We already know that vitamin D can reduce the risk of respiratory tract infections. This is true with influenza and pneumonia.  Research is emerging that vitamin D may protect against COVID-19 infection as well.  In fact, hospitalized COVID-19 patients exhibited lower level vitamin D concentrations than age matched normals.  Researchers are speculating that this may have increased vulnerability to infection.

The mechanisms involve complex biochemistry but let me try and summarize:

  • Higher concentrations of vitamin D in the body interferes with the virus’s ability to replicate.  Replication increases the total number of virus particles and increases the threat of spread throughout the body. Limiting replication is GOOD!!!!
  • Higher concentrations of vitamin D in the body limit the number of inflammatory cells within the lungs.  Accumulation of inflammatory cells in the lungs can lead to infections like pneumonia and ARDS (Acute Respiratory Distress Syndrome) .


  • (Grant el al. 2020) recommend that people at risk of COVID-19 consider takin10,000 IU/ day of vitamin D3 for a few weeks to rapidly increase their 25(OH)D concentrations, followed by 5000 IU/ day to reduce the risk of infection.

D’Avolio, A.; Avataneo, V.; Manca, A.; Cusato, J.; De Nicolò, A.; Lucchini, R.; Keller, F.; Cantù, M. 25-Hydroxyvitamin D Concentrations Are Lower in Patients with Positive PCR for SARS-CoV-2. Nutrients 2020, 12, 1359.

Grant WB, Lahore H, McDonnell SL, et al. Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths. Nutrients. 2020;12(4):E988.