Experts Caution Against High Doses of Vitamin D for COVID-19

High doses of vitamin D supplement have not shown any benefit in preventing or treating coronavirus disease 2019 (COVID-19), and individuals should be cautioned against over supplementation of the vitamin, experts emphasized in a global consensus paper published in BMJ, Nutrition, Prevention and Health.¹

Unverified reports have suggested that of high-dose vitamin D (higher than 4000IU/d) could reduce the risk of COVID-19; however, there is currently not enough scientific evidence to back these claims.

For the paper, a team of experts led by the University of Surrey analyzed previous studies to determine whether there was evidence of a link between high-dose vitamin D supplementation and successful prevention or treatment of COVID-19. The investigators also examined whether vitamin D levels were associated with respiratory tract infections.

Findings from a majority of the studies in the review were based on data gathered from population groups in developing countries and cannot be extrapolated to populations from more developed countries due to external factors, the investigators said.

“As a key micronutrient, vitamin D should be given particular focus–not as a ‘magic bullet’ to beat COVID-19, as the scientific evidence base is severely lacking at this time–but rather as part of a healthy lifestyle strategy to ensure that populations are nutritionally in the best possible place,” the investigators wrote.

According to the investigators, the current pandemic has led to calls for widespread high-dose vitamin D supplementation; calls that are without support from pertinent studies in humans at this time. Instead, many of these claims are based on speculations about presumed mechanisms, with no clear evidence of benefit.

They noted that 2 key studies support this presumption:

1. An unbiased screen of repurposed drugs for treatment of avian influenza A H5N1 virus using appropriate cell lines and mice, which highlighted calcitriol as a potential therapy.

2. A recent analysis of vitamin D and viral infections.

However, it is still unknown whether these mechanisms apply to COVID-19.

Based on these results, the investigators determined that further research is justified, but they “strongly caution against doses higher than the upper limit (4000IU/day; 100 µg/day); and certainly of very high doses of vitamin D (in some reports, 10,000 IU/day [250 µg/day] of vitamin D are being promoted) unless under personal medical advice/clinical advice by a qualified health professional.”

Although vitamin D supplementation is encouraged for individuals who may be deficient, especially those who are currently self-isolating with limited access to sunlight, supplementation guidance should be followed.

“Levels of the vitamin in the body can also be supplemented through a nutritionally balanced diet including foods that provide the vitamin, such as oily fish, red meat, egg yolk, and fortified foods such as breakfast cereals, and safe sunlight exposure to boost vitamin D status,” paper co-author Judy Buttriss, director general of the British Nutrition Foundation, said in a press release.²

References:

1. Lanham-New SA, Webb AR, Cashman KD, et al. Vitamin D and SARS-CoV-2 virus/COVID-19 disease. BMJ Nutrition, Prevention & Health. 2020. http://dx.doi.org/10.1136/bmjnph-2020-000089

2. High doses of vitamin D supplementation has no current benefit in prevention or treating Covid-19. News Release. University of Surrey; May 21, 2020. Accessed May 26, 2020. https://www.surrey.ac.uk/news/high-doses-vitamin-d-supplementation-has-no-current-benefit-preventing-or-treating-covid-19