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.
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.
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.
What would be then?
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.
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.”
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.
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.