Coronavirus: Does 'boosting' your immune system really help fight off COVID-19?

With icky winter ills and chills rapidly approaching and a global pandemic on our doorstep, words like 'immunity', 'wellness' and 'probiotics' are inescapable - particularly during a lockdown which has social media stars bursting at the seams of their workout gear with excitement over pilates, ginger and lemon. 

But 'boosting' one's immunity - a concept that has no real scientific meaning - for increased protection against the virus is controversial. As self-proclaimed influencers peddle superfood products, it's important to remember that good gut health is essentially the key to what we call 'boosted immunity' - not trendy pills and potions.

As reported by the BBC, 'boosting' immunity is actually a misconception. Many symptoms we think are associated with illness are actually our body's immune response, such as gross amounts of snot and phlegm. For example, mucus can help flush out the pathogen and a fever helps to make the body an uncomfortably hot environment in which it's harder for the pathogen to replicate. These are signs the immune system is doing what it's supposed to do.

"The mucus and chemical signals are part of inflammation, which is the bedrock of a healthy immune response. But the process is exhausting, so you wouldn’t want to have it turned up to 11 all the time. And most viruses, including COVID-19, will trigger it anyway," Zaria Gorvett wrote for the BBC, based on an interview with Akiko Iwasaki, an immunologist at Yale University.

"If kombucha, green tea or any of the various 'immune-boosting' concoctions on the market really had any impact, they wouldn’t give you a healthful glow: they’d give you a runny nose. Ironically, many 'immunity-boosting' products claim to reduce inflammation."

In an interview with the Australian Academy of Science, University of Melbourne professor Peter Doherty, who shared the Nobel Prize for Medicine for his research on immunity, said a balanced, healthy diet is far more reliable than 'immune support' supplements.

"Some people believe in things like echinacea and so forth. My understanding is they haven't really checked out all that well when people have done proper trials. You'll never remove the possibility that some people genetically are set up to respond and some aren't. So, we don't know," he said.

"Maintain an adequate diet. If you're in a state of undernutrition, that's certainly a danger. And that's why people in very poor countries and so forth are at risk. We don't know how much being overweight is a risk factor for this virus. It was a big risk factor for the 2009 influenza pandemic. 

"We don't know of anything, despite all the claims in the pharmacies and drug stores and so forth that boost your immune system. We don't know whether any of those things have any validity at all, quite frankly."

In an article for New Zealand's Heart Foundation, national nutrition advisor Nicki Hursthouse reiterated that a strong immune system begins with a healthy microbiome, which consists of different strains of good bacteria living inside the gut. 

Hursthouse says the most effective way to increase good bacteria in the gut is by eating a variety of whole fruits and vegetables. Ginger, garlic and onion, as well as legumes and pulses such as beans and lentils, are all good bets. 

Fruit, vegetables and wholefoods are key to supporting a healthy gut, which in turn can strengthen immunity.
Fruit, vegetables and wholefoods are key to supporting a healthy gut, which in turn can strengthen immunity. Photo credit: Getty

Does strong immunity help you fight off COVID-19?

COVID-19 is caused by the SARS-CoV-2 virus. Just like any foreign bug, the body will defend itself against the invader. Strong immunity is built on a healthy gut microbiome and an army of white blood cells. If someone is consuming a healthy diet based on an array of fruits, vegetables and wholefoods (foods in their whole and unprocessed form - e.g. a potato instead of fries), the immune system should be better-equipped to fight off the virus - or any illness, according to the Heart Foundation.

Hence, maintaining healthy immune function cannot be achieved by scoffing chips, biscuits and packaged dinners every day, "balanced" by a probiotic, Berocca and lemon water. It's built through a healthy lifestyle. 

Vitamin C is widely touted for its immunity benefits, but if you're consuming enough fruit and veg, a supplement is unnecessary. Scientists in China are currently looking into whether ultra-high doses of vitamin C can help COVID-19 patients fight infection, but results will not be available until later this year.

In the meantime, the daily recommended intake can be achieved through citrus fruits, capsicum and greens such as broccoli and spinach. Unlike a pure vitamin C supplement, these foods also contain other vitamins and minerals that play an important part in keeping your immune system strong. 

There are also three tried and trusted methods to supporting your immune system - reducing stress, getting enough sleep and exercising regularly. 

What about all my supplements and never-ending supply of kombucha?

Kombucha tastes great, it's trendy and there are a number of options on the market that are relatively inexpensive. However, it's not a magic tonic - and drinking it by the litre is not going to ward off COVID-19. 

Like probiotics, kombucha contains live microorganisms. However, no studies have ever confirmed whether the drink has a high enough concentration to be considered a probiotic, and there is currently no evidence that kombucha can treat or prevent any illnesses

To strengthen one's gut health and immunity, a far more pragmatic bet is opting for probiotic foods such as plain, unsweetened yoghurt, which is full of live cultures, and fermented products such as kefir and sauerkraut. 

"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," Hursthouse wrote.

However, a vitamin D supplement can prove useful, particularly in parts of the world where sunshine is limited. Several studies have linked low vitamin D levels to a higher risk of respiratory infections. Vitamin D deficiencies are fairly common, and can be discovered through a blood test.

But again, if there isn't a deficiency, a supplement is not entirely necessary. As BBC Future reported in 2016, vitamin supplements typically don't provide any benefits in already healthy people.

And of course, prevention is always a good place to start. To minimise your chances of contracting COVID-19, follow the Ministry of Health's guidelines:

  • wash your hands frequently with soap and water for at least 20 seconds
  • cover your mouth with a tissue when coughing or sneezing and dispose of it
  • avoid touching your eyes, mouth and nose
  • clean and disinfect frequently touched surfaces and objects, such as doorknobs, desks, keyboards, mobiles and the kitchen and bathroom.