claim: “Research illustrates a clear correlation between vitamin D deficiencies and (higher) COVID-19 mortality rates.”
evidence: Vitamin D deficiency has been strongly associated with various health outcomes, including all-cause mortality [68]. A 2014 Cochrane meta-analysis showed a relevant and significant lower all-cause mortality of ~7% and cancer mortality of ~13% in patients who received vitamin D3 [69]. The results of a meta-analysis by using individual participant data conducted by Gaksch et al., analyzing almost 17,000 individuals, showed a strong association between low 25(OH)D and increased risk of all-cause mortality [70]. Using a Mendelian randomization with genetic variants in the vitamin D synthesis pathway, the analysis of Aspelund et al. supports a causal relationship between vitamin D deficiency and increased all-cause mortality. However, despite a cohort of >10,000 participants, it was still too underpowered to confirm a causal relationship [71]. [...] Zhang Y, Fang F, Tang J, Jia L, Feng Y, Xu P, et al. Association between vitamin D supplementation and mortality: systematic review and meta-analysis. BMJ. 2019;366:l4673. https://doi.org/10.1136/bmj.l4673