An Immunologist’s Guide To Looking After Your Immune System

Looking after your immune system has never been more important, but in between supplements, nutrition and mental health, it’s not always easy knowing where to start. To understand what really matters, we went to Jenna Macciochi, one of the UK’s leading immunologists. Here’s what she had to say…

Vitamin D Is Imperative

“Vitamin D is a key regulator of immune function and most immune cells express the vitamin D receptor meaning they are directly responding to levels of this vitamin in the body. It is an important component of our first line defence – keeping body barriers like the skin, lungs and gut strong. Vitamin D also increases immune cells called T-regulatory cells, which play a major role in keeping the immune system in check. There is a large body of evidence supporting a role for vitamin D in reducing the risk of viral respiratory tract infection. Low vitamin D status has been noted in severe cases of COVID, but clinical trials are still underway to understand the relationship. Even if COVID turns out not to be a reason to take Vitamin D, it is a safe and effective way to support immunity. Anyone living in the UK is at risk of deficiency during the winter months and PHE now recommends taking 10micrograms/day (400IU/day) year-round to support general health.”

But Don’t Forget About Vitamin C

“Vitamin C is also an important vitamin when it comes to your immune system. In fact, your need for vitamin C rises dramatically when you are fighting an infection. However, it is found in a wide range of foods so if you are eating a balanced diet and getting plenty of fresh produce, it’s not something that’s necessary to supplement with every day. There is some evidence that supplementing upon the onset of symptoms may reduce the duration of the common cold. However, it’s important to note that at doses above 400mg per day, we start excreting vitamin D in the urine and taking more than one gram per day can cause nausea, leaky gut and abdominal pain.”

Up Your Omegas

“It could be worth taking an omega 3 supplement, especially if you aren’t eating oily fish regularly. The key things to look for in a supplement is a marine omega-3 that contains two specific essential fatty acids called eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). This is much more bioavailable than the form found in some nut and seed oils which is called alpha-linolenic acid (ALA). Try to avoid omega 3 from krill products because there are some environmental concerns. Instead, look for brands that are transparent about using small oily fish from sustainable sources – I rate Bare Biology. It’s also worth checking for an International Fish Oil Standards (IFOS) rating. A high rating ensures the supplement is free from contaminants and of maximum purity, as well as containing a high concentration of the valuable EPA and DHA omega 3s.”

Prioritise Your Gut 

“It’s vital to nurture your microbiota – the collection of gut bugs that live on and in you – as it plays an important role in the overall function of your immune system. It can be helpful to support the natural balance of these, particularly during periods of stress or when it may be disrupted by illness. It’s important to remember the digestive tract starts in the mouth. Every time you swallow, you’re swallowing thousands of bugs – some bad but, most importantly, some good. Contrary to what you might think, the goal isn’t to kill off all the germs in your mouth. In fact, just like the gut microbiota, the good bacteria in your mouth support not just the health of your oral cavity, but they also support and train your immune system. Consider opting for a gentle oral care product such as Zendium, a first-generation toothpaste that delivers a prebiotic effect, which supports the oral microbiota, in turn helping to keep your immune system strong and healthy. Zendium is also free from harsh ingredients such as sodium lauryl sulphate, known to damage the delicate balance of bugs.”

Think About Fibre

“Your gut microbes love to eat dietary fibre. When they do this, they educate your immune cells, support their function and spark signals that dial down inflammation.  On a practical level, the higher diversity of plant fibres you consume, the better you are actively nourishing your immunity. Protein is also important for enabling the body to mount an appropriate immune response, making antibodies and repairing and growing the body’s tissues. Plant-based sources of protein like beans and pulses are conveniently packed with lots of gut-loving fibre as well as a sustainable source of protein.”

Avoid A Fat-Free Diet

“Fats play lots of important roles not only in your immunity but also more broadly in your health. For example, fats are needed for the absorption of vitamins A, D, E and K; can help with blood sugar regulation; are needed for the production of some hormones that play a key role in the immune system; and they help resolve inflammation. There are many different types of fat, but omega-3s are considered essential. If you aren’t regularly eating oily fish, you should be supplementing with omega-3s.”

Chronic stress can be detrimental to your immune system, leaving you more susceptible to infections and even raising your risk of some chronic inflammatory diseases.

Don’t Forget Micronutrients 

“Your immunity can be impaired with a micronutrient deficiency. Try to include the following in your diet:

  • Dark green vegetables: The likes of kale, chard, spinach, rocket, Brussels sprouts and sprouting broccoli all provide a variety of beneficial phytonutrients, fibre, vitamin A, magnesium, folate, magnesium and more. If there is one thing to add to your diet, it is this group of vegetables. Aim for at least one portion per day – remembering that when cooked, they tend to shrink considerably in terms of volume, making it easier to achieve this target.

  • Red, orange and yellow foods: These are a great source of vitamin A. Vitamin A is also a fat-soluble vitamin, so try roasting these with a healthy fat like olive oil.

  • B vitamins: The vitamin B complex contains eight vitamins; they are water soluble and essential for the healthy balance of the immune and nervous systems. They are found in seafood, eggs and dairy as well as legumes, leafy greens and seeds. 

  • Allium vegetables: Foods like garlic, leeks and onions as well as cruciferous vegetables like rocket, broccoli, cabbage, cauliflower and kale are great sources of sulphur, which has several health benefits, including reducing inflammation and a reduced risk of developing certain chronic health conditions like cardiovascular disease.

  • Nuts and seeds: These are easy to add to meals to increase nutrient quality – they are full of important minerals like magnesium, zinc and selenium.”

Don’t Over-Exercise

“Too much exercise can be bad for the immune system. Exercise is a form of stress – whether it’s a heavy training session, worrying about a deadline or running for our life, we only have one stress response. Too much exercise induced stress from a heavy training session or prolonged strenuous exercise without adequate recovery will have the biggest negative impact on your immune system. There can be tell-tale signs you are creeping into this category: feeling exhausted from your usual training, starting to dread gym sessions, muscle wasting despite training, and feeling exhausted irrespective of rest and recovery.”

Consider An Outdoor Workout

“Your outdoor environment can influence your microbiome.  We share bugs with the places, people and spaces that we interact with. Green space tends to have the best microbial diversity, so it makes sense to take your workouts outdoors as there are plenty of other benefits of green space including stress reduction and fresh air.”

Listen To Your Body

“When your immune system is fighting an infection it actually instructs your brain to change your behaviour – this includes things like lethargy, social withdrawal and changes in appetite. By accepting these and getting the rest you need, it’ll give you the best chance of getting quickly back to full health, and avoids passing on germs to others. Pre-COVID presenteeism at work was very common; now people realise how easily we pass on germs and stay home when sick. Supplementing with vitamin C and zinc can also be useful as your immune system requires these micronutrients in huge doses when fighting an infection. Supplementation upon the onset of symptoms has been scientifically shown to reduce duration and severity of upper respiratory tract infections. Hydration is also important – this keeps your lymphatic fluid flowing, helping immune cells to move around the body.”

Avoid Stress Where Possible

“Chronic or frequent intermittent stress – if not managed properly – can be very detrimental to your immune system, leaving you more susceptible to infections and even raising your risk of some chronic inflammatory diseases. There is also an indirect negative effect because when we are stressed, we tend to sleep badly and engage in negative lifestyle behaviours like eating unhealthy foods and drinking more alcohol. Regular meditation, mindfulness and self-compassion can help future proof your body against the impact of stress, but these are not always practical in a stressful moment. The most immediate tool is just breathing, making an effort to extend your exhale. Narrowly focusing your eyes is also not conducive to relaxation, so aim to widen your gaze to a panoramic vision. A simple way to do this is to get outside in green space.”


Jenna is currently partnering with immune boosting oral care brand Zendium, the number one brand trusted by dentists in Scandinavia which has recently launched in the UK. For more information visit and


DISCLAIMER: Features published by SheerLuxe are not intended to treat, diagnose, cure or prevent any disease. Always seek the advice of your GP or another qualified healthcare provider for any questions you have regarding a medical condition, and before undertaking any diet, exercise or other health-related programme.

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