Evidence That Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths

Abstract

The world is in the grips of the COVID-19 pandemic. Public health measures that can reduce the risk of infection and death in addition to quarantines are desperately needed. This article reviews the roles of vitamin D in reducing risk of respiratory tract infections, knowledge about the epidemiology of influenza and COVID-19, and how vitamin D supplementation might be a useful measure to reduce risk. Through several mechanisms, vitamin D can reduce risk of infections. Those mechanisms include inducing cathelicidins and defensins that can lower viral replication rates and reducing concentrations of pro-inflammatory cytokines that produce the inflammation that injures the lining of the lungs, leading to pneumonia, as well as increase concentrations of anti-inflammatory cytokines. Several observational studies and clinical trials reported that vitamin D supplementation reduced risk of influenza, whereas others did not. Evidence supporting the role of vitamin D in reducing risk of COVID-19 includes that the outbreak occurred in winter, a time when 25-hydroxyvitamin D [25(OH)D] concentrations are lowest; that the number of cases in the Southern Hemisphere near the end of summer are low; that vitamin D deficiency has been found to contribute to acute respiratory distress syndrome, and that case-fatality rates increase with age and with chronic disease comorbidity, both of which are associated with lower 25(OH)D concentration. To reduce risk of infection, it is recommended that people at risk of influenza and/or COVID-19 consider taking 10,000 IU/d of vitamin D3 for a few weeks to rapidly raise 25(OH)D concentrations, followed by 5000 IU/d. The goal should be to raise 25(OH)D concentrations above 40–60 ng/ml (100–150 nmol/l). For treatment of people who become infected with COVID-19, higher vitamin D3 doses might be useful. Randomized controlled trials and large population studies should be conducted to evaluate these recommendations.

Multivariate Analysis of Factors Affecting COVID-19 Case and Death Rate in U.S. Counties: The Significant Effects of Black Race and Temperature

“…The mechanism through which temperature may execute its mitigative effects remains unclear, though it has already been posited that increased vitamin D levels due to greater sun exposure may result in better immune response against the SARS-CoV-2 virus, as it has been shown to do within the context of other viruses. 42,43 Notably, when temperature is substituted out of our final model for other vitamin D proxies, such as average daily sunlight and latitude above and below 37 degrees, the results are also highly significant in the same direction. Including these variables together in the model resulted in multicollinearity, which suggests that they are most likely measuring the same effect.…”

“…41 Vitamin D has been suggested as a potentially mitigative factor in the COVID-19 pandemic due to its important modulatory effect on immune response. 42,43 Furthermore, vitamin D deficiency has been implicated in numerous adverse health conditions such as acute respiratory syndromes, tuberculosis, cardiovascular disease, autoimmune disease, and some cancers. 44 This higher prevalence of vitamin D deficiency in darker-skinned individuals is thought to largely be due to increased melanin pigmentation, which absorbs significantly more radiation from sunlight and thereby reduces the available ultraviolet-B radiation that is needed to trigger natural vitamin D production in the skin.…”

Assessment of self-medication practices in the context of the COVID-19 outbreak in Togo

“…While chloroquine and hydroxychloroquine are controlled medicines that are sold in pharmacies, this is not the case for vitamin C. In our study, vitamin C was used by approximately one-third (27.6%) of the participants. Several studies have suggested the effectiveness of a high dose of vitamin C in the management of COVID-19 [ 34 , 35 ]. However, it is also important to note that high doses of vitamin C may cause side effects, most specifically an increased risk of kidney stones [ 36 ].…”

UV, ozone, and COVID-19 transmission in Ontario, Canada using generalised linear models

“…UV also helps generate vitamin D in the body through skin exposure. Given the reported link between vitamin D and COVID-19, it is possible that UV helps prevent COVID-19 through its generation of vitamin D and subsequent positive immune effects ( Grant et al, 2020 ; McCartney and Byrne, 2020 ). Our UV findings found a negative association with COVID activity by R t overall.…”