Vitamins and Dietary Supplements For the Prevention of COVID-19?

While evidence continues to support that certain behaviors, such as maintaining a physical distance of 6 feet, wearing a mask, and washing hands frequently are the most effective methods of preventing COVID-19, there remains much information, and misinformation, regarding the use of certain vitamins and dietary supplements to do the same.

Recently, the Eastern Virginia Medical School published their “Critical Care Management Protocol” for COVID-19. While acknowledging that “there is very limited data (and none specific for COVID-19)”, the authors indicated that “the following ‘cocktail’ may have a role in the prevention/mitigation of COVID-19 disease”.

For prophylaxis, the protocol recommends vitamin C (500 mg) and quercetin (250 mg-500 mg) twice a day, zinc (75 mg-100 mg) once a day, vitamin D3 (1,000-4,000 IU) once a day and melatonin, slow-release (from 0.3 mg to up to 2 mg) once a day at night. Famotidine (20 mg-40 mg) once a day may be added as an option.

However, since these vitamins and supplements are available without prescription, it is conceivable that some patients may take more than the doses recommended in the protocol. This is of concern to dentistry because the concomitant use of these vitamins and supplements in high doses may result in synergistic adverse effects with dental implications.

The use of vitamin C to reduce both the risk of contracting common colds as well as the symptoms of common colds, is well established. Vitamin C is an antioxidant and is necessary for the proper function of our immune systems. Quercetin, a plant flavonoid, gained notoriety when researchers in China found that quercetin and other small molecules bind to the spike protein of the SARS-CoV-1 coronavirus, interfering with its ability to infect host cells. Zinc is thought to be essential for immune-cell development, and its use in reducing the risk of contracting respiratory infections and reducing the severity of their symptoms is well established. 

However, when taken together, vitamin C and quercetin are synergistic. While this may boost their anti-viral activity, it may also result in nausea and vomiting and kidney damage. High doses of zinc may also cause nausea and vomiting and kidney damage.

Deficiency of vitamin D3 has been implicated in several respiratory disorders. Studies conducted early in the COVID-19 pandemic found that countries with a high prevalence of hypovitaminosis D were more likely to have serious outbreaks and higher mortality rates. However, high doses of vitamin D might overstimulate the immune system, which would be problematic in COVID-19. In addition, too much vitamin D may, again, cause kidney damage.

Melatonin is most often used to improve sleep, which may be beneficial for immunity. Melatonin is also thought to reduce inflammation and fibrosis in the lungs, which are common complications for patients with COVID-19. However, high doses of melatonin may increase the risk of CNS depression, especially when taken concomitantly with benzodiazepines and opioid analgesics.

According to a recent review published in Annals of Pharmacotherapy, there is an overall lack of evidence supporting the use of dietary supplements for the prevention or treatment of COVID-19. “Patients and providers should not rely on dietary supplements to prevent or cure COVID-19,” the authors concluded.


Marik P. EVMS Critical Care COVID-19 Management Protocol (accessed 8/1/20)

Adams, William, et al. Myth Busters: Dietary Supplements and COVID-19. SAGE Journals 2020; 8: 820-826

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