Reducing the risk of covid-19: adequate doses of vitamin D are needed
The 10 mcg (400 IU) vitamin D supplement recommended by Public Health England is verging on the homoeopathic – it would raise blood 25(OH)D levels over 2-3 months by only around 4 nmol/L, leaving someone who is vitamin D deficient still deficient!
Most adults (and especially the elderly, those with dark skins, and those who are overweight or obese) will require much bigger doses to achieve optimal 25(OH)D levels (100-150 nmol/L; 40-60 ng/mL) - 5,000 IU (125 mcg)/day (or even more) is not unusual. (As a general rule of thumb, a dose of 1,000 IU (25 mcg) will raise blood 25(OH)D levels by around 10 nmol/L.) The potential for toxicity from taking vitamin D supplements is low - according to the US National Institutes of Health / Office of Dietary Supplements, ‘most reports suggest a toxicity threshold for vitamin D of 10,000-40,000 IU/day and serum 25(OH)D levels of 500–600 nmol/L (200-240 ng/mL)’ – whereas the potential benefits are huge.
The planned randomised controlled trial of vitamin supplementation to reduce the risk of covid-19 over winter will be a waste of time if inadequate doses are used – let’s hope that the ‘different vitamin D supplementation strategies’ includes some sensible doses such as suggested above
Competing interests: No competing interests