Preventing vitamin D deficiency during the COVID-19 pandemic: UK definitions of vitamin D sufficiency and recommended supplement dose are set too low.

There is growing evidence linking vitamin D deficiency with risk of COVID-19. It is therefore distressing that there is major disagreement about the optimal serum level for 25-hydroxyvitamin D (25(OH)D) and appropriate supplement dose. The UK Scientific Advisory Committee for Nutrition has set the lowest level for defining sufficiency (10 ng/ml or 25 nmol/L) of any national advisory body or scientific society and consequently recommends supplementation with 10 micrograms (400 IU) per day. We have searched for published evidence to support this but not found it. There is considerable evidence to support the higher level for sufficiency (20 ng/ml or 50 nmol/L) recommended by the European Food Safety Authority and the American Institute of Medicine and hence greater supplementation (20 micrograms or 800 IU per day). Serum 25(OH)D concentrations in the UK typically fall by around 50% through winter. We believe that governments should urgently recommend supplementation with 20-25 micrograms (800-1,000 IU) per day.