Because vitamin D deficiency has been associated with severe forms of COVID-19, several scientific publications have highlighted its benefits in preventing the disease. However, these are controversial and solid proofs are still lacking.
Vitamin D is essential for good health and is synthesized by the skin during sun exposure or supplied through food or supplements. In winter, sun exposure decreases and can cause a vitamin D deficiency, especially in northern European countries. Additionally, several hypotheses link vitamin D deficiency to upper respiratory tract diseases such as colds and influenza, which are ubiquitous in winter.
These conclusions remain controversial, but have found a new echo with the COVID-19 epidemic. In April, a U.S. publication suggested that patients with vitamin D deficiency were twice as likely to get a severe form of COVID-19. So, is vitamin D necessary to prevent or cure COVID-19?
A brief report, written by a group of English researchers from several universities and published in BMJ Nutrition Prevention and Health, provides an overview of the current scientific evidence on vitamin D and COVID-19. The report notes that the effects of vitamin D on disease are poorly documented and that taking extra vitamin D is not without risk.
The report of the English scientists mentions the publication of several questionable studies highlighting the benefits of vitamin D as a preventive treatment for COVID-19 or influenza. One of them was supported by a pharmaceutical company that sells vitamin D, another is no longer available in the virtual library of scientific literature Pubmed.
Therefore, there is currently no strong evidence of the effects of vitamin D in COVID-19, and clinical trials are just being conducted in China to investigate this issue.
Do not exceed the maximum daily dose
The maximum recommended dose for adults is 4,000 IU of vitamin D per day. One of the biased studies recommends taking up to 10,000 IU of vitamin D per day for a few days. Although cases are rare, taking that dose without medical advice and without a proven deficiency can be harmful, especially to the kidneys, causing hypercalcemia.
Pending solid scientific results on the effect of vitamin D on COVID-19, scientists advise not to exceed the maximum daily dose.