Building a healthy immune system


By Sherrie Miller

At this time of year, the weather gets colder and we become more susceptible to all sorts of nasty bugs and viruses.  Many people believe that the flu shot is essential for winter, and whilst it may be a good option for the vulnerable, the flu shot doesn’t protect you from every strain of flu out there.  Building a strong immune system through proper nutrition is a better option.

Don’t underestimate the power food and nutrition play in building immunity.  Nutrition is paramount in building a strong immune system, not only to help prevent catching nasty viruses, but if you do happen to catch something, a strong immune system will help you fight the bug and get you back on your feet much quicker.  Key nutrients in building a strong immune system includes Zinc, Vitamin A, C and D, and of course eating a diet rich in whole foods that includes plenty of plant foods, are essential.

Zinc-Rich Foods

Zinc is a key mineral in building a strong immune system.  It is required to make and activate T-cells – our disease-fighting cells.  Oysters are the richest source of zinc.  Other food sources of zinc include crab, lobster and prawns, beef, sesame seeds, pumpkin seeds, cashews, chickpeas and quinoa.

Citrus Fruits

Citrus fruits that include lemons, oranges, grapefruit and limes are high in Vitamin C.  Vitamin C is crucial for fighting off infections.  Notice how citrus fruits are always in season during the colder months?  Mother Nature knows when we need extra Vitamin C!


Pineapple is also a rich source of Vitamin C, but pineapple also contains a protein-digesting enzyme called Bromelain.  Bromelain is found in the core of the pineapple.  Bromelain has anti-inflammatory properties, acts as a cough suppressant, assists the body in expelling mucous and fresh pineapple juice also helps sooth a sore throat.

Vitamin A Foods

Vitamin A, also known as Retinol, is from animal products and found in liver, dairy products such as cheese and butter and also found in eggs.  Cod Liver Oil is an excellent source of Vitamin A.

Provitamin A which is mostly found in beta-carotene foods, is converted to Vitamin A once consumed.  Provitamin A foods include red, orange and yellow fruit and vegetables such as sweet potatoes, carrots, bell peppers, cantaloupes, tomatoes and peaches.  It’s also found in green leafy vegetables.  Vitamin A strengthens cells and mucosal linings within the human body acting as a barrier to potential pathogens.

Vitamin D

More and more research is discovering how crucial Vitamin D is for many biochemical functions within the human body and this includes strengthening and modulating our immune system. Globally we are becoming very Vitamin D deficient due to modern day living and working, and of course in winter, we spend even less time out in the sun causing further Vitamin D deficiency.  It is worth talking to your doctor about getting a Vitamin D blood test to see where your levels are at.  Vitamin D deficiency can be hard to detect but can include low immunity – getting sick many times throughout the year, sore and/or soft bones, mental health issues, chronic pain, psoriasis, and insomnia.  The sun is most definitely the best source of Vitamin D and it’s recommended to get 15 – 30 minutes of unprotected sun exposure a day for optimum Vitamin D levels.

Food sources include cod liver oil, fish, eggs, mushrooms grown in sunlight, and butter.  Vitamin D fortified foods usually contain the wrong source of synthetic Vitamin D that the body cannot absorb and utilise, so best to avoid.  Over the winter months or if blood test results indicate very low levels of Vitamin D, consider taking a good quality Vitamin D3 supplement to up the levels.

Ginger and Turmeric

These root spices are anti-inflammatory kings!  Ginger has antibacterial, antiviral, antioxidant, and anti-parasitic properties.  Turmeric is fast becoming the most researched spice, due to the compound Curcumin and its powerful anti-inflammatory and antioxidant properties, and its use in disease prevention.  With both of the spices’ warming properties, it’s the perfect anecdote to warm your body from the inside out during the colder months as it fights inflammation.


Approximately 70% of our immune system sits around our gut and therefore a healthy, functioning gut is essential for a healthy functioning immune system.  Processed foods, refined sugar, chemicals, toxins, medication and stress all impact the health of our gut.  Lack of good bacteria in our gut influences many aspects of our health.   When we lack the good bacteria in our gut it can cause inflammation of the intestinal wall, affect proper nutrient absorption and overall gut function.  A good probiotic supplement or adding fermented foods to your daily diet, can assist in getting the right balance of good gut bacteria.  The study of our gut bugs is an exciting area of medicine at the moment, and research is finding so many fascinating things about our gut bacteria, and this includes certain species that assist in strengthening and maintaining our immune system by way of proper nutrient absorption, work together like an army to push out bad pathogens, fight inflammation and strengthen the gut wall.  Prebiotics are also important to feed and keep the good gut bugs happy!  Ensure your diet is rich in prebiotic fibre foods too.

Gelatin and Bone Broth

One of the best remedies for gut healing is bone broth.  The key healing ingredient in bone broth is gelatin.  Long term inflammation to our gut lining causes ‘holes’ to appear in the intestinal lining (leaky gut) allowing toxins, food particles and bacteria to enter the blood stream.  This has a huge impact on our immune system.  The gelatin in bone broth helps to repair the lining of the gut wall to then allow the immune system to function at its best.  You can also add unflavoured grass fed gelatin powder to things like smoothies or soups to assist with gut healing.

Avoid Sugar

A diet high in refined sugar and highly processed grains suppresses the immune system not allowing it to function at its best, leaving you more likely to catch something.  Sugar also feeds the bad bacteria that may have caused your head cold or flu, so to recover quicker, avoid sugar all together when sick.

Ultimately, eating a diet rich in quality whole foods is the best way to build a strong and healthy immune system, and prevent potential chronic dis-ease in the future.

Sherrie Miller is a qualified Nutritionist with a special interest in gut health. She is passionate about the way in which our digestive health can influence our mental health, skin health and immunity.  Sherrie takes the concept of ‘Food is Medicine’ very seriously. 

You can find out more on instagram @sherriemillernutrition


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