The new research suggests what we already knew based on Vitamin D functions - indirectly through various mechanisms, vitamin D has an effect on ongoing infections - respiratory tract diseases and extramedullary pneumonia – are some examples. Vitamin D supplementation has also been shown to reduce the risk of common colds.
Most likely indirectly, vitamin D has an effect on lowering the rate of viral replication and reduces pro-inflammatory cytokines concentration which can damage the lung structure. Reducing vitamin D deficiency is thought to inhibit CD26 activity, a particle that facilitates coronavirus intrusion.
Vitamin D may also attenuate inflammatory responses caused by interferon-gamma (IFNγ) and interleukin-6 (IL-6), which higher activity projects very poorly for critically ill, ventilated patients, including those with Covid-19.
Several observational and clinical studies have also shown that vitamin D supplementation reduces the risk of influenza.
Pieces of evidence supporting a role for vitamin D in reducing COVID-19 risk are that the outbreak occurred in winter when 25-hydroxyvitamin D concentrations are lowest; mortality rates for coronavirus infection increase with age and coexisting chronic diseases, and are often associated with lower 25-hydroxyvitamin D concentrations, and that vitamin D deficiency contributes to acute respiratory distress syndrome.
What doses of vitamin D does the research suggest?
To reduce the risk of influenza and/or COVID-19 infection, it is recommended that those at risk consider taking 10000 IU of vitamin D3 daily (250 μg) for several weeks to rapidly raise Vitamin D concentrations, followed by a maintenance dose of 5000 IU daily (125 μg).
The goal should be to raise 25-hydroxyvitamin D concentrations above 40-60 ng/ml (100-150 nmol/l). Higher doses of vitamin D3 may be useful in doing so, resulting in the support of treating the individuals infected with COVID-19.