As evidence builds that COVID-19 patients with vitamin D deficiency are more likely to experience severe clinical outcomes (ICU risk is 20-fold greater, international data suggests), urgent trials are underway to evaluate whether vitamin D could be used to treat or prevent the disease.
In April two studies by researchers in Ireland drew international attention by highlighting vitamin D’s potential role in priming the body’s defences against COVID-19. The researchers, part of the TILDA study group, described vitamin D ‘as a potent immune modifying micronutrient’ and suggested that, at sufficient levels, it could play an important role in protecting vulnerable adults, particularly those who are obese or have pre-existing lung conditions – both groups among those known to be more susceptible to complications.
Findings in Europe and North America that black, Asian and minority ethnic groups are disproportionately affected by COVID-19, and more likely to die from it, raised further questions about vitamin D’s role. While socio-economic factors are likely to contribute, there is mounting concern that poorer absorption of vitamin D from sunlight in people with darker skin may play an important role.
Similarly, elderly and other institutionalized groups may be more susceptible to serious complications from COVID-19 due to poor vitamin D status. The problem is likely to have been compounded by the lockdown itself, which may have shifted larger parts of the population – who have spent months indoors – to an at-risk status.
While the high death rates seen in Italy and Spain might seem to weaken the logic beyond the vitamin D-COVID-19 outcome connection, vitamin D awareness and supplementation are low in southern Europe (in contrast to, say, Nordic countries where supplementation and fortification is common, or even mandated, and where death rates have been much lower).
Urgent studies are now being carried out in France, Spain and the US.