Images

The innate immune system takes action the moment it is aware of a pathogen’s presence and is our first line of defence. The adaptive immune system is the second line. It is the one with the memory function, involved in immunisation, allergy and autoimmunity. Once this system has learned to identify an enemy, after an initial infection or vaccination, it remembers the enemy’s characteristics. On second exposure, the memory cells recognise it and generate an immune response involving weapons such as antibodies.

“With time, you will be exposed to various pathogens which may or may not cause symptomatic illness,” Clayton says. “With each exposure your repertoire of memory cells increases, as does your ability to mount specific immune defences to those pathogens.

“Some elements of the immune system decline with age. This was previously thought to be intrinsic and unavoidable – but new research indicates that it is in fact due in large part to our diet and lifestyle.”

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Herd immunity – a phrase that has been repeated often in the last two years – means having a large enough proportion of a population that has retained the cellular memory Clayton refers to, and has gained immunity to stifle a pathogen’s spread.

How powerful can immunity be? A robust immune system might protect us from, or minimise the impact of, an illness like the common cold or even Covid-19, when our immune system is layered up by vaccine and exposure to the virus if we’ve had it. But it may even help when faced with dreaded diseases such as cancer or dementia.

That is why Clayton suggests addressing all factors that detract from optimal immune health: stop smoking, fight obesity, get active and control chronic stress.

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Dr Paul Clayton’s immunity boosting tips

  • Make sure your diet includes important vitamins and minerals, including those 1-3, 1-6 beta glucans found in brewer’s yeast, and a substance known as isothiocyanate that is found in cruciferous vegetables including bok choy, broccoli, cabbage, cauliflower, kale and Brussels sprouts. Vitamins C and D, and the trace elements zinc and selenium, are also key.

  • Take regular medium-intensity exercise.

  • Maintain a healthy body weight.

  • Switch from ultra-processed foods to basic produce, and learn how to cook if you don’t already know how.

  • Reduce stress in your life. If that is not possible, use an adaptogen – a natural substance that helps the body adapt to stress – from, for example, panax ginseng, ashwagandha or saffron.

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