Can we just copy what we do for Colds and Flu to prevent COVID-19?

As I mentioned in part 1, no. This is a very controversial subject, thus I write this carefully. It is important that as we discuss this topic, we do not contribute to the spread of misinformation. Please make sure that your sources are trustworthy and that you are referencing original sources, as important information is often taken out of context from secondhand sources. False reassurances, false alarms, and baseless recommendations all have the potential to cause harm, so be particularly mindful when sharing or receiving COVID-19 related information from friends and family. COVID-19 evidence is changing by the day. It’s likely that even some of the information presented in this article will be outdated before long, so make sure to always check multiple credible sources.

As a disclaimer, I am not a virologist, infectious disease specialist, or a public health specialist. I am a health expert with a strong understanding of pathophysiology, human nutrition, preventative health and lifestyle medicine. I have obtained 3 doctoral degrees, 3 bachelor degrees, and am board-certified in family medicine and chiropractic. I am writing this to help you focus on what matters most to your health.

Are there any supplements known to prevent, treat, or cure COVID-19?

No, not at this time. While a few supplements have gained popularity, the evidence of potential benefit for COVID-19 have not proven effective. Supplements are not strictly necessary and pale in comparison to the established preventative measures, such as hand washing, social distancing, mask wearing, and not touching our eyes, mouths and noses.

Currently, no one should claim that nutritional supplement protocols shown to help with cold/flu can be directly applied to COVID-19. For all we know, some supplements could even worsen specific manifestations of COVID-19. Let’s think about how viruses enter our body for a few examples. Half of colds are caused by rhinoviruses1 , 90% of which dock to intercellular adhesion molecule-1 (ICAM-1) to get access to the body2. The flu virus docks to sialic acid receptors to gain entrance into the body.3 SARS coronavirus-2 (SARS-CoV-2), the virus that causes COVID-19, attaches to ACE2 receptors in the mucus membranes of the upper respiratory system. This is important because nutrients such as vitamin A and vitamin D run the risk of increasing ACE2 receptors, which could potentiate the portal of entry for SARS-CoV-2 leading to COVID-19. As for whether or not we recommend supplements as we do with other viruses, there isn’t a definitive answer for now, as so much is dependent on individual risk factors. As of the time this piece is published, The International Society for Immunonutrition (ISIN) recommends the elderly specifically increase the daily intake of Vitamin C: 200–2,000 mg; Vitamin D: 400–4,000 IU (10–100 mcg) if blood levels are low; Vitamin E: 134–800 mg; and Zinc: 30–220 mg. However, they also add this disclaimer, “There is no specific evidence these nutritional measures can help protect against, or even lessen the effects of, COVID-19 infection.”

Are there supplements that can improve immune function?

Due to the complexity of the immune system, there is no single supplement or food that will affect every aspect. The immune system needs a variety of micronutrients to function optimally. Zinc, vitamin E, vitamin D, vitamin C, vitamin A, selenium, iron, B vitamins are some of the most important. No specific micronutrient is going to work wonders on its own, even if you megadose, but taking them together in reasonable amounts in the context of an overall healthful lifestyle can help, especially if you are insufficient or deficient. It is important to remember that the most important steps toward achieving good immune health are maintaining a balanced diet, proper hydration, restful sleep, regular exercise, and stress-control. Your immune system must be strong enough to fight off invading microbes, but it should not be imbalanced to the point where it overreacts and ends up damaging healthy cells.

In a double-blind randomized controlled trial of the use of intravenous vitamin C during acute respiratory distress syndrome (ARDS), vitamin C cut the mortality rate in half.4 People on the ventilators due to COVID-19 are dying primarily from ARDS based on current information, so does Vitamin C have its place? Perhaps, but on the other hand, studies using cell culture or mouse models have shown conflicting effects of vitamin C on interferon by either increasing it or decreasing it.5 Does this data indicate that vitamin C for COVID-19 prevention is potentially dangerous by causing unexpected effects on interferon and cytokine storm? Unfortunately, we have no hard evidence at this time, so we’re not sure. Thankfully, a clinical trial of intravenous (IV) vitamin C for severe COVID-19-induced pneumonia is underway as well as and many other studies like it. Remember that a single study is preliminary evidence, so even if it finds some benefit, more studies will be required for confirmation before the treatment can be recommended.6

Now that you are completely confused and have no idea what supplements to take, let’s talk proactive supplementation. In modest amounts, the following nutritional supplements may provide benefits to your immune system. Vitamin C, vitamin D, and zinc are reasonable options for proactive supplementation, particularly because vitamin D and zinc are frequently under-consumed. We briefly discussed Vitamin C above, so let’s talk about the other two.

Vitamin D is involved in many cellular processes, including the regulation of immune cells during infections.7,8 Low levels of vitamin D have been associated with reduced immune function9 and increased rates of acute respiratory infection.10

Zinc is a dietary mineral that can support the immune system and offer some protection against the common cold and some other viral diseases. Around one fifth of the world’s population is thought to be at risk for zinc deficiency.11,12 Zinc lozenges (Zinc Acetate) may reduce symptom severity for the common cold by inhibiting viral replication at the back of the throat.13,14,15 The effects on COVID-19, if any, are unknown. The established Tolerable Upper Intake Level (UL) is 40 mg/day.16 A maintenance dose of 5–15 mg/day is typically recommended. If you have high blood sugar or insulin resistance, consider taking 15–20 mg/day.

In general, your best bets for staving off these viral infections are to be practical, be smart, and be healthy. Eat a balanced diet, drink plenty of water, get restful sleep, exercise regularly, and try to control your emotional response to stressors of daily living. Also, continue all relevant COVID-19 protocol by washing your hands, practicing social distancing, wearing a mask, and refraining from touching your eyes, mouth, and nose as much as possible. It is important to remember that we are all unique and biochemical individuals with specific weaknesses and strengths. This individuality is why certain people are at higher risk regarding morbidity and mortality to COVID-19. If you think you have specific health concerns that put you at risk, or if you’re curious if you have a specific nutritional deficiency that could increase your susceptibility to COVID-19, it is important to meet with a physician that can customize a health program for you. Regarding the specific nutrients listed above, too much of a good thing could be a bad thing, but too little could also be bad. For your overall health and wellbeing, it is important to have balance and know your specific weaknesses so you can identify a process to make it your strength. I wish you well.

God Bless,
Dr. Bentley


1 Greenberg, S. B. Update on Human Rhinovirus and Coronavirus Infections. Semin. Respir. Crit. Care Med. 37, 555–571 (2016).

2 Novick, S. G., Godfrey, J. C., Godfrey, N. J. & Wilder, H. R. How does zinc modify the common cold? Clinical observations and implications regarding mechanisms of action. Med. Hypotheses 46, 295–302 (1996).

3 Lu, R., Müller, P. & Downard, K. M. Molecular basis of influenza hemagglutinin inhibition with an entry-blocker peptide by computational docking and mass spectrometry. Antivir. Chem. Chemother. 24, 109–117 (2015).

4 Fowler, A. A., 3rd et al. Effect of Vitamin C Infusion on Organ Failure and Biomarkers of Inflammation and Vascular Injury in Patients With Sepsis and Severe Acute Respiratory Failure: The CITRIS-ALI Randomized Clinical Trial. JAMA 322, 1261–1270 (2019

5 Carr, A. C. & Maggini, S. Vitamin C and Immune Function. Nutrients 9, (2017)

6 https://clinicaltrials.gov/ct2/show/NCT04264533

7 Brockman-Schneider RA, Pickles RJ, Gern JE. Effects of vitamin D on airway epithelial cell morphology and rhinovirus replication. PLoS One. (2014)

8 Telcian AG, et al. Vitamin D increases the antiviral activity of bronchial epithelial cells in vitro. Antiviral Res. (2017)

9 Prietl B, et al. Vitamin D and immune function. Nutrients. (2013)

10 Jolliffe DA, Griffiths CJ, Martineau AR. Vitamin D in the prevention of acute respiratory infection: systematic review of clinical studies. J Steroid Biochem Mol Biol. (2013)

11 Wessells KR, Singh GM, Brown KH. Estimating the global prevalence of inadequate zinc intake from national food balance sheets: effects of methodological assumptions. PLoS One. (2012)

12 Kumssa DB, et al. Dietary calcium and zinc deficiency risks are decreasing but remain prevalent. Sci Rep. (2015)

13 Hemilä H, et al. Zinc acetate lozenges for treating the common cold: an individual patient data meta-analysis. Br J Clin Pharmacol. (2016)

14 Hemilä H, Chalker E. The effectiveness of high dose zinc acetate lozenges on various common cold symptoms: a meta-analysis. BMC Fam Pract. (2015)

15 Hemilä H. Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage. JRSM Open. (2017)

16Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc.

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