COVID-19 and Nutrition

Very limited evidence suggests that vitamin D may reduce disease severity in individuals with moderate to severe COVID-19; however, results are limited by small studies with imprecise results. The safety of vitamin D could not be determined due to lack of reporting. Results from ongoing studies are needed prior to providing a recommendation regarding the effectiveness and safety of vitamin D for treating COVID-19. 

A 2021 Cochrane review of individuals hospitalized with moderate to severe COVID-19 (two RCTs) reported low certainty of evidence that vitamin D may decrease the need for mechanical ventilation (RR 0.52). The effects of vitamin D on mortality and adverse events could not be determined due to inconsistent and imprecise results.   

A 2022 systematic review and meta-analyses of systematic reviews identified ten systematic reviews representing three to 13 primary studies of all designs reported that vitamin D2 or D3 (280,000-400,000 IU) was associated with a decreased odds of mortality (OR 0.48), a decreased odds of ICU admission (OR 0.35) and a decreased requirement for mechanical ventilation (OR 0.54). Adverse events were not reported. The results of the review represent very low certainty of evidence as results from RCTs and nonrandomized studies were combined, there was considerable overlapping of primary studies for each outcome, and the studies were small and heterogeneous.  

It is difficult to determine if there is an association between vitamin D deficiency and severe COVID-19 as risk factors for both conditions are similar (e.g. poor health, poor diet or a preexisting health condition such as diabetes, liver and kidney disease).