How to boost your immune system with food

“You are what you eat.” How many times have you heard that? As it turns out, when it comes to boosting your immune system, it just might be true!

What is an immune system?

We’ve all heard about the immune system, but what exactly is it?

The immune system is a complex network of cells and proteins that defends the body against infection… Abnormalities of the immune system can lead to allergic diseases, immunodeficiencies and autoimmune disorders.

Better Health, Victoria State Government

In other words, your immune system is one of your body’s top defensive measures against allergic diseases, immunodeficiency and auto-immune disorders.

Intro to Microbiomes

What are microbiomes?

Also known as gut microbiota, microbiomes are made up of a complex system of bacteria, viruses, genes and other microbes that colonise the GI tract. GI tract being the “gastrointestinal tract”. The number of bacterial cells are thought to be in the trillions. Roughly ten times MORE than the number of human cells.

Image shows a cartoon depiction of the microbiota in your gut and immune system.
There’s an entire microbiome in your gut! Image source: Sci-News

Every single person’s biome is unique. Your individual biome is individual to you, and like nobody else’s. In fact, your own biome isn’t even the same as your own biome last week, month or year. The microbiome is not static.

There are numerous factors that can influence and affect one’s microbiome.

  • Genetics
  • Birth
  • Diet
  • Sleep patterns
  • Levels of stress
  • Use of anti-biotics
  • Use of drugs
  • Smoking
  • Exercise

Why is it so important?

Improves immunity

Your biome actively helps your body to fight viruses and infections. A healthy gut biome is more effective at keeping your body immune from outside infections.

Use extra nutrition

Microbiomes work to harvest extra nutrition that you take in. This leads to better health and easier weight management.

Weight regulation

A healthy biome can help you regulate your weight better and with stronger long term effects. By controlling the hunger signals you may otherwise be experiencing, your biome works to curb your cravings by assisting in blood sugar regulation.

Production of vitamins

Of course it’s not just vitamins! Microbiomes make amino acids, hormones and neutrotransmitters as well.

Tough fibre digestion

An important function of the microbiome is to digest the tough fibres found in many of the plant foods we consume. The bacteria contained in your gut feeds on the fibre, breaking it down and helping digest it.

Uses indigestible food

Food that is consumed but cannot be digested is turned into a wide range of hormones and chemicals by the microbiome.

Butyrate production

Biomes produce butyrate, a fatty acid that is protective against bowel cancer and numerous other diseases.

CNS interface

Last but not least is communication with the Central Nervous System (CNS). This is especially important in regulating and maintaining healthy levels of chemicals and hormones in our body.

Click here to find out more about how the microbiome and food can affect your mood.

How to eat to keep your biome diverse and immune system strong

Traditional vs Western diets

When you compare the traditional Mediterranean diet to the typical modern Western diet, there is a stark, confronting difference.

The Western diet, made up of highly refined and processed foods, encourages a lot less gut diversity. While the Mediterranean diet, full of plant-based foods, ranks among the best diets in the world for longevity and health.

Why? Because when it comes biome wellbeing, diversity is key.

The more diversity, the greater the difference

The more types of different plants you eat, the greater the diversity of your biome. This is why the traditional Mediterranean diet gets such top marks. It includes a wide range of any or all of the following:

  • Huge diversity in salads and vegetables
  • Legumes
  • Fruits
  • Wholegrains
  • EVOO
  • Greek yoghurt
  • Nuts
  • Seeds
  • Olives
  • Fish
Image shows different types of consumable legumes for boosting your immune system.
How many types of legumes can you name? Image source: Healthline

Foods that are better consumed in lesser amounts feature far less heavily in such diets. This includes:

  • Fermented cheeses
  • Wine (always with meals)
  • Butter, cream and milk (these are never used except for milk in coffee and for infants)
  • Red meat

Positive foods for boosting your immune system

The foods that positively influence your gut flora (i.e. the bacteria and other organisms that exist in your biome) can be split into two categories:


Prebiotics are food for the bacteria in our guts. FODMAP* and elimination diets seek to improve the GI symptoms such as reflux, IBS (irritable bowel syndrome) and suspected food intolerances.

Examples of prebiotic food include:

  • Dietary fibre such as as fruits, vegetables, nuts, seeds and wholegrains
  • Herbs and spices e.g. turmeric
  • Indigestible carbohydrates
  • Asparagus, Jerusalem artichokes, garlic, onion, bananas, barley, oats, apples, cacao, flaxseeds, seaweed, Chicory root, and dandelion greens
  • Cruciferous vegetables such as cauliflower, Brussel sprouts, kale, broccoli and cabbage
  • Resistant starches such as lentils, peas, oats, beans, cooked and cooled potato, cold past salad, firm bananas and wholegrain foods

HINT: If you’re thinking about adding prebiotic food to your diet, think variety and colour!


Probiotics are living microorganisms that are consumed in various fermented food. Properly fermenting food for consumption is an ancient craft and a tried and true method for unlocking beneficial and good gut bugs.

* FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols.

Examples of fermented food include:

  • Sauerkraut – this fermented cabbage dish is also a rich source of Vitamin C. It helps stimulate the production of white blood cells, increase cellular regeneration and repair and help formulate collagen.
  • Kimchi – made up of fermented wombok, this Korean alternative includes chili, onion, garlic and ginger.
  • Sourdough bread – as a low GI option, traditionally made and naturally fermenting dough is great for your microbiome.
  • Yoghurt – here we’re referring to natural or Greek yoghurt. It’s actually quite easy to make your own but if you want to buy from the shop, your label reading skills will certainly come in hand.
  • Tempeh – this traditional soy product is also good for your gut health.
  • Miso – a traditional Japanese bean paste, miso can be used to make soup, added to salads or turned into a miso-mayo.

HINT: If you’re thinking about adding fermented foods, consume small portions daily. Use fermented food as a source of salt and as a replacement for your table salt and other sources of high sodium.

This image depicts a small batch of sourdough.
Naturally fermented sourdough is great! Image source: Ahead of Thyme

Examples of fermented drinks include:

  • Komboucha – a probiotic drink produced over a seven-to-ten day ferment and featuring SCOBY (symbiotic culture of bacteria and yeast).
  • Water Kefir and Milk Kefit – also with SCOBY (though known as grains) this drink is fermented over a period of two to three days. Milk kefir in particular has been named as one of the most potent out of all the ferments.

Negative foods for boosting your immune system

For optimal gut health, you’ll have to decrease your intake in foods that negatively influence your microbiome. Examples include:

  1. Excess red meat (linked to increased trimethylamine)
  2. Alcohol
  3. Saturated and trans fats
  4. Sugar
  5. Caffeine
  6. Processes foods
  7. Additives and emulsifiers
  8. Artificial sweeteners

Artificial sweeteners in particular pass through the stomach and intestines undigested so it directly encounters the bacteria there. Studies have shown that sweeteners can change the types of bacteria in your gut and increase bad bacteria twenty-fold while decreasing good bacteria ten-fold.


Vitamin C

Vitamin C is vital for your immune system and wellbeing. Being water-soluble, it’s the most easily destroyed of all the vitamins. It can be affected by oxygen or heat above 70 degrees.

The best way to ingest Vitamin C is directly from the source. Foods containing Vitamin C include:

  • Plums
  • Cherries
  • Capsicum
  • Guavas
  • Blackcurrants
  • Thyme
  • Parsley
  • Spinach
  • Kale
  • Kiwis
  • Broccoli
  • Brussels sprouts
  • Lemons
  • Lychees
  • Persimmons
  • Papayas
  • Strawberries
  • Oranges
This image depicts different types of citrus fruit containing healthy Vitamin C
Many citrus fruit contain Vitamin C. Image source: University of Washington

Vitamin D

Vitamin D–while not primarily sourced from food–is also very important for your body and health. It is produced from cholesterol when your skin is exposed to the sun. Hence, why it’s sometimes referred to as the ‘sunshine vitamin’.

Vitamin D is fat-soluble which allows it to be stored in your body for a long time. Even a small amount of sun exposure can offer positive benefits for a long time.

While known for its positive health effects for teeth and bones, a number of other benefits have also been discovered including improved immune function, and prevention of cancer and heart disease.

There aren’t a lot of good food sources for Vitamin D but you can get it from some produce.

  • Vitamin D3 – found in animal foods like fatty fish and egg yolks
  • Vitamin D2 – found in select plants, mushrooms and yeasts.

Of course, sunshine is the most effective way to get Vitamin D.

The importance of sunshine for your immune system

Did you know that 23% of Australians are deficient in Vitamin D?

Despite our glorious weather and strong Aussie sun, many of us fail to get the idea 10-30 minutes of midday sunlight exposure.

Of course, darker skinned individuals require more time than lighter skinned individuals to absorb the same amount of Vitamin D. Either way, when you’re getting much needed sunshine, make sure to expose your arms and legs as much as possible. Vitamin D is stored in the body for up to a few weeks or even months at a time, so just a little, occasional sunshine is enough to keep your levels adequate. If you live somewhere when you’re not able to get enough exposure to the sun (or during the winter months), using food and supplements to increase your intake in Vitamin D is essential.

Of course, it should go without saying that sun safe practices should be followed. Too little sun is bad for you, as is too much. Make sure to always Be SunSmart.


Zinc is a very powerful mineral and known as the ‘gatekeeper of the immune function’.

This mineral is often added to therapeutics such as nasal sprays, lozenges, and natural cold treatments. It is considered to be an essential nutrient because your body can’t produce or store it. Hence, it’s important you get a constant supply.

Food-based sources of zinc


The highest amounts of zinc, when it comes to food, can be found in animal products. Shellfish, meat, poultry, and fish are all excellent.


While plant-based food can be good to consume, generally the plant compounds inhibit absorption so less zinc can be absorbed efficiently.

Other foods

Some of the other foods with the best sources of zinc include:

  • Legumes
  • Nuts
  • Seeds
  • Dairy
  • Eggs
  • Wholegrains
  • Mushrooms
  • Kale
  • Peas
  • Asparagus
This image shows different types of shellfish, a good source of zinc for gut health.
Shellfish is a great source of zinc. Image source: iStock.

Additional Factors Affecting Immune Systems

Your diet, including food and drinks, are very important when it comes to your health and wellbeing, and the state of your microbiome. Sunshine, as we mentioned, is also very important. There are a few other additional factors worth concentrating on as well.


There has been a strong increase in the awareness of the benefits of enough quality sleep, thanks in part to things like the best-selling book “Why We Sleep” by Matthew Walker.

Making sure you get high quality, undisturbed, consistent and enough sleep is very important for your health and wellbeing. The full list of benefits is too extensive to list here but are certainly essential.


Life can be stressful. Stress and worry can be more than just emotionally and psychologically draining. It can also impact your body, immune system and gut health. Many people don’t realise how important it is to develop healthy daily schedules and habits that help you de-stress.


No surprises here. Physical activity and exercise is essential for maintaining a balanced, healthy life. Even just half an hour of walking a day can help you feel better, keep fit and improve your microbiome health.


There are many benefits to meditation outside from just pausing your day and slowing down a bin. From focusing on your breathing with high intensity, to appreciating life and even getting in touch with yourself and the present moment, meditation is an excellent habit for living a healthier, happier and more productive life


Are you suffering from NDD? Never even heard of NDD?

NDD stands for nature deficient disorder.

“Nature-deficit disorder” is not a medical diagnosis, but a useful term—a metaphor—to describe what many of us believe are the human costs of alienation from nature: diminished use of the senses, attention difficulties, higher rates of physical and emotional illnesses, a rising rate of myopia, child and adult obesity, Vitamin D deficiency, and other maladies.

Richard Louv, Greater Good Magazine

Spending more time in nature is beneficial not just physically but emotionally, psychologically and even at the level of your gut health and microbiome!

Image shows a forest nature setting with a sun shining through the trees.
Are you nature deficient? Image source: Edie

Conclusion: Quick tips for your immune system directly from our dietitian

Wow – that’s a lot of information! So, where to from here? Luckily for you, our very own dietitian has distilled the all of the advice from this article into three simple tips for boosting your immune system.

Tip 1

Aim for 30 different plant-based foods each week.

Tip 2

Enjoy and eat seasonal fruit and vegetables e.g. citrus in winter.

Tip 3

Focus on living a balanced, healthy and happy life.

Contact One Central Health Today

Have some more immune-system related questions? Give us a call today on (08) 9344 1318 to find out about our judgement-free dietitian services.

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