Nutrition and Immunity

There is much interest in the media at the moment in boosting the immune system against COVID-19.  What does the evidence say? 

Firstly, it’s important to remember that no diet or supplement can prevent you catching a virus: you should always follow the Government guidelines about avoiding infection, and if you are ill, seek medical help as advised.  However, a healthy lifestyle can help to optimise immune function to deal with viral infection. 
A healthy lifestyle includes behaviours like getting adequate sleep and exercise, managing stress, limiting alcohol intake, and eating a healthy diet.

Whilst there are key nutrients necessary for the immune system to function, nutrition cannot ‘boost’ immunity – rather, good overall nutritional status helps it to function optimally. This is of particular importance as we age.  Good nutritional status is achieved by eating a wide range of healthy foods in a good balance, as shown in the Australian Dietary Guidelines.  It’s also important to minimise ultra-processed foods, high in refined carbohydrates, added sugars and fats, which can impair immune responses and promote excess weight.

What about supplements?

Be wary of marketing!  Taking additional vitamins and minerals is usually not necessary unless you have been diagnosed by your doctor with a deficiency, or you have particular dietary needs because of a specific condition, such as pregnancy or gut issues.  It is best to follow the advice of a health practitioner.  Also, the evidence shows that the health promoting effects of a healthy diet cannot be replaced by supplements – it’s the food that does you good!

If you want to ensure that you are getting adequate amounts of specific nutrients linked to immune system function, make sure that your diet includes some of food sources of these nutrients, listed below:

Vitamin A: oily fish, egg yolks, cheese, tofu, nuts, seeds, whole grains, legumes

Vitamin B6: whole grains, legumes, green leafy vegetables, fruit, nuts, fish, meat

Folate: green leafy vegetables, legumes, nuts and seeds

Vitamin C: citrus fruit, berries, kiwifruit, broccoli, tomatoes, capsicum

Vitamin D:  oily fish, eggs, some fortified foods

Vitamin E: nuts, green leafy vegetables, salmon, avocado

Iron: meat, legumes, whole grains, some nuts and seeds, leafy greens

Zinc: seafood, meat, legumes, nuts and seeds

Selenium: nuts, meat, whole grains, mushrooms

Remember to feed your gut bacteria too!

There is evidence that the gut microbiome is involved in regulating the immune system, so it’s important to have a diet rich in whole plant foods that will promote good gut health.  Every day include a range of high-fibre foods in your diet, like vegetables, fruit, whole grains, legumes, nuts and seeds.

What about fasting?

While the current evidence is that short-term fasting may reduce inflammation, it is not necessarily associated with an increased immune response to infection.  Fasting should only be undertaken with professional guidance to ensure that it is safe for you, and that you do not lack essential nutrients.

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