Food as medicine against COVID-19? – Dr. Catherine Norton

Dr Oz has been all over US network television recently advising on strategies to avoid contracting, but also on how to treat the corona virus! The TV host’s ‘survival guide’ covers such diverse topics on protecting yourself as meditating, to stockpiling toilet roll. The nutrition aspect of his advice claims benefits of vitamin D supplementation and eating fruit and veg to protect yourself and consuming elderberry syrup four times a day for 5 days to treat the viral infection. If only it were that simple! Thankfully, Dr Oz is not heading up our national response to containing the corona virus in Ireland. In the words of Jürgen Klopp, ‘People with knowledge will talk about it. I wear a base[ball] cap and have a bad shave. My opinion [on corona virus] is really not important.”

Is there any truth at all in the claims from Dr Oz? The former Oprah Winfrey protégé has a history of doling out scientifically dubious claims so let’s see if there is anything worth taking from his survival guide.

Washing your hands, maintaining social distancing, avoiding touching your mouth or nose, appropriate cough and sneeze etiquette as well as practicing good food hygiene are all accepted as sound advice with good evidence in support of these recommendations. The WHO also advise on adopting good sleep, activity and dietary practices if you feel stressed during the outbreak. They do not advocate for elderberry syrup however. It is implicit in the WHO advice that optimal lifestyle practices (sleep, activity and diet) can support health and may prevent ill health. However, the bottom line is that there is no magic pill or a specific food guaranteed to bolster your immune system and protect you from the new coronavirus.

Nevertheless, there are real ways you can take care of yourself and give your immune system the best chance to do its job against any respiratory illness.  A healthful diet is important to maintain a functioning immune system. However, no single food or natural remedy has been proven to ward off disease. For many years, high dose Vitamin C consumption has been part of cultural practice when suffering with a cold or flu’.  This is due to a book published by Nobel prize winner Linus Pauling (circa 1970) theorising on how vitamin C helps treat colds. In the following few decades, multiple randomized controlled studies examined whether the vitamin had any effect on the common cold. The results have been disappointing. An analysis of 29 studies including 11,306 participants concluded that supplementing with 200 mg or more of vitamin C did not reduce the risk of catching a cold. However, regular vitamin C supplements had several benefits, including:

  • Reduced cold severity: They reduced the symptoms of a cold, making it less severe.
  • Reduced cold duration: Supplements decreased recovery time by 8% in adults and 14% in children, on average.

A supplemental dose of 1–2 grams was enough to shorten the duration of a cold by 18% in children, on average.

Zinc supplements and lozenges are another popular remedy for fighting off colds and respiratory illness. Some studies have found that zinc lozenges may reduce the duration of cold by about a day and, may reduce the number of upper respiratory infections in children. However, the data on zinc are mixed.

The data on vitamin D and immune function is also equivocal. Vitamin D (often referred to as the sunshine vitamin) is found in fatty fish, such as salmon, and in milk or foods fortified with vitamin D.  A more recent analysis of 25 randomized controlled trials of 11,000 patients showed an overall protective effect of vitamin D supplementation against acute respiratory tract infections. The research is not conclusive, and some studies of vitamin D have not shown a benefit.

It has long been know that an individual’s nutritional status can influence their susceptibility to and their response to infection. Adherence to general healthy eating guidelines, and consuming adequate fluids seems like the best advice for now.  The last word should go to the founder of the concept of food as medicine; Hippocrates: “If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health.”

Dr Catherine Norton is a performance nutritionist and registered dietitian.  Dr Norton works at the University of Limerick and teaches on the BSc Sport & Exercise Sciences and MSc Sports Performance courses as well as researching in both food for health and performance nutrition.  Contact Catherine via email on or follow Catherine on @NortonNutrition

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