With coronavirus likely to be with us for the foreseeable future and flu season here already, there’s a lot of talk around “boosting” our immune systems.

“Whilst it may seem semantics – and I’m aware of professionals using this term, too – the language is key,” says nutritionist Nadia Felsch. “‘Boosted’ in this sense is often [intended to mean] ‘strengthen’ or ‘support’, which are far more appropriate terms.

“A ‘boosted’ immune system is actually a state we don’t want our body to be in. A ‘boosted’ immune system is one that can also be described as over-active.” That is, we want our immune systems functioning normally – an overactive immune response is not a good thing, and can even lead to autoimmune disorders.

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When people talk about “boosting” or “bolstering” immunity they are really referring to supporting your immune system – the network of cells, tissues and organs that defend your body against infection – to function as best it can. And protecting and optimising your immune system is a totally different thing from “having immunity”. Having immunity means a person’s body contains certain antibodies to combat a specific virus as it tries to take hold.

It’s important to be cautious about unfounded advice in this space, especially given the lack of regulation in the wellness industry and the misguided idea that, by eating right or taking vitamin supplements, one could build some sort of forcefield against infection – you can’t. Many doctors and nutritionists bristle at use of the word "boost" to talk about immunity for just this reason.

In other words, an optimally-functioning immune system will not prevent you from contracting Covid-19 – for which there is currently no vaccine – or other viruses such as the flu. But making sure your immune response is functioning as well as it can is one way to help your body fight infection when it does happen.

So, what can you do to make sure your immune response is as good as it can be? Does meditation help? Should you be taking certain vitamins? What about exercise? And what are the myths to be aware of?

We spoke with a doctor, a sleep expert and a nutritionist about the concrete, everyday things you can do to help – many of which can be done without leaving your home or purchasing anything – and things that won’t really help at all.

Professor Danny Eckert: get outside, get moving and get enough sleep

Danny Eckert, a professor in the College of Medicine and Public Health at Adelaide’s Flinders University and the director of the Adelaide Institute for Sleep Health, says there are three vital pillars that strengthen the multiple components of the body’s immune response: “exercise, diet and sleep”.

Insufficient sleep – that is, less than eight hours a night – and excessive alcohol consumption can negatively impact your immune system, Eckert says. He cites a 2009 study in which people exposed to the virus that causes the common cold were five times more likely to contract it if they’d slept less than seven hours a night or had poor sleep.

Regular aerobic exercise outside, such as brisk walking, cycling, running, or swimming, also helps to strengthen the body’s immune response, he adds.

Getting the body moving isn’t just important for your physical health – it’s almost important for your mental wellbeing, and psychological factors have been shown to contribute to the overall wellbeing of the immune system.

Stress is the immune system’s enemy, Eckert says, as it’s inflammatory and can increase the level of the hormone cortisol. Cortisol is harmful, Eckert says “[because the body] gets used to it and stops responding in the protective way that it should, [decreasing] the ability to lower inflammation and decreasing white blood cells (lymphocytes), which help fight infection.” Over time, long-term stress can take energy away from the body’s normal processes, leaving it less able to defend itself.

While indoor exercise is beneficial, being outdoors means you also get a much-needed dose of Vitamin D, which has a positive effect on your immune system and response. Don’t spend too much time soaking up rays though, Eckert says. He recommends “just a few minutes outside on most days of the week”.

Vitamin C can also be helpful in immune support, he says, but is best obtained from a well-balanced diet rather than loading up on supplements. And it’s important to note that the vitamin’s mythic status as a cold and illness preventative is overblown.

Doctor Femke Buisman-Pijlman: reduce stress, as psychological factors impact your immune system health

Like Eckert, Dr Femke Buisman-Pijlman says getting enough rest, eating well, exercising and reducing stress all play a part in keeping your immune system strong and healthy. The associate professor at the University of Melbourne and specialist in pharmacology also emphasises that psychological factors are proven to play a part in the overall wellbeing of the immune system.

“The immune system is made up of a very extensive system of proteins and cells that circulate in the body and brain,” she explains.

Our immune system doesn’t “function alone”, rather, it works in concert with other systems such as the central nervous system and the stress system (known as the hypothalamic-pituitary-adrenal axis, or HPA axis).

“Research has shown that some mental health problems are associated with, or may even result, from an imbalance in specific factors in the immune system,” says Buisman-Pijlman. “So, your psychological state is clearly linked to how well your immune system can respond, and this also works in the other direction. Feeling down when you are sick is an example of this.”

Even a temporary lull in stress triggers can have a positive impact on health and wellbeing, she says. The hormone oxytocin, for example, associated with feelings of wellbeing, love and bonding, can be produced through exercise and physical contact, and is one source of stress reduction.

Nutritionist and naturopath Katrina Schilling: eat a nutritious diet and avoid processed foods, alcohol and smoking – and try meditation and mindfulness to alleviate stress

“The immune system depends on a broad spectrum of things to thrive, including nutrients from food, homeostasis, which is the biochemical balance of hormones, and commensal microbiology, which is the healthy populations of microorganisms in and on the body,” nutritionist Katrina Schilling says.

She highlights the importance of caring for your
gut microbiome population” in supporting healthy immune function. Meaning? Looking after “the community of bugs living in the human gastrointestinal tract and their genes”. (She cites two recent studies that demonstrate how intestinal microbes support and regulate the immune system and response.)

“Minimise processed foods lacking micronutrients and fibre; avoid diets high in animal protein, fat and refined sugars; avoid excess alcohol, smoking, heavy environmental pollution and a sedentary lifestyle,” Schilling recommends, as these things can negatively affect the development of vital gut microbes.

Eating nutrient-rich fresh vegetables and fruits as well as nuts, legumes and whole grains will support gut health, she says. Grapes, berries, cocoa and grains (which contain polyphenol micronutrients, which are full of antioxidants) are particularly good in this regard.

Schilling also recommends consuming moderate amounts of safely-produced fermented foods – which are full of digestive-tract strengthening probiotics – such as yoghurt, kimchi and sauerkraut.

With approval from your doctor or pharmacist, Schilling says you can also look into taking probiotic supplements that contain lactobacillus and bifidobacterium. Speaking of supplements, she warns against the common myth that “more is better” in terms of higher percentages in a vitamin.

“This couldn’t be further from the truth. Looking for the biggest number on the front bottle label may not be doing you any favours and may not even correlate to the actual active content. In fact, it can be harmful to supplement one’s diet if the added level of mineral, vitamin or probiotic isn’t needed.”

Instead, Schilling says that supplement quality matters above all – it’s important to “make sure the product is of high quality and actually contains the ingredients on the label”.

Vitamin D and zinc are two nutrients “commonly linked to healthy immune function, increased anti-microbial peptides and defence against infection,” she says. The former can be obtained from safe sunlight exposure, as well as oily fish, eggs, fortified milk and some mushrooms. The latter can be found in sunflower and pumpkin seeds, whole grains, egg yolks, oysters, beef and bilberries.

Schilling, like Eckert and Buisman-Pijlman, is also a big advocate for reducing stress to help strengthen the immune system. She recommends meditation and walks in nature to relieve anxiety and tension, and points to the Japanese practice of shinrin-yoku, or forest bathing – which involves short, leisurely forest visits – as a particularly enjoyable way to do this. It’s “been shown to reduce stress biomarkers” and increase the population of cells that would combat a virus, she says.