Myth: dietary supplements prevent coronavirus (COVID-19)

Tamara Willner
Written by

Tamara Willner

12th May 2020

With the coronavirus (COVID-19) outbreak, many of us are experiencing higher levels of stress or anxiety. It’s important to think about how we can best support our immune system, but unfortunately, there’s a lot of misinformation online.

Contrary to popular belief, diet and nutrition supplements won’t prevent coronavirus. Eating a balanced and varied diet is important for optimising our immunity and keeping our bodies strong and healthy.

The only confirmed way to reduce our risk of contracting coronavirus is to follow government and public health guidance on hand hygiene and social distancing.

Many of the current myths circulating the media draw conclusions from studies, which are usually weak, investigating the effect of certain supplements or foods on colds and the flu. However, coronavirus is a new and completely different virus, which means we can’t translate findings from other viruses or infections to coronavirus.

This guide reviews some of the most common nutrition myths relating to COVID-19 to see whether or not they’re supported by strong scientific evidence.


Echinacea is a herb that’s commonly found in herbal teas or supplements.

Although it’s popular and touted as a powerful immune booster by natural health practitioners, there’s little evidence for its role in immune health. In fact, one randomised controlled trial (RCT) of 713 people found no difference in the severity or duration of the common cold in people taking echinacea pills compared with those taking placebo pills or no pill at all.

Furthermore, there’s no evidence that echinacea can treat or prevent coronavirus, which is a new and different virus to the common cold.

Key points:

  • Echinacea is a popular herb found in teas and supplements
  • However, high-quality evidence suggests it has no effect on common cold symptoms. There’s no evidence it can treat or prevent coronavirus either.

Lemon juice

As with many other foods, lemons contain vitamin C, which helps with immunity.

According to a rumour circulating online, lemon juice can ‘kill’ coronavirus and prevent it from spreading. However, there’s absolutely no evidence to support this.

Those who support this myth suggest that lemons change the pH of our bodies, creating an acidic environment in which the virus can’t survive. This uses the same flawed logic as the popular alkaline diet, that we’re able to change the pH of our bodies through diet. This isn’t possible unless you have an underlying medical condition.

Plus, different parts of our bodies naturally have different pH levels. For example, the stomach has a low pH (2-3) typically due to the presence of stomach acid, which breaks down food for digestion. Lemon juice has a similar pH to this, so even if there was any truth to this myth, our stomachs would be doing a good enough job of ‘killing’ anything harmful we ingest.

Our bodies have complex systems in place to regulate the pH levels of our blood. For example, the kidneys. Drinking lemon juice will have no effect on the pH level of your body.

Key points:

  • Some people claim that drinking lemon juice can increase the acidity of our bodies, ‘killing’ the virus
  • Different body parts have different pH levels and it’s a tightly regulated system, unaffected by our diet.

Black or green tea

It’s been claimed that the compounds in tea, such as methylxanthines, can destroy the coronavirus.

However, there’s no evidence to support this, and the doctor who made this claim actually specialised in eye health, not infectious disease.

Weak evidence from a test tube study suggested that a compound in black tea could inhibit the virus that causes severe acute respiratory syndrome (SARS). However, this study has several limitations.

Firstly, the dose used in this study was far higher than the amount we’re typically exposed to through drinking tea. Secondly, we can’t translate findings from test-tube studies to human health or make conclusions until human trials are conducted. Finally, coronavirus isn’t the same virus as SARS, so the results from this study don’t apply to coronavirus.

Some evidence — including high-quality RCTs — suggests that certain compounds in tea, called catechins, may help protect against seasonal flu and the common cold, potentially by reducing the virus’s ability to bind to receptors in our body and/or replicate itself. But again, we can’t apply these findings to coronavirus, as it’s a new disease that may respond differently.

There are some health benefits to drinking tea. For instance, the plant compounds (polyphenols) found in black tea may marginally help to reduce blood pressure. In a 6-month RCT of 95 people, those who drank 3 cups of polyphenol-rich black tea daily had small improvements in blood pressure compared to those who didn’t. However, tea itself won’t protect us from coronavirus.

Key points:

  • Some social media claims suggest that drinking tea can protect us from coronavirus, but there’s no evidence to support this
  • Tea may have some unrelated health benefits, but more high-quality studies are needed.


There are mixed rumours circulating about the effects of elderberry on coronavirus.

Some natural health practitioners have suggested that elderberries can worsen coronavirus symptoms by triggering a ‘cytokine storm’, which sends the immune response into overdrive and adds strain. Others have claimed that elderberry supplements can help prevent and treat the virus (along with seasonal flu).

There’s no evidence to support either of these claims. What’s more, the claims about seasonal flu aren’t supported by strong evidence. One small meta-analysis of RCTs, with only 180 participants in total, suggests that high-dose elderberry supplements may reduce the symptoms of viral upper respiratory infections. But larger and higher-quality trials assessing the effects of elderberry on viral infections are needed.

Key points:

  • There’s no evidence to support the claims that elderberry worsens or protects against coronavirus
  • One small meta-analysis suggests that elderberries may reduce viral symptoms, but more high-quality research is needed.


Without a doubt, garlic (along with other fruits and vegetables) is a healthy food to include in our diets.

Although there’s no evidence to support the use of garlic for coronavirus, it may help improve overall immune health due to its allicin content. Allicin gives garlic its strong odour and flavour and has many health benefits.

Eating about one clove of garlic per day — which is easy to do by simply using it in cooking — may strengthen our immune systems, lessen the severity of our symptoms when we do get sick, and help us to recover more quickly from general illness. However, this doesn’t tell us anything about the relationship between coronavirus and garlic.

There’s a number of different ways to eat more garlic. Fresh garlic contains the most allicin, closely followed by dried garlic. Aged garlic and black (fermented) garlic contain less allicin, but still have some immune benefits.

One study found that garlic oil contains no allicin. On top of this, garlic oil has a potentially high level of toxicity and it’s easy to overconsume, as most supplements contain large amounts. So it makes sense to stick to using fresh, dried, or aged (fermented) garlic in your cooking.

Key points:

  • Including garlic in our food may be beneficial for generally strengthening our immunity due to its allicin content
  • It’s best to eat garlic in fresh form, by using it in cooking.

Drinkable Silver

The use of colloidal silver (tiny particles of silver suspended in liquid) has been rumoured to treat coronavirus and boost immunity.

There’s no evidence to support these rumours – in fact, the person circulating this rumour admitted it hadn’t been tested on coronavirus.

Government organisations say that colloidal silver isn’t a safe or effective treatment for any diseases or conditions. It could even cause serious, dangerous side effects such as kidney damage and even seizures.

Key points:

  • There’s no evidence to suggest that drinkable (colloidal) silver treats coronavirus and boosts immunity
  • It isn’t a safe or effective treatment for any diseases or conditions — in fact, it could have harmful side effects.


There’s no evidence that probiotics can treat or prevent coronavirus. However, probiotics may promote a healthy gut and there does appear to be a link between gut health and general immunity.

One small RCT of 152 volunteers found that the probiotic strain Bifidobacterium animalis had promising effects on common colds compared with a placebo, but there’s no evidence it would have the same effect on coronavirus.

It’s important to note that not all probiotic strains are equally effective for all diseases or symptoms and there are billions of different strains. Therefore, it’s near impossible to make specific recommendations until further research is conducted.

We can optimise our gut health using a food-first approach. Try to include a mix of probiotic-containing foods in your diet — such as kimchi, sauerkraut, yoghurt, kefir, or natto.

Prebiotic foods should also feature regularly in your diet. Prebiotics act as a fertiliser for good bacteria (probiotics) in our guts, promoting their growth. Eating a variety of vegetables such as beetroot, onions, garlic, and leeks will help to grow and populate the healthy bacteria in your gut.

Key points:

  • Probiotics may improve gut health, which is linked to generally improved immunity, but further research is required
  • There’s no evidence that probiotics can prevent or treat coronavirus
  • Try to include some probiotic-containing and prebiotic foods in your diet to naturally optimise gut health.


There’s no evidence that multivitamins, in particular, can prevent coronavirus. One RCT of 477 people did find that a combination of probiotics and a multivitamin helped reduce the incidence and severity of viral colds by 13.6%.

However, this study doesn’t tell us whether the probiotics or the multivitamin made the difference. Additionally, whilst the study participants were classified as ‘healthy’, there were many other factors that could have impacted the results. These include the participants’ diet before the trial, alcohol intake, or exercise levels, as these factors weren’t controlled for. Being deficient in any vitamin or nutrient would put strain on our immune system, and so a multivitamin correcting any deficiencies would likely show a positive result.

On top of this, although this combination may have helped with the common cold or flu, we can’t translate these results specifically to coronavirus as it’s a new, different virus.

For healthy individuals, it’s important to eat a balanced diet including a variety of vegetables and whole foods to ensure we don’t have any deficiencies. If you’re limited in what you can eat then a multivitamin might help to provide extra vitamins you can’t get from your diet, but you should consult a medical professional first.

Key points:

  • Multivitamins aren’t proven to protect against coronavirus
  • We can’t translate findings around cold and flu to coronavirus as it’s a new, different virus
  • Most people can get all the vitamins required from a healthy and balanced diet.

Take home message

  • The best way to protect yourself against coronavirus is by following the latest government and public health advice around hand hygiene and social distancing.
  • Eating a healthy, balanced diet, getting adequate sleep, and staying hydrated will help to keep your immune system strong.
  • For the most part, there’s no need to take supplements — we can get everything we need through diet.
  • Probiotics and garlic and their effects on immunity are exciting areas of research, but more studies are needed.
  • Including garlic and probiotic-containing foods in the diet may provide some immune benefits, but no research suggests that these are specific to coronavirus.
  • If a claim sounds too good to be true, it probably is. Ask for evidence and always question who is giving the advice.
  • Address any concerns about supplements with a medical professional.
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Write a response

Carol Gray

19 May, 2020

This is an excellent article. It is nicely laid out and highlights the key points. So much rubbish is bandied around that you need something informative such as this article to tell it like it is

Pamela Watson

18 May, 2020

Thanks for that it was very interesting.

Stephen Trevor

18 May, 2020

I was inform long ago that echaniacea May affect hiv medication not sure if that true though but I’ve always avoided it.

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