In Immune Apocalypse I explain how vitamin D, a hormone usually associated with bone health, is also pivotal for marshalling the immune system and for possibly preventing COVID-19. In 2017 an extensive analysis of patient data from 11 321 participants in 25 randomised controlled trials showed that vitamin D supplementation protected against acute respiratory tract infections and that patients with very low (<25 nmol/L) serum 25-hydroxyvitamin D concentrations benefitted the most. Studies also reveal that those lacking vitamin D are more vulnerable to respiratory infections and do worse if they are infected with coronavirus.
We obtain vitamin D from sunlight and we need to bare our upper torsos completely for 5 minutes three times a week between the hours of 10 and 2 in summer, which extends to 20 minutes in winter, to achieve a vitamin D status that might be beneficial for our bones and our immune systems. A blood test can help to inform us if our levels are adequate.
With regard to preventing COVID-19 experts explain that the advantages of optimising vitamin D status are threefold. Firstly vitamin D stimulates that production of antimicrobial chemicals that directly inhibit viral replication in the lining of our lung tissue. Secondly vitamin D boosts the production of proteins which block the coronavirus from attaching to our lungs. Thirdly vitamin D reduces inflammation, a biochemical response associated with worsening outcomes in those who are infected.
As we synthesize vitamin D less efficiently from sunlight as we get older, finding out if we have enough vitamin D and supplementing if necessary might be prudent.