The spike in Covid-19 cases 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. (…)
The supplement industry overall estimated value was around US$170 billion in 2020. 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 care 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 vaccination also effective against acute respiratory symptoms of Covid-19. Researchers also investigated whether 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-19. But there is little evidence supplementation in a healthy person prevents respiratory infections like Covid-19. A lack of evidence exist between a supplement’s action in laboratory or animal studies and the results of well-designed and conducted clinical trials.
A pandemic “infodemic”
Easy access to non-prescription supplements from a myriad of online and in-store sources and the uncontrolled spread of claims that supplements can prevent or treat symptoms of Covid-19, created a “infodemic”.
These claims are fueled by the fact that supplement manufacturers are able to “list” its products (here on the Australian Therapeutic Goods Register), with limited evidence of safety or effectiveness. This official endorsement appearance matches the common misperception that “natural” means “safe”.
Supplements can cause harm in the form of side effects, drug interactions and expenses. They also add to a patient medication burdencan delay more effective therapy or give false hope to vulnerable people.
Zinc Vitamins A
The recent COVID study from A to Z illustrates some of the challenges.
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 have been chosen because:
- studies of vitamin C in mice have shown that this antioxidant is essential for antiviral immune responses against influenza A virus, especially in the early stages of infection
- a 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.
In this large population-based observational study, they show a significant association between vitamin D deficiency and the risks of SARS-CoV-2 infection and severe disease in those infected. https://t.co/LJwzeBN6HL
— Caim (@CaimHaven) April 28, 2022
Little evidence of benefits
Despite the wide variety of complementary medicines marketed, most clinical trials to date have investigated the impact of vitamin D, vitamin C or zinc to reduce the risk of contracting Covid-19, improve hospitalization or death rates.
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 may be beneficial when individuals are unable to reach a balanced and varied diet.
High doses or chronic use of Covid-19 supplements have also been linked to side 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-19 or help you recover from infection, unless you have a known nutritional deficiency or a bad food. DM/ML
Treasure McGuire is the Deputy Director of Pharmacy, Mater Health SEQ in cross appointment as Associate Professor of Pharmacology, Bond University and Associate Professor (Clinical) at the University of Queensland.