Boost your immune system to fight infection

Published: 2 April 2020

Never has there been more focus on the value of health and our immune system. Covid-19 (coronavirus) continues to spread globally and it is important to focus on what you can control to boost your immune system.

When a foreign bug gets into your body, like the one that causes COVID-19, your body puts up its defence. That defence is your immune system and the army you have inside your body are your white blood cells. You may not be able to prevent all risks of exposure to bugs like COVID-19 and guidance is provided by the Ministry of Health on how to prevent getting the disease. However, a healthy lifestyle can help build up your immune system to make your defence as strong as possible.

What foods boost my immune system?

Your immune system begins in your gut, all the different bacteria that live there are called the gut-microbiome. When your gut is healthy, it’s full of good bacteria which helps to strengthen your immune system. 

Fruit and vegetables in their whole form, rather than being juiced, are rich in fibre and help increase the good bacteria in the gut. Variety is also important so aim to eat a range of different coloured fruit and vegetables daily to boost your immune system.

Other immune system boosting foods that help keep your gut microbiome healthy include:

• Plain, unsweetened yoghurt
• Fermented foods such as kefir and sauerkraut
• Legumes and pulses such as beans, lentils and chickpeas
• Ginger, garlic and onion 

Vitamin C helps to build up the immune system.

Fruits and vegetables that are high in vitamin C include:

• Citrus fruits such as oranges, mandarins, lemons, limes and grapefruit
• Capsicum, especially the red capsicums
• Broccoli and spinach contain good levels of vitamin C as well as vitamin A and E

As with general heart-healthy eating, there is no one food or nutrient that is going to be the key to a strong immune system. All foods contain a variety of vitamins (i.e. vitamin C, E and A), minerals (i.e. iron, zinc, calcium and magnesium) and fibre that all play a role in keeping your immune system and body in good health. 

Keep your focus on a variety of whole, unprocessed foods to ensure that you are eating the right foods for your immune health.

Do I need to take lots of supplements to boost my immunity?

Supplements are a tablet form of common vitamins, minerals and other antioxidants that your body uses daily. Supplements are now readily available in supermarkets and health food stores, yet that doesn’t necessarily mean we need to be taking them daily.

Sometimes you might need to take a tablet form of a certain nutrient if you cannot get enough from food. However, usually you will get enough nutrients from the food you eat. You may have heard of the following supplements:

Vitamin C

Vitamin C is important as our body doesn’t store it and our bodies need it daily. We can get enough from our food when we are eating a variety of fruit and vegetables. This includes fresh, canned and frozen fruits and vegetables.

If you are eating lots of fruits and vegetables, it is best to avoid taking vitamin C supplements in bulk as you will be flushing your money down the drain.

Scientists in China have been looking to see whether ultrahigh doses of vitamin C can help COVID-19 patients both fight infection and reduce the symptoms of the disease. This is a large piece of work that is ongoing and there will be no results until later this year.

Vitamin D

Vitamin D is the ‘sunshine vitamin’, as we get most of it from the sun and it gives the body what it needs to produce vitamin D. Unless your vitamin D levels are low, usually shown by a blood test showing vitamin D deficiency, then a vitamin D supplement is not necessary.

While New Zealand sits at alert level 4, it’s important to get outside daily to move the body and for your headspace. Getting 15-20 minutes of sunshine on your face and forearms is also a great way to make sure your body is getting enough sunshine to maintain your vitamin D levels for now.

Probiotic supplements

Probiotic supplements are often taken to help boost the good gut bacteria mentioned above. The evidence is unconvincing right now as to whether you will get any extra benefit from a probiotic supplement over and above eating a healthy, well balanced diet.

‘Immune-boosting’ supplements

There is no evidence to suggest that supplements labelled as ‘immune-boosting’ such as green tea, zinc, elderberry or echinacea will provide any protection against COVID-19. It’s more important to have a healthy lifestyle overall.

Is changing what I eat enough to prevent COVID-19?

Taking steps to improve your lifestyle in a way that will strengthen your immune system doesn’t mean this will stop you from getting sick. However, it’s important to focus on what you do have control over during this time.

Focusing on healthy food choices to help your immune system is one area where you do have control, and this can help you to fight any infection that does make you sick.

The Ministry of Health guidance includes:

• Washing your hands often with soap and water for at least 20 seconds
• Using a tissue to cover your mouth when you cough or sneeze and dispose of immediately
• Avoid touching your face if your hands are not clean
• Clean and disinfect frequently touched surfaces and objects, such as doorknobs

As well as keeping yourself clean, give your home life a clean as well. Focus on cleaning the surfaces that you would touch frequently such as doorknobs, desks, keyboards, mobile phones, as well as your kitchen and bathroom.

Call Healthline on 0800 358 5453 if you have any symptoms or have been in close contact with someone confirmed with COVID-19.

Covid-19 information

Wellbeing tips for lockdown

Nickie Hursthouse, NZRD

National Nutrition Advisor

As a Registered Dietitian, I know that food gives us so much more than just nutrients. I am driven to simplify nutrition messages, educate on all aspects of food and support Kiwis to develop a love of food that helps them stay healthy throughout their life.

References:

• Carr AC, Maggini S. Vitamin C and Immune Function. Nutrients. 2017;9:1-15
• Martineau AR, Jolliffee DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356: i6583.
• National Institute for Health. US National Library of Medicine. Vitamin C Infusion for the Treatment for Severe 2019-nCoV Infected Pneumonia. https://clinicaltrials.gov/ct2/show/NCT04264533