Vitamin C and Zinc Likely Don't Help COVID-19 Symptoms

Since the start of the pandemic, people have searched for supplements to help speed up recovery from COVID-19. Now, new research has found that two supplements in particular—zinc and vitamin C—are unlikely to be helpful.

The February study, which was published in JAMA, randomly assigned 214 patients with confirmed cases of COVID-19 to either receive a high dose of zinc, vitamin C, a combination of both, or a placebo. The researchers tracked how many days it would take for study participants to reach a 50% reduction in symptoms, including fever, cough, shortness of breath, and fatigue.

The researchers found that people who received usual care without supplements had a 50% reduction in their symptoms in about 6.7 days compared with 5.5 days for the vitamin C group, 5.9 days for the zinc group, and 5.5 days for the group that received both. While there was a slight difference in the timeline, it was not considered statistically significant.

The study was eventually halted early due to the lack of statistical significance and the low number of enrolled patients. People who took the supplements were also more likely to have side effects like nausea, diarrhea, and stomach cramps. An accompanying editorial noted that “unfortunately, these two supplements failed to live up to their hype.”

“When we began this trial, there was no research to support supplemental therapy for the prevention or treatment of patients with COVID-19,” study co-author Milind Desai, MD, director of clinical operations in Cleveland Clinic’s Heart Vascular & Thoracic Institute, said in a press release. “As we watched the pandemic spread across the globe, infecting and killing millions, the medical community and consumers alike scrambled to try supplements that they believed could possibly prevent infection, or ease COVID-19 symptoms, but the research is just now catching up.”

Desai also said that, while vitamin C and zinc “proved ineffective” as a form of treatment for COVID-19, he points out that other supplements are still being studied.

The data on both supplements has been mixed so far, with the study co-authors writing that past research has been “inconsistent, with some trials suggesting that high doses of ascorbic acid and zinc gluconate may reduce the duration of common cold symptoms and decrease the severity of symptoms, while other studies have shown no benefit.”

Zinc and Vitamin C for the Common Cold

Zinc is a nutrient that helps the immune system fight off invading bacteria and viruses. The body needs zinc to make proteins and DNA, and the nutrient helps wounds to heal.

Zinc is required in order for the body’s immune system to do its job, and people with low levels of zinc may have a higher risk of getting pneumonia and other infections. Research suggests that using zinc lozenges or syrup can help speed up recovery from the common cold by up to a day if it’s taken within 24 hours of developing symptoms. However, studies are still ongoing. 

Vitamin C, also known as ascorbic acid, is an antioxidant that helps support the immune system’s function. Vitamin C also protects the body’s cells from damage caused by free radicals, which are compounds formed when the body converts food into energy.

Research has found that vitamin C supplements can reduce the length of time for a cold by 8% in adults and 14% in kids.

 Vitamin C and Zinc for COVID-19 Care

Currently, there are ongoing clinical trials in the U.S. and China that are looking into the role of IV vitamin C in reducing the risk of respiratory failure and mechanical ventilation in COVID-19 patients.

There is evidence that being deficient in zinc may reduce the body’s production of antibodies, theoretically making it difficult to fight off COVID-19. And one study found that critically ill patients—not those with COVID-19—who were given high doses of vitamin C had a shorter length of time on a ventilator and were hospitalized for shorter periods of time than those who did not take the vitamin.

But despite some research suggesting that there’s a potential for zinc and vitamin C to help fight COVID-19, experts point out that’s not the same as a real connection. “I am not surprised by the findings because the effects of these supplements on other viral infections is pretty minimal,” Richard Watkins, MD, an infectious disease physician and a professor of internal medicine at the Northeast Ohio Medical University, tells Verywell.

Jamie Alan, RPH, PharmD, PhD, an assistant professor of pharmacology and toxicology at Michigan State University, agrees. “The data regarding zinc and vitamin C for treatment of viral disease has never been very convincing,” she tells Verywell.

But Alan says the data on the use of zinc and vitamin C to prevent illness is “a bit stronger.”

“Zinc and vitamin C seem to have a better effect when the virus is first infecting a person,” she says. “There is data that suggests that zinc may decrease viral attachment and local infection before a systemic infection takes place.”

If you’re interested in taking either of these supplements to try to prevent or treat COVID-19, Alan says it doesn’t hurt. Just know that it may not do much. “Zinc and vitamin C supplementation is generally very safe, so in most cases, it would not hurt to try these supplements,” Alan says.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.