Scientific review published in Advances in Nutrition suggests high-dose vitamin C, vitamin D, and zinc may alleviate some complications caused by COVID-19

An extreme inflammatory response to COVID-19 infection, termed “cytokine release syndrome,” can lead to respiratory failure and death.  Research has shown that an overactive immune system may underlie cytokine release syndrome and other serious complications related to COVID-19.

Published in Advances in Nutrition, the international review journal of the American Society for Nutrition, “The Role of Immunomodulatory Nutrients in Alleviating Complications Related to SARS-CoV-2: A Scoping Review,” suggests that certain nutrients that support immune function may play a therapeutic role in the fight against COVID-19 disease.  Specifically, the authors, Parisa Jandaghi et al, reviewed the current body of evidence to determine the effect of immunomodulatory nutrients on outcomes among COVID-19 patients, including hospitalization, intensive care unit admission, oxygen requirement, and mortality.

To conduct their research, the authors performed a comprehensive search of the scientific literature, leading them to 19 human studies that met their inclusion criteria.  Collectively, the studies examined the impact of supplementation with vitamin C, vitamin D, vitamin B-12, zinc, and magnesium, both individually and in various combinations with each other.

Overall, the authors found that “supplementation with high-dose vitamin C, vitamin D, and zinc may alleviate the complications caused by COVID-19, including inflammatory markers, oxygen therapy, length of hospitalization, and mortality.”  Studies have shown, for example, that 24 grams a day of high-dose intravenous vitamin C for at least one week was “found to be useful in the clinical outcome of the studied patients and provided protective clinical effects.”  Lower doses of vitamin C for longer durations also proved helpful “for adjunctive care of inpatients with moderate to severe COVID-19 disease.”  The authors did caution that studies have shown extremely high doses of intravenous vitamin C can lead to renal dysfunction.

While zinc supplementation has shown some promise, the evidence of its effectiveness on COVID-19 patient outcomes is inconsistent.  The authors pointed to one study suggesting that a daily dosage of 440 mg of zinc sulfate led to a significant decrease in mortality among COVID-19 patients; however, other studies did not report a significant decrease in mortality despite a similar dosage.

The effectiveness of vitamin D supplementation for COVID-19 patients “appears to depend on dosage, duration of treatment, and baseline vitamin D status.”  For example, the authors pointed to some studies suggesting that supplementation with high amounts of vitamin D lowered the risk of mortality.  Other studies, however, found that supplementation with low-dose vitamin D actually increased the risk of death.

In addition to studies that examined the effect of individual nutrients on COVID-19 outcomes, there are some studies examining the effect of combining nutrients with promising initial results.  One study, for example, demonstrated that combination therapy with vitamin D, magnesium, and vitamin B-12 was associated with significantly fewer COVID-19 patients who required oxygen therapy and ICU support.

While overall the authors believe that the therapeutic use of vitamin C, vitamin D, and zinc may be effective in the fight against COVID-19 disease, they did concede that “studies were mixed regarding these effects.”  In order to strengthen the body of evidence, “more human randomized-controlled trials with larger sample sizes and high-dosage vitamin C, vitamin D, zinc, and combined therapy among different populations or various ethnicities merit further investigation.”