Coronavirus patients who were treated with high doses of zinc and vitamin C did not show "significant" improvement compared to traditional treatments, according to a recent US-based clinical trial.

Though medical experts advise the consumption of vitamin C and zinc to help gain momentum in fighting the virus, the study showed the opposite with patients who had already contracted COVID-19.

"In this randomized clinical trial of 214 ambulatory patients diagnosed with SARS-CoV-2 infection, treatment with high-dose zinc gluconate, ascorbic acid, or a combination of the two supplements did not significantly decrease the duration of symptoms compared with standard of care," a co-author of the clinical trial, Dr. Milind Desai, told Anadolu Agency.

Initially, the trial sought to show whether high-dose zinc or high-dose vitamin C, also known as ascorbic acid, reduces the severity or duration of symptoms compared with usual care among patients infected with COVID-19.

It was conducted from April 27 to Oct. 14, 2020, among patients who received outpatient care at clinical facilities.

"This was a trial based only in the US, albeit at multiple centers in Ohio and Florida within the same health system," said Desai, a cardiologist and professor of medicine at the Cleveland Clinic, adding that 72% of participants were white and 24% Black.

The patients were randomized into four groups to receive either 10 days of 50 mg of zinc gluconate, 8,000 mg of ascorbic acid, both agents or standard care.

Meanwhile, the primary endpoint was the number of days it would require to achieve a 50% reduction in symptoms, including the severity of fever, cough, shortness of breath and fatigue, each rated on a four-point scale.

Secondary endpoints included days required to reach a symptom severity score of zero, cumulative severity score at day five, hospitalizations, deaths, adjunctive prescribed medications and adverse effects of study supplements.

The study was stopped for a "low conditional power for benefit with no significant difference" among the four groups for the primary endpoint, according to the study article.

"There was no significant difference in secondary outcomes among the treatment groups," it said.

Patients who received usual care without supplements achieved a 50% reduction in symptoms at a mean of 6.7 days compared with 5.5 days for the vitamin C group, 5.9 days for the zinc gluconate group, and 5.5 days for the group receiving both, the study revealed.

Asked whether the results of the randomized trial with 214 participants would be applicable globally, Desai said: "Whether it would be applicable to the global population was not tested."

Desai also underlined that he was not aware of "any rigorously performed randomized studies" on supplements -- such as special vitamins, herbs, therapy or other medications -- that "conclusively show" they reduce the risk of contracting the virus.

"The best advice is social distancing, hand washing and wearing masks as is recommended by public health organizations like CDC [Centers for Disease Control and Prevention] and the WHO [World Health Organization]," he said.

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