The spike in COVID-19 cases in Australia this year has seen many people seek ways to protect themselves or boost their immunity and recovery.

A recovery in the sales of dietary supplements followed.

In Australia, the Therapeutic Goods Administration groups vitamins, minerals, amino acids, enzymes, herbal extracts and microbiome supplements under the term “complementary medicine”.

The estimated global value of the supplements industry was around US$170 billion ($239 billion) in 2020.

Australian revenue from complementary medicines was estimated at $5.69 billion in 2021, which has doubled over the past decade.

The latest data shows that 73% of Australians purchased complementary medicines in the previous year, with vitamins featuring in more than half of purchases.

But how likely are these purchases to be effective in preventing or treating COVID-19?

Fear, avoidance and laboratory studies

Historically, the public has purchased supplements from sources that also provide health advice.

Lockdowns and general health messages about social distancing and personal hygiene have created a new normal.

So, people are shopping more online for supplements and are turning to the internet, friends, or social media for vitamin recommendations.

For some, this has led to an unhealthy fear of COVID (coronaphobia) and negative impacts on daily life.

As with any medication, consumers should seek information from reputable sources (doctors, pharmacists, or peer-reviewed evidence-based articles) about the benefits and potential harms of supplements before purchasing them.

Strong evidence supports that vaccination is effective against acute respiratory symptoms of COVID.

The researchers also looked at whether the supplements could prevent or reduce the duration and severity of this viral infection by boosting the immune response.

Deficiencies in essential nutrients that support immune function (vitamin C, vitamin D, zinc, and selenium) have been shown to increase susceptibility to infections, including COVID.

But there is little evidence that supplementation in a healthy person prevents respiratory infections such as COVID.

There is an evidence gap between a supplement’s action in laboratory or animal studies and the results of well-designed and conducted clinical trials.

A pandemic “infodemic”

The easy access to non-prescription supplements from a myriad of online and in-store sources, and the unchecked spread of claims that supplements can prevent or treat COVID symptoms, have created an “infodemic.”

These claims are fueled by the fact that supplement manufacturers can “list” their products on the Australian Therapeutic Goods Register, with limited evidence of safety or effectiveness.

This appearance of official endorsement matches the common misperception that “natural” means “safe.”

Supplements can cause harm in the form of side effects, drug interactions, and expense. They also increase the patient’s drug burden, can delay more effective treatment or give false hope to vulnerable people.

Zinc Vitamins A

The recent COVID A to Z study illustrates some of the challenges involved.

It was designed to test the effectiveness of high-dose zinc, vitamin C, and a combination of the two, in shortening the duration of COVID-related symptoms compared to usual care in adult outpatients with confirmed infection. .

These nutrients were chosen because:

• Studies of vitamin C in mice have shown this antioxidant to be essential for antiviral immune responses against influenza A virus, particularly in the early stages of infection.
• Deficiency in zinc, an essential trace mineral, has been associated with increased susceptibility to viral infections.

The authors planned to include 520 patients, but the safety monitoring committee recommended premature termination of the study, due to the low probability of detecting significant differences in results between the groups.

There were also more adverse effects (nausea, diarrhea, and stomach cramps) reported in the supplement groups than those receiving usual care.

Tweet from @CaimHaven

Little evidence of benefits

Despite the wide variety of complementary drugs on the market, most clinical trials to date have investigated the impact of vitamin D, vitamin C or zinc in reducing the risk of contracting COVID-19, improving levels of hospitalization or death.

Even with high treatment doses, the results were generally disappointing.

Vitamin D, zinc and some probiotics may be beneficial to to prevent viral infections.

Vitamins D, C, A, zinc, calcium and some probiotics may be beneficial to treat viral infections. But other studied supplements (including copper, magnesium, selenium and echinacea) are unlikely to be beneficial or are not supported by sufficient data.

However, supplements can be beneficial when individuals are unable to eat a balanced and varied diet.

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Potentially dangerous

High doses or chronic use of COVID supplements have also been associated with adverse effects: Vitamin D with muscle pain and loss of bone mass; vitamin A with elevated liver function tests and blurred vision; vitamin E with hemorrhagic risk; plant extracts, magnesium with gastrointestinal effects; and selenium with hair loss and brittle nails.

Thus, the evidence is not convincing that taking vitamins and supplements will prevent you from catching COVID or help you recover from infection, unless you have a known nutritional deficiency or poor diet.

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Treasure McGuire, Deputy Director of Pharmacy, Mater Health SEQ in Joint Appointment as Associate Professor of Pharmacology, Bond University and Associate Professor (Clinical), University of Queensland

This article is republished from The Conversation under a Creative Commons license.