Changes in 25‐hydroxyvitamin D levels post‐vitamin D supplementation in people of Black and Asian ethnicities and its implications during COVID‐19 pandemic: A systematic review

Background: People of Black and Asian ethnicities have a higher infection rate and mortality as a result of COVID-19. It has also been reported that vitamin D deficiency may play a role in this, possibly because of the multi-gene regulatory function of the vitamin D receptor. As a result, increased dietary intake and/or supplementation to attain adequate 25-hydroxyvitamin D (25(OH)D) levels could benefit people in these ethnicities. The present study aimed to review the literature examining the changes in 25(OH)D in different types of vitamin D supplementation from randomised controlled trials in this population. Methods: This systematic review was conducted using the PRISMA guidelines. Electronic databases were systematically searched using keywords related to vitamin D supplementation in Black and Asian ethnicities. Results: Eight studies were included in the review. All the included studies found that supplementation of vitamin D (D2 and D3), regardless of dosage, increased 25(OH)D levels compared to a placebo. All trials in which participants were vitamin D deficient at baseline showed increased 25(OH)D levels to a level considered adequate. Two studies that used food fortification yielded smaller 25(OH)D increases compared to similar studies that used oral supplementation (10.2 vs. 25.5 nmol L−1, respectively). Furthermore, vitamin D2 supplementation yielded significantly lower 25(OH)D increases than vitamin D3 supplementation. Conclusions: Oral vitamin D supplementation may be more efficacious in increasing 25(OH)D levels than food fortification of Black and Asian ethnicities, with vitamin D3 supplementation possibly being more efficacious than vitamin D2. It is recommended that people with darker skin supplement their diet with vitamin D3 through oral tablet modes where possible, with recent literature suggesting a daily intake of 7000–10,000 IU to be potentially protective from unfavourable COVID-19 outcomes. As a result of the paucity of studies, these findings should be treated as exploratory