Rx Nutrition Resource Center

Rx Nutrition Resource Center

Disclosures: Cainzos-Achrirca, Michos and Thomas report no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
February 12, 2021
2 min read

Zinc, ascorbic acid fail to significantly decrease duration of SARS-CoV-2 symptoms

Disclosures: Cainzos-Achrirca, Michos and Thomas report no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
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There was no significant difference in the duration of SARS-CoV-2 symptoms among outpatients who took high-dose zinc gluconate, ascorbic acid or a combination of the two vs. usual care without supplementation, data showed.

“Limited evidence suggests that high doses of ascorbic acid and zinc gluconate may reduce duration of common cold symptoms and decrease the severity of symptoms,” Suma Thomas, MD, MBA, a physician in the cardiology department at Cleveland Clinic, and colleagues wrote. “However, the role of zinc gluconate and ascorbic acid in decreasing symptoms and improving recovery in patients diagnosed with SARS-CoV-2 infection is uncertain.”

The mean number of days until patients achieved a 50% reduction in SARS-CoV-2 symptoms was 6.7 in patients who received neither zinc gluconate nor ascrobic acid; 5.9 in those who only took zinc gluconate; 5.5 in those who only took ascorbic acid; and 5.5 in those who took both.
Reference: Thomas S, et al. JAMA Netw Open. 2021;doi:10.1001/jamanetworkopen.2021.0369.

The researchers randomized 214 outpatients (mean age, 45.2 years; 61.7% women) with a positive SARS-CoV-2 diagnosis in an approximate 1:1:1:1 ratio to receive 10-day treatment with: 50 mg of zinc gluconate; 8,000 mg of ascorbic acid; both supplements or; usual care without supplementation. The primary endpoint was the number of days until a patient reached a 50% reduction in severity of their fever, cough, shortness of breath and fatigue. Each symptom was rated on a four-point scale at baseline. The secondary outcomes included the number of days a patient needed to reach a total symptom severity score of zero, cumulative severity score at day 5, hospitalizations, deaths, adjunctive prescribed medications and adverse events tied to the supplements.

According to Thomas and colleagues, patients who received usual care had a reduction in symptoms in a mean of 6.7 days. Symptoms were reduced in those who received zinc gluconate after a mean of 5.9 days, while those who received ascorbic acid or both each needed a mean of 5.5 days (overall P = 0.45). There was no significant difference in secondary outcomes, according to the researchers. They stopped the trial early after an interim analysis of the data demonstrated a lack of significant benefit with the supplements.

Thomas and colleagues acknowledged that previous data have suggested that zinc supplementation can fight infection and ascorbic acid can affect the immune system.

“However, based on the current study, these supplements cannot be recommended to reduce symptom morbidity in such patients,” they wrote.

In a related editorial, Erin D. Michos, MD, MHS, director of women’s cardiovascular health at Johns Hopkins School of Medicine, and Miguel Cainzos-Achirica, MD, MPH, PhD, an assistant professor of preventive cardiology at Houston Methodist, said future research should investigate how vitamins and supplements may help patients with COVID-19, so long as it is conducted carefully.

“The best evidence to guide clinical recommendations comes from well-designed [randomized clinical trials],” Michos and Cainzos-Achirica added. “Given the widespread public use of supplements, such as zinc and ascorbic acid, for the prevention and treatment of viral infections, we applaud the ... study investigators for adding rigorous science by testing their efficacy and challenging popular beliefs. Unfortunately, these two supplements failed to live up to their hype.”


Michos ED and Cainzos-Achririca. JAMA Netw Open. 2021;doi:10.1001/jamanetworkopen.2021.0431.

Thomas S, et al. JAMA Netw Open. 2021;doi:10.1001/jamanetworkopen.2021.0369.