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Nutrition For Immune Health: What Does the Evidence Tell Us?

When considering the workings of the immune system, humility is required. It's fascinating, but also extremely elaborate, complex and filled with unknowns. There are a multitude of ways in which it can be activated, and several ways it can be supported.

The internet contains an abundance of information and advice on how to boost your immunity, a lot of which is based on dubious, minimal or non-existent evidence. It's also worth noting the error in semantics- we don't want to be 'boosting' our immune system. An activated immune system is a good thing if responding to a virus or ailment, but not something we want to induce or encourage long-term. If our immune system is boosted, we simultaneously induce processes such as inflammation, which can cause damage long-term. An overactive immune system is also a key factor in autoimmune diseases, where sufferers are actually desperate to downplay their immune response.

Immunology has been at the forefront of discussion during the covid-19 pandemic, with misinformation rife as a result. The dangerous and persistent flaws in reasoning perpetuated by people who suddenly fancy themselves as immunologists (thanks to the university of Youtube) are a significant threat to public health. One quick, easy way to detect a charlatan in this area is to ask them to explain the intricacies of the immune system. You could start by showing them a diagram such as this, and asking them to explain it to you:

And if they can't, you could point out that this diagram only covers the basics.

Moving on.


So, how can we support immunity?

Let's be clear, there is not one set of rules or recommendations that unequivocally protect every individual. But, maintaining overall good health through diet and lifestyle, alongside some potentially (but not bulletproof) forms of supplementation may assist our ability to fight off or cope with infections.


Metabolites (an intermediate or end product of metabolism) from Omega 3 have multiple functions when it comes to regulating our immune system. They can influence signalling between cells; bossing around immune cells by telling them which ones need to be activated and which need to chill out, so that we get a healthy, helpful response to infections and not one that makes us more inflamed, infected, itchy, pus-filled, etc. Their ability to regulate and lower inflammation (we DO want a level of acute inflammation in our immune response) helps us to combat the risk of inflammation becoming chronic and long-term, which can damage your tissues and lead to serious disease.

Intake of 250mg of of EPA & DHA per day covers this. For fish-eaters, this is equivalent to 2-3 serves of oily fish per week. The best ones to go for are represented by the acronym SMASH, which stands for Salmon, Mackerel, Anchovies, Sardines and Herring. If, like me, the thought of eating/smelling/being within 5km of fish makes you want to barf your eyeballs out, you can easily supplement. Just check the contents to ensure you’re hitting an adequate amount, as many brands don’t quite cut it.


Whilst there is some evidence that vitamin C supplementation may reduce the DURATION of the common cold, its ability to do so is not guaranteed. There’s certainly no harm in taking it during the onset and for the duration of illness, but if you’re continuing to grind yourself down to the ground with work/play, sleeping terribly and eating poorly alongside your illness, it’s not exactly going to touch the sides.

The recommended daily amount, which can be easily achieved through diet, is 100-200mcg.

If you are low in vitamin C or struggling with dietary intake, you can supplement.

Alternatively, you may have heard about mega-dosing vitamin C, touted by some as a miracle method for hitting illness on the head. This involves quantities of 1000-2000mcg, up to five times a day. There is limited scientific evidence to support this. It is, however, a highly effective way of giving yourself diarrhoea. And putting you at risk of developing kidney stones. DON'T DO IT.


Historically, vitamin D has been lauded for its positive influence on bone health. Without supplementation, our intake needs to mostly come from sunlight. The sun is so good at giving us the D that there has actually been a worrying increase in the number of children in Australia who have developed rickets as a result of being over-protected from sunlight.

More recently, research into the D has uncovered immunomodulating effects. Specifically, the discovery of many immune cells containing vitamin D receptors. Translation: it can latch onto immune cells, have a little chat about what’s going down and then get them to work on busting out an immune response to infection. Vitamin D can influence both the innate and adaptive immune response- but what the heck are those?

Innate immune system: the one that gets into action at the first sign of infection, acting as a barrier, multiplying in numbers to attack a foreign invader, creating inflammation, exploding and killing invaders, forming pus and mucous and eating foreign invaders then pooping out their parts to display on their surface. Cool!

Adaptive immune system: A little slower to act, but it’s more specific and responds to a pathogen that’s presented to it. If it’s something the body hasn’t encountered before, such as your first round of chicken pox, it’ll help to build cells and antibodies that recognise that pathogen next time and kill the heck out of it before you develop any symptoms.

Maintaining adequate vitamin D status is required for these immunological benefits. If sufficient sunlight isn’t available, such as in the UK from October to March, you should supplement. The NHS recommendation suggests 400IU/10mcg, but 1000-2000IU is likely to be of more benefit (and is still well within the safe range).


It is true that zinc plays a strong role in good immune health, and that even a mild deficiency may have a negative impact on our immune response.

This can mean our immune cells don’t form properly, can’t be activated to do their job, that cells we need to create antibodies won’t mature, that inflammation can get out of whack, and that our immune cells won’t be able to find, eat and explode the shiz out of pathogens as effectively as they normally do. So, maintaining adequate zinc status through a generally healthy diet is important.

Supplementation, on the other hand, is not so simple. In particular, long-term zinc supplementation as a preventative for illness is actually NOT recommended. Taking too much and for too long can actually lead to copper deficiency as well as, ironically, causing poor immune function!

Instead, zinc can be supplemented within 24 hours of symptom onset and only for the duration of illness, particularly if it’s the common cold. In this instance, there is decent evidence to suggest it can reduce the duration and severity of illness, as well as improving recovery.

Type of zinc and dosage are important here: the most effective form seems to be ZINC ACETATE LOZENGES at a dosage of 75mg per day.


Now for the annoying part: singular nutrients, in supplement or food form are unlikely to have any impact whatsoever if your overall diet is a bit of a trainwreck.

From a dietary perspective, overall intake that is associated with lower inflammation is likely to be supportive of immune function. It also means a diet that supports your gut function, as a healthy gut also impacts your immune health. This means the diet contains (but is not limited to):

🐠 Fish, particularly oily fish

🥑 Unsaturated fat eg. plant-based oils

🍞 Whole grains

🥛 Dairy

🍎🥦 Lots of vegetables and fruit, in a variety

🥜 Nuts

🧆 Legumes eg. chickpeas, lentils

This isn’t to demonise sugar or fat, or foods that are deemed ‘bad’ or ‘processed’. Attempting to cut them out altogether is often counterproductive due to the stress involved.

However, a diet containing high levels of sugar and saturated fat that is lacking in fibre and the foods listed above isn’t great for your immune health (amongst other health factors). It also puts you at high risk of developing obesity and/or chronic inflammation, both of which are capable of altering your immune function and increasing your risk of illness and complications related to illness.


Alongside decent nutrition, adequate sleep is crucial for healthy immune function. If you're not getting enough (7-8 hours per night) then you've got a good chance of being more susceptible to illness, unfortunately.

Regular exercise also aids immune function. This is because it improves the immune response to infection, lowers your illness risk, reduces your stress response and reduces inflammation. By increasing your blood flow, it also helps to circulate immune cells around the body.

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