There is no clear evidence that anything other than avoiding exposure can reliably prevent contraction of SARS-CoV-2 (the virus that causes COVID-19).
There is, however, evidence that a number of nutrients can either reduce your chance of contracting coronavirus or reduce the severity and length of illness if you do contract the virus. I don’t make this claim lightly, and the following content supports that statement with summaries and links to articles published in respected journals. Please take the time to follow some or all of the links.
This article will focus on nutraceutical supplements, not traditional herbal approaches, which I will cover in a later article. And, although it could go without saying, I’ll say it anyway. Adequate sleep, reducing stress, eating a healthy diet, and moderate, regular exercise are all important and effective ways to regulate your immune system and keep inflammatory responses in check. Immune system support can potentially reduce your chance of infection, and maybe even more importantly, inflammatory response regulation can reduce the likelihood that an infection will lead to more severe illness.
I have found evidence that maintaining adequate levels of vitamin D, vitamin C, quercetin and zinc through daily supplementation is warranted, especially in older patients or patients with other health issues that put them at higher risk. I studied the data (or lack of it) for many other products, including CBD oil, colloidal silver, a number of essential oils, garlic and melatonin, and did not find sufficient evidence for daily supplementation.
For those not wanting to delve into the details, please feel free to go directly to the “EBANM COVID-19 Prophylaxis” I’m recommending for all of my patients. If you’re interested in the details, let’s begin with vitamin D.
A 2017 BMJ systematic review and meta-analysis found that vitamin D supplementation significantly decreased the risk of acute respiratory infections, especially in those receiving daily vitamin D (versus less frequent large doses). “Our study reports a major new indication for vitamin D supplementation: the prevention of acute respiratory tract infection.” ”Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis.” BMJ. Martineau, et al, 2017.
Another review published recently (May, 2020), suggests that people at increased risk for influenza or COVID-19 consider taking vitamin D, with the goal of raising vitamin D concentrations to 40–60 ng/mL. Furthermore, they state: “Through several mechanisms, vitamin D can reduce risk of infections. Those mechanisms include inducing cathelicidins and defensins that can lower viral replication rates and reducing concentrations of pro-inflammatory cytokines that produce the inflammation that injures the lining of the lungs, leading to pneumonia.” “Evidence that Vitamin D supplementation could reduce the risk of influenza and COVID-19 infections and deaths.” Nutrients. Grant, et al, 2020.
A more general review states that low vitamin D levels are associated with an increased risk of viral and bacterial respiratory infections, along with other respiratory diseases, including tuberculosis, asthma, and chronic obstructive pulmonary disease. “All the reviewed articles state that Vitamin D deficiency is very common among patients with respiratory diseases.” “A review of Vitamin D effects on common respiratory diseases.” J Res Pharm Pract. Hejazi, et al, 2016.
And a less compelling, but still interesting, recent “preprint” article details how vitamin D, quercetin and estradiol alter the expression of genes encoding the protein targets of SARS-CoV-2. “Vitamin D and Quercetin have been identified as putative COVID mitigation agents.” Interestingly, the article also posits an explanation for the higher male mortality rates associated with COVID-19. “Vitamin D, quercetin and estradiol… mitigation of COVID-19.” Chem Rxiv. Glinskii, et al, 2020.
Vitamin C & Quercetin
Vitamin C is a potent antioxidant that contributes to immune defenses in a number of different ways. It also has anti-inflammatory effects that can limit the progression of disease. This article gives the details, and states that: “supplementation with vitamin C appears to be able to both prevent and treat respiratory and systemic infections. Prophylactic prevention of infection requires dietary daily vitamin C intake…”. “Vitamin C and Immune Function”. Nutrients. Carr, et al, 2017.
The following studies evaluated the antiviral effect of vitamin C in vivo and its related mechanism against the influenza virus. They explain that the antiviral benefits of vitamin C are likely due to its immunomodulatory properties, predominantly by increasing the production of interferon-α/β and downregulating pro-inflammatory cytokines, rather than a direct antiviral effect. We know that COVID-19 mortality is associated with the “cytokine storm,” so this may explain why vitamin C can reduce the severity of the illness. “The antiviral properties of vitamin C.” Expert Review of Anti-Infective Therapy. Biancatelli, et al, 2020. “Vitamin C is an essential factor on the antiviral immune responses…”. Immune Network. Kim et al, 2013.
Quercetin is an antioxidant that also has broad antiviral properties. It has been shown to reduce viral replication in human cell culture lines for a wide variety of viruses – including the coronaviruses that cause the common cold. This study shows immunomodulatory and antiviral activity against rhinovirus respiratory infections. More importantly, the paper details how quercetin inhibits cytokine expression, which can reduce the “cytokine storm” that is frequently the cause of death in many COVID-19 patients. “Quercetin inhibits rhinovirus replication in vitro and in vivo.” Antiviral Research. Ganesan, et al, 2012.
Zinc can modulate antiviral and antibacterial activity. “In vitro experiments demonstrate that Zinc possesses antiviral activity through inhibition of SARS‑CoV RNA polymerase.” Zinc also regulates inflammatory responses that may reduce the severity of illness. “Zinc possesses anti‑inflammatory activity by inhibiting NF‑κB signaling and modulation of regulatory T‑cell functions that may limit the cytokine storm in COVID‑19”. “Zinc and respiratory tract infections: Perspectives for COVID-19 (Review).” Intl Journal of Molecular Med. Skalny, et al, 2020.
Zinc is an essential mineral that the immune system relies upon for an effective antiviral response. This paper explores how its antiviral properties generate both innate and acquired immune responses. “The Role of Zinc in Antiviral Immunity.” Advances in Nutrition. Read, et al, 2019.
A number of papers have studied the effects of zinc supplementation on both the prevention of acute lower respiratory infections (ALRIs) as well as the length of illness due to respiratory infection with zinc supplementation. “Zinc supplementation has been shown to have a preventive effect against respiratory infection. The study found that ALRI cessation was faster in children who received zinc supplementation and that their hospital stay was shorter”. “A Randomized Controlled Trial of Zinc Supplementation.” Pediatric Rep. Rerksuppaphol, et al, 2019. “Zinc: Role in Immunity, Oxidative Stress and Inflammation.” Clinical Nutrition Metabolic Care. Prasad, et al, 2009.
Finally, though SARS-Cov-2 acts very differently than the various viruses that cause the common cold, there are also some similarities in regard to how the immune system responds. This Cochrane review confirms Zinc’s ability to reduce the duration and severity of cold symptoms, and “when supplemented for at least 5 months, it reduces cold incidence.” Cochrane reviews have a reputation for being extremely rigorous. Though direct evidence that Zinc can prevent infection of SARS-CoV-2 is lacking, this is strong evidence that it can prevent other acute viral infections. “Zinc for the common cold.” Cochrane Database Syst Rev. Singh, et al, 2011.
For details on the specific products we recommend, as well as dose and frequency information, please see our “EBANM COVID-19 Prophylaxis” article.