Immune-boosting supplements do not lessen risk of death from COVID-19, review finds

Reviewed by Emily Henderson, B.Sc.Feb 17 2022

A new review of COVID-19 hospitalization data by researchers at The University of Toledo has found that taking immune-boosting supplements such as vitamin C, vitamin D and zinc do not lessen your chance of dying from COVID-19.

Early in the pandemic, healthcare providers tried a variety of micronutrients as potential therapies for the new illness. More recently, supplements have been promoted by some as an alternative to the safe and proven vaccines.

However, Dr. Azizullah Beran said there's been little evidence those strategies work, despite the enduring interest in them.

A lot of people have this misconception that if you load up on zinc, vitamin D or vitamin C, it can help the clinical outcome of COVID-19. That hasn't been shown to be true."

Dr. Azizullah Beran, internal medicine resident, The University of Toledo College of Medicine and Life Sciences

Beran is the lead author on a new paper that significantly strengthens the emerging medical consensus that micronutrient supplements are not an effective treatment for COVID-19.

He and his collaborators reviewed 26 peer-reviewed studies from around the globe that included more than 5,600 hospitalized COVID-19 patients. Their analysis found no reduction in mortality for those being treated with vitamin D, vitamin C or zinc compared to patients who did not receive one of those three supplements.

Their analysis did find that treatment with vitamin D may be associated with lower rates of intubation and shorter hospital stays, but the researchers say more rigorous study is needed to validate that finding.

Vitamin C and zinc were not associated with shorter hospital stays or lowering the chance a patient would be put on a ventilator.

While the study predominately looked at patients who were already sick and hospitalized with COVID-19 when given the supplements, researchers did analyze a smaller subset of individuals who had been taking vitamin D prior to contracting the virus. They found no significant difference in the mortality rate of that population either.

The paper is published in the journal Clinical Nutrition ESPEN.

"It's important for people to understand that taking a lot of these supplements does not translate into better outcomes," said Dr. Ragheb Assaly, a UToledo professor of medicine and the paper's senior author. "The other important message is that the answer to this disease is the vaccine. Micronutrient supplements will not offset the lack of vaccination or make you not need the vaccine."

Researchers caution that the study shouldn't be interpreted as saying vitamin and mineral supplements are bad or should be avoided, but rather make it clear that they are not effective at preventing COVID-19 deaths.

Beran and Assaly say it's possible that some COVID-19 patients who are malnourished or otherwise deficient in micronutrients may benefit from taking supplements, but that's because their bodies already lack essential nutrients -; not because vitamin D or vitamin C are effective against the virus.

"What we're saying is this: If you don't medically need these supplements, don't take them thinking they're protective against COVID-19," Beran said. "They're not going to prevent you from getting it and they're not going to prevent you from dying."