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How to strengthen your immune system

25 March, 2020
Healthy Food

We’ve all heard about the importance of diet and disease, with the common cold and influenza being no exception. Complimentary approaches have seen wider uptake as the popularity to reduce unnecessary pharmaceutical use continues. 

Common nutrients like zinc, vitamin C, vitamin D, selenium, garlic, echinacea and probiotics are popular in the supplement industry at the moment. But does the strength of evidence for the use of complimentary medicines and herbs warrant replacing pharmaceuticals altogether? 

Research is advancing in the area of the gut microbiome and its role in immunity. We consulted the professionals at Microba and Jenn Madz, CBHS’ Accredited Practising Dietitian, to share some insight into the evidence of diet versus pharmaceutical approaches towards coping through times of health crisis.

According to Christine Stewart, Microba’s Nutritionist, Registered Nurse and Microbiome Coach, it’s key to maintain your immune system throughout every season. She explains that in times of health events, it’s important that the immune system has been built up through gut bacteria and diet.

With growing concerns around COVID-19 and how to stay protected, the immune system has become a hot topic. Unfortunately, while no one can promise you immunity from certain diseases or illnesses, you can take steps to keep your immune system functioning well. Diet is one of those steps.

Why is your immune system important?

Most people will have a basic understanding of the immune system and what role it plays in the body.

Your immune system is a form of defence against the ‘bugs’ which can cause illness − pathogens or disease-producing microbes. When your immune system detects a pathogen, it launches its defense mechanisms to neutralise the invader and protect healthy cells from infection. If infection does occur, the same system helps your body recover by leaving behind a permanent memory of the pathogen – this is called adaptive or acquired immunity. Over time, this ongoing recollection and identification of pathogens provides greater protection and results in fewer infectionsi

More recently, focus has shifted onto the gut microbiome for the role it plays in supporting the immune system, along with many other important bodily functions. This is partly because your gut microbiome – the community of microorganisms living in your gut – can produce substances that impact your immune system. Studies suggest that a diverse and well-balanced gut microbiome can help support the immune system.

Your gut health and immunity

Your gut bacteria are heavily involved in many important bodily functions from regulating your appetite and glucose levels, to influencing your mental health and immune system.

The gut microbiome and gastrointestinal tract is a potential entry site for pathogensii. The bacteria inhabiting this area play a vital role in not only digesting your food, but in preparing and training the immune systemii.

These bacteria interact with potential pathogens and protect your gut lining (barrier immunity) through the process of colonisation resistanceiii, iv, v, vi. Colonisation resistance basically means that harmful bacteria are prevented from living in the gut through the competition for space and nutrients.

The way your gut interacts with your immune system is through the production of substances called short chain fatty acids (SCFAs). The most well-known of these are butyrate, propionate and acetatevii. They are thought to be highly beneficial for the immune system as they have the ability to reduce inflammation and can help to support immunity. They can assist in mounting a defense against invading pathogens and preventing inflammation in the gut when they team up with your intestinal cellsviii. These SCFAs also have the potential to boost immunity (either systemic or whole-body) during an immune response. They do this by enhancing gut barrier function and recruiting immune cells to fight against invading pathogensviii, ix. If you do not have good levels of gut bacteria that are able to produce adequate amounts of SCFAs, your immunity could be affected.

You can support your bacteria in producing these important substances by making sure your diet includes an assortment of prebioticsvii. Prebiotics are transported by your human enzymes to your large intestine where they are fermented by your gut bacteria and assist in producing beneficial substances such as SCFAs x,xi. Examples are resistant starch and pectin.

When you feed your body foods that are rich in fibre, you are supporting the beneficial bacteria in your gut to produce SCFAs that can support your immunity and overall health.

How can you support your immunity through diet?

Plants, plants and more plants! Your gut bacteria love to eat plant-based foods such as fruits, nuts, seeds, vegetables, legumes and wholegrains. These prebiotics will help fuel the beneficial bacteria in your microbiome and, in turn, can support your immune system.

Jenn Madz, CBHS’s Accredited Practising Dietitian and Wellness Program Coordinator, explains that maintaining your immunity year-round requires a proactive approach and a consistently healthy diet, to activate immunity pathways using gut bacteria.

According to Jen, “In times of illness, people reach out for supplements and the like, but unfortunately taking supplements doesn’t always achieve better results than healthy food choices. You must feed your gut bacteria with the fuels they need. To keep your gut microbiome balanced, your diet needs to be as diverse as your bacteria. It’s even more important for members of vulnerable groups (such as children, people with existing health conditions, the elderly, pregnant women and those who are immune-suppressed) to eat a healthy and diverse diet and work on feeding their gut microbiomes. If you’re concerned about your welfare, you should seek advice from a healthcare professional.”

A bowl of salad

What vitamins do your immunity pathways need?

So, lets clear up the confusion.  We certainly need the following for our immunity pathways to help protect us:

  • Vitamins: A, D, C, E, B6, B12
  • Folate
  • Zinc
  • Copper
  • Selenium
  • Magnesium and iron

But taking a supplement won’t cure or prevent you from contracting COVID-19 or any other viral disease for that matter. Make sure you aren’t deficient in any of the above by maintaining a healthy diet high in these nutrients that come with a range of fibres. This approach looks to be the more successful way you can support your immunity.

All immunity pathways require certain vitamins and minerals to make them function, which is why a lot of supplements may claim to be linked to immunity.  But the truth is, unless you’re deficient in these nutrients, taking larger doses during times when you want a stronger immune system isn’t necessarily going to speed up those pathways or make your immune system stronger.

So, what’s the takeaway? Start with diet and nutrition, and focus on giving your body (and your gut) the nutrients it needs to function at its best. Speak with your healthcare professional for advice specific to your situation or if you have any deep concerns.

Day on a plate

Check out these suggestions for your gut and your immune system from expert dietitian and nutritionist, Jenn and Christine:

Breakfast – Bircher muesli made with a high protein Greek yoghurt topped with a mix of your favourite seeds and some cinnamon for flavour. Try adding berries for a boost of polyphenols.

Lunch – Roast beetroot, pumpkin or sweet potato added to a green salad topped with some lean protein like a salmon fillet (tinned/pouch is okay) or poached/grilled chicken breast.

Dinner – Try buckwheat or brown rice in your favourite curry with added chickpeas, mixed beans and hard tofu.

Snacks – Choose seasonal fruits, a selection of nuts and seeds or roasted fava beans for a salty touch.

Co-written by:

Christine Stewart, Nutritionist, Registered Nurse, Microba Microbiome Coach
Jenn Madz, Accredited Practising Dietitian and Wellness Program Coordinator for CBHS

All information contained in this article is intended for general information purposes only. The information provided should not be relied upon as medical advice and does not supersede or replace a consultation with a suitably qualified healthcare professional.


i Simon AK, Hollander GA, McMichael, A. Evolution of the immune system in humans from infancy to old age. Proc. R. Soc. B, 282 (2015). Doi: 20143085.

ii Belkaid Y, Hand TW. Role of the Microbiota in Immunity and Inflammation. Cell. 2014; 157:121-141

iii Lawley TD, Walker AW. Intestinal colonization resistance. Immunology 138:1-11 (2013). Doi: 13:790-801.

iv Kamada N, Seo S, Chen GY. Nunez G. Role of the gut microbiota in immunity and inflammatory disease. Nat Rev Immun. 2013; 13:321-335

v Buffie CG, Pamer EG. Microbiota-mediated colonization resistance against intestinal pathogens. Nat Rev Immun. 2013; 13:790-801m

vi Sassone Corsi, Martina & Raffatellu, Manuela. (2015). No Vacancy: How Beneficial Microbes Cooperate with Immunity To Provide Colonization Resistance to Pathogens. Journal of immunology (Baltimore, Md : 1950). 194. 4081-4087. 10.4049/jimmunol.1403169.

vii Rios-Covian D., Ruas-Madiedo P, Margolles A. Gueimonde M, de los Reyes-Gavilan C G, Salazar N. Intestinal short chain fatty acids and their link with diet and human health. Frontiers in microbiology. 2016;7:185.

viii Corrêa-Oliveira R, Fachi JL, Vieira A, Sato FT, Vinolo MAR. Regulation of immune cell function by short-chain fatty acids. Clin Transl Immunologyl. 2016;5: e73.

ix Kim CH, Park J, Kim M. Gut microbiota-derived short-chain fatty acids, T cells, and Inflammation. Immune Network. 2014;14(6):277-288.

x Gibson, Glenn, R. et al. Dietary modulation of the human colonic microbiota: updating the concept of prebiotics. Nutrition research reviews, 17(2): 259-275 (2004). Doi: 10.1070/NRR200479.

xi Roberfroid, M. Prebiotics: the concept revisited. The Journal of Nutrition, 137(3): 830S-837S (2007). Doi: 10.1093/jn/137.830S.


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