Antioxidant therapies for COVID-19 show mixed results

Key takeaways:

• Some antioxidant therapies like zinc and vitamin C reduced hospitalization stays and improved symptoms of COVID-19.
• More trials are needed to confirm the results, a researcher said.

CHICAGO — Antioxidant therapies showed varying levels of effectiveness when used as a treatment for COVID-19, according to results of a recent systematic review and meta-analysis presented at NUTRITION.

“These results are important because they could help manage health care capacity during the pandemic,” Benita Hosseini, Dr, an assistant professor at the University of Toronto in Canada, told Healio.

According to Hosseini, antioxidant therapies can suppress oxidative stress and inflammation triggered by viral infections such as SARS-CoV2.

Because of this, “exploring the potential of nonspecific treatments like antioxidants is crucial even as COVID-19 transitions to endemic status,” she said.

Hosseini searched six databases for literature on antioxidant therapies — including vitamin A, vitamin C, zinc and combination treatments — for COVID-19 vs. placebo. She identified 3,306 articles, of which 25 were eligible and included for quantitative synthesis and five were eligible for meta-analysis.

Among the 25 studies, Hosseini reported that:

• eight were high quality with low bias;
• six had “some concerns”; and
• 11 were low quality with high bias.

“These biases could be attributed to the challenges faced during the COVID-19 pandemic, like changes in research methods and challenges in keeping participants, which could lead to attrition bias and affect the results,” Hosseini said.

When focusing on individual antioxidants, Hosseini found that the zinc interventions had mixed results, “with some studies showing that zinc could shorten symptoms and reduce ICU admissions, while others saw no significant improvement in recovery times.”

She also noted that the vitamin A studies showed improvements in inflammatory markers, whereas the vitamin C studies showed inconsistent effects on clinical improvement and hospitalization.

After further investigating vitamin C in the meta-analysis, Hosseini said there was no significant difference in C-reactive protein (CRP) levels, ICU stay duration or mortality, although there was a slight trend favoring reduced duration of hospitalization.

“Our findings indicate that while high doses of vitamin C might improve recovery time and reduce hospital stays, its effect on mortality and ICU duration is less clear,” she said.

Meanwhile, combination treatments including antioxidants like vitamin A, vitamin C, vitamin E, zinc and selenium improved COVID-19 symptom clearance by more than 2 days, reduced hospitalization duration by more than 1 day and reduced hospital mortality and 28-day mortality, Hosseini said. However, these treatments did not have a significant impact on the need for artificial ventilation or changes in CRP levels, she added.

“To our knowledge, this study provides the most comprehensive pooled data on the effects of antioxidant therapy on COVID-related outcomes,” she said. “Current outpatient treatments for SARS-CoV-2 can reduce hospitalizations and deaths but are often expensive, have limited eligibility and can cause side effects. This highlights the need for safe, alternative therapies.”

Hosseini added that antioxidant therapy “could be a potential alternative because it might achieve similar benefits as current drugs but with fewer side effects and at a lower cost.”

“Before making any recommendations for the public, we need well-designed, larger-scale, robust clinical trials to confirm results in outpatients,” she said.

Hosseini will continue to investigate outpatient treatments for COVID-19 in the Canadian Adaptive Platform Trial of Treatments for COVID in Community Settings, or CanTreatCOVID.

“As part of CanTreatCOVID, we will examine the effectiveness of combined antioxidant therapy consisting of selenium, zinc, lycopene and vitamin C,” she said. “With antioxidants widely available at a fraction of the cost of current COVID-19 treatments and without the need for a prescription or close medical supervision, this alternative therapy has the potential to reach and benefit communities both in Canada and worldwide.”

For more information:

Benita Hosseini, Dr, can be reached at benita.hosseini@utoronto.ca.