A deficiency of micronutrients, including zinc, selenium and vitamins A, D and E, has been shown to be harmful in viral infections. Meanwhile, multivitamin supplementation, for example, has been shown to reduce the risk of respiratory infection.

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So, can dietary supplements and herbal “drugs” help improve coronavirus disease 2019 (COVID-19)? If so, they present a potentially practical and accessible method for recovering from the global pandemic.

Vitamins C, D and zinc are known to benefit immune function, including reducing the risk of respiratory infection. Other dietary supplements such as omega-3 fatty acids (“fish oil”), probiotics, and plant isolates like garlic are also considered important.

The use of health supplements for the treatment of COVID-19 has been advocated by some celebrities – medical entertainment figures – both on television and via social media. Therefore, in the UK for example, there has been an increase in sales of health supplements such as vitamin C and zinc.

How could health supplements help in the COVID-19 pandemic?

Vitamin D

The antimicrobial role of vitamin D in infectious diseases has been known for about a century. In the wake of the pandemic, interest in this vitamin and its role in reducing the risk of acute respiratory symptoms has sparked increased interest.

Immune cells express the vitamin D receptor, and some cells can synthesize vitamin D in its active form. Vitamin D influences antigen presenting cells, T cells and B cells.

In terms of COVID-19, an overlap between certain risk factors for vitamin D deficiency (age, obesity and ethnicity) and the severity of the infection has been found. In cases of COVID-19, vitamin D is thought to reduce viral transmission by boosting antiviral immunity and decreasing the cytokine storm associated with severe cases of infection.

Zinc

Zinc is well known to support immune function and is believed to have specific antiviral effects.

Vitamin C

Like zinc, vitamin C has been shown to support the immune system and possibly prevent respiratory infections.

omega-3 fatty acids

Like vitamin D, omega-3s are thought to influence antigen-presenting cells, T cells, and B cells. More consistent research has shown that they have an anti-inflammatory effect.

Multivitamin

Supplements generally include several vitamins, minerals and trace elements. These have antioxidant properties and are therefore believed to play an important role in supporting the immune system.

Probiotics

Probiotics interact with the intestinal microflora and can generate antiviral metabolites influencing the immune system.

Current research on health supplementation and COVID-19

There is a lack of evidence specifically supporting a role of health supplements in reducing symptoms of COVID-19. A group of researchers sought to address the knowledge gap by investigating a large sample of participants who were using the COVID-19 symptom study app.

In a large observational study involving 400,000 users, Louca et al. (2021) found a significant association between taking health supplements and a reduced risk of testing positive for the virus.

Researchers focused on multivitamin or vitamin D supplements, omega-3 fatty acids, and probiotics. Surprisingly enough, the positive effects occurred among participants based in the UK, US and Sweden. The explanation for these findings was as follows:

1. Biology –– sex discordant immune systems

Previous research has shown an increased immune response in women with respect to nutritional metabolism and it has been found that women have a more resilient immune system more generally.

2. Body mass and composition –– differences between the sexes have implications for dosage.
3. Gender differences in health-related behaviors – Women have been shown to display more cautious behaviors in association with concerns for themselves and their families.

Researchers found that there was no protective effect from dietary supplementation with zinc, garlic or vitamin C.

In another study published in late summer 2021, researchers investigated the use of dietary supplements and herbal remedies in patients with COVID-19. In a systematic review of randomized clinical trials, involving interventions with dietary supplements or the use of herbal medicines in England and China, researchers found that herbs may be helpful in relieving symptoms of COVID- 19.

The use of herbs is considered a form of dietary supplement in the western world, while in China, herbs are consumed for medicinal purposes.

The use of zinc sulfate sparked the interest of researchers during the pandemic. Loss of taste and smell was one of the first reported symptoms of COVID-19 infection. Unlike Louca et al., (2021) Feng et al. found that zinc supplementation was beneficial in cases of COVID-19. Here it was believed to shorten the duration of olfactory dysfunction.

In conclusion, so far little research has been done and the results have been inconsistent. Diet therapies are proving to be incredibly difficult to study and there is a lack of high quality evidence.

Available studies should be considered in the context of an urgent epidemic rather than as part of any systematic and well-planned treatment regimen. Despite the limitations, dietary supplements and herbal medicines are believed to present an effective adjunct therapy for patients with COVID-19.

The references:

• Feng, Z et al. 2021. Dietary supplements and herbal medicine for COVID-19: a systematic review of randomized controlled trials. ESPEN Clinical Nutrition. do I. 10.1016 / j.clnesp.2021.05.018.
• Louca, P. 2021. Modest Effects of Dietary Supplements During the COVID-19 Pandemic: Information from 445,850 Users of the COVID-19 Symptom Study App. BMJ. doi: 10.1136 / bmjnph-2021-000250.
• Torjesen, I. 2020. Covid-19: Public health agencies are examining whether vitamin D supplements could reduce risks. BMJ.doi: 10.1136 / bmj.m2475.

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