Two small randomized clinical trials were not able to demonstrate a benefit of high dose zinc, vitamin C, or vitamin D3 for patients with COVID-19.
The first study, conducted in the U.S., examined whether high-dose zinc and/or high-dose ascorbic acid (vitamin C) reduced the severity or duration of symptoms compared to usual care among 214 adults diagnosed with COVID-19. The participants (who were not hospitalized) received 50 milligrams (mg) zinc gluconate, 8,000 mg ascorbic acid, both, or standard care for 10 days. There was no significant difference in outcomes between participants receiving standard care (no supplements) and those in the supplement groups.
The second randomized controlled trial gave 240 patients hospitalized in Brazil with moderate to severe COVID-19 a single dose of 200,000 IU of vitamin D3 or a placebo. While serum levels of 25-hydroxy-vitamin D went up in the supplement group, the hospital length of stay was no different than the control group. Admission to intensive care units, need for mechanical ventilation, and death rate was also not significantly different between the two groups. [Editor-in-chief’s note: These results are not definitive. Small studies can miss moderate benefits.]
While experts around the world continue to search for ways to treat COVID-19 infection, doing our best to prevent exposure through social distancing, mask wearing, and hand washing is still essential as the vaccine rolls out.