Building Immunity to Protect Against Coronavirus - Shelley Cavezza, PhD

Building Immunity to Protect Against Coronavirus

You can reduce your susceptibility to respiratory viruses such as the Coronavirus by strengthening your immune system. A competent immune system can reduce the risk of infection as well as reduce the severity of symptoms and speed up the recovery process. 

A healthy diet providing key nutrients is essential to a strong immune system; and don’t wait until you have viral symptoms to protect yourself.  At the first sign of infection taking specific vitamins can help reduce symptoms.

The body can fight viruses

The immune system is made up of a network of chemical messengers, cells, tissues, and organs that work together to protect the body. Fuelling the body with virus fighting substances helps this network do its job.

What to do if you contract the virus

Large doses of vitamin C at the first sign of a cold have been shown to reduce the severity and duration of the symptoms (1). This is because viruses kill off white blood cells quickly at the onset of a cold, and vitamin C supports cellular defence mechanisms. Zinc has also been shown to inhibit the survival of the virus in the body.

What can you do to build a strong immune system to fight viral infections?

A healthy diet with adequate consumption of vitamins, minerals and antioxidants are essential for optimal immune function (2). Fruits and vegetables such as citrus fruits, berries, kiwi fruit, capsicums, broccoli and spinach are great sources of vitamin C, vitamin E, and antioxidants. Garlic, ginger, dark chocolate and green tea contain natural antioxidants, and shellfish and seeds are high in zinc.  All are shown to support a healthy immune system.

Studies have supported the protective qualities of foods. For example, fresh garlic extract was shown to kill human rhinovirus in laboratory studies (3). In a double-blind trial, administration of a garlic extract reduced the incidence of the common cold.


Vitamin C

Vitamin C concentrations in immune white blood cell have been found to fall quickly within 24 hours of the onset of a cold. This decline is possibly due to increased vitamin C utilization for cellular defence . Clinical trials that used relatively large doses of vitamin C (usually 1–8 g/day for adults) found that treatment with vitamin C at the first sign of a cold reduced the duration of illness or the severity of symptoms in most people.


Zinc ions have also been shown to inhibit the survival of rhinovirus in laboratory studies.  In several clinical trials, treatment with zinc lozenges significantly reduced the duration of cold symptoms in adults. Foods that contain zinc include shellfish such as oysters, crab, and mussels and seeds such as pumpkin and sunflower, with the daily recommended amount (11mg for men and 8mg for women).

Vitamin D

Vitamin D plays a role in immune function with increasing evidence of health problems associated with vitamin D insufficiency. The higher incidence of colds during the winter might be due in part to relatively low vitamin D status during the winter months. Vitamin D supplementation seems to be most effective in children, and in adults with frequent respiratory infections or low baseline vitamin D status.

Vitamin A

Vitamin A plays a role in immune function by enhancing the structural integrity of the respiratory mucosa. In a double-blind trial, vitamin A supplementation reduced the incidence of respiratory infections in preschool children.

Vitamin E.

In a double-blind trial, vitamin E supplementation reduced the incidence of the common cold by 20% in elderly nursing home residents. Foods with high vitamin E include avocados, dark leafy greens and nuts.


Numerous double-blind clinical trials have found that administration of specific probiotic organisms such Lactobacillus rhamnosus GG decreased the incidence or duration of respiratory tract infections in children, preterm infants, and adults although not all trials were positive.

N-Acetylcysteine (NAC)

NAC is a precursor to the master antioxidant glutathione. In a double-blind clinical trial, administration of NAC during the flu season reduced the frequency and severity of symptomatic influenza episodes.

What else can you do?

Coronaviruses and rhinoviruses can be transmitted from person to person, usually after close contact with an infected person, for example, in a household or workplace. The World Health Organisation (WHO) recommendation to prevent infection includes regular hand washing and covering mouth and nose when coughing and sneezing. Conventional treatment for respiratory viruses, such as decongestants, and nonsteroidal anti-inflammatory drugs may decrease symptoms, but they do not shorten the duration of the cold and won’t prevent infection.

A healthy immune system will fight the virus in its infancy before symptoms have a chance to develop. Of course, that is the best option against this new strain of virus.

Functional medicine specialists can help educate people on which foods and supplements they can take to reduce their risk of infection. Educating yourself on the effects of vitamins and dosage can take out the guesswork. For example, Vitamin C does not store in your body, and if a person takes too much, it can cause diarrhoea. Other vitamins can store in the body and taking too much can cause complications.

For the best results, people should complement a good diet with regular moderate intensity exercise.  If sick, then rest and recovery is recommended.

Dr Cavezza operates a Functional Medicine Nutrition clinic on the Sunshine Coast and has been an Immunology Researcher for 25 years. For more information join Dr Cavezza on Facebook: Dr Shelley Cavezza or Instagram: @dr_shelley_cavezza or webpage:


  1. Ran L, Zhao W, et al. Extra Dose of Vitamin C Based on a Daily Supplementation Shortens the Common Cold: A Meta-Analysis of 9 Randomized Controlled Trials. 2018 Biomed Res Int:1837634. doi: 10.1155/2018/1837634.
  2. Maggini S, Pierre A, Calder PC. Immune Function and Micronutrient Requirements Change over the Life Course. 2018 Nutrients: 10(10). doi: 10.3390/nu10101531.
  3. Arreola R, Quintero-Fabián S, et al. Immunomodulation and anti-inflammatory effects of garlic compounds. 2015. J Immunol Res: 401630. doi: 10.1155/2015/401630.