The community suggests that vitamin D deficiency is a major determining factor in the severity and mortality related to COVID-19, and that systematic supplementation could drastically reduce these risks.

noli's read

The link between vitamin D and immunity is widely documented, particularly for respiratory health, but the extrapolation suggesting that 87% of deaths are preventable through supplementation (based on observational studies) is considered largely exaggerated by the scientific community. Subsequent meta-analyses, such as those from the Cochrane Library, indicate that while vitamin D is beneficial for preventing acute respiratory infections, the specific effect on COVID-19 mortality is not robustly established by randomized clinical trials (RCTs). The confusion between correlation (frail individuals are often deficient) and causation explains why certain observational studies show impressive results that are not confirmed in RCTs. The Reddit community is polarized here, oscillating between enthusiasm for an inexpensive solution and skepticism regarding simplistic statistical correlations. In short, supplementation is generally considered safe and beneficial for general health, but its effectiveness as a defense against COVID-19 mortality is overestimated in the initial post.

the sources

1. 1NIH Office of Dietary Supplements 2026
2. 2Manson JE et al. 2019
3. 3r/ScientificNutrition