Vitamin D and its protective effect against COVID-19: why low levels predispose to disease

The global pandemic caused by infection with the SARS-CoV-2 virus has affected people from all walks of life since it emerged in China in December 2019. Worldwide, millions of people have been infected with the virus and died, and as experts have noted, the spread of COVID-19 infection was particularly high among African Americans, who tend to live in dense, low-income communities and work in occupations where they are. more likely to be exposed to the virus. .

Now, several recent studies examined the role of vitamin D levels in relation to COVID-19 infection. And some of them found a higher incidence of infection in people with lower levels of vitamin D.

Vitamin D is a natural hormone that regulates mineral and skeletal homeostasis and modulates the innate immune system. In humans, vitamin D is obtained from the diet in the form of ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3) derived from plants, yeasts and fungi, or via food supplements. Another important source is exposure to ultraviolet B radiation, which is involved in the conversion of 7-dehydrocholesterol to vitamin D3 by the liver.

The nutrient is essential for healthy bones at all stages of life, from fetal development to old age because of the role it plays in calcium homeostasis (skeletal or classic actions). In recent years, it has been reported that vitamin D also participates in the regulation of many tissues and organs through so-called extra-skeletal or unclassical actions of vitamin D.

“Coronaviruses belong to a large family of viruses (coronaviridae) which infect birds and various mammals. The coronavirus, currently known as SARS-CoV-2, was discovered in December 2019 in Wuhan, Hubei province, China, and is the causative agent of the current atypical pneumonia epidemic. With this introduction, Argentinian researchers Mariana Seijo and Beatriz Oliveri del Conicet showed that “the most severe cases present with acute respiratory distress syndrome which can lead to death” and pointed out that “vitamin D (VD), In addition to the well-known and positive effect on bone health and calcium homeostasis, it has a pleiotropic effect on various organs, with an almost universal distribution of the RV receptor and enzymes metabolizing 25-hydroxyvitamin D (25OHD ) in the cells of the body.. These extra-skeletal actions depend on the synthesis in these cells of the active metabolite 1,25 dihydroxyvitamin D by paracrine and autocrine regulation, dependent on the optimal circulating levels of 25OHD ”.

Due to its immunomodulatory, anti-inflammatory, antimicrobial, regulatory actions of the renin-angiotensin-aldosterone system, promoting the compensation of the respiratory epithelium and cellular redox homeostasis, vitamin D may have a protective effect in infection. COVID-19.

Precisely, “among the groups at risk of COVID-19 are the elderly, obese, diabetic, hypertensive, with cardiovascular diseases, pathologies with a higher incidence in individuals with hypovitaminosis with RV”, underlined the experts. . RV supplementation, to achieve optimal 25OHD levels of 40-60 ng / ml, could reduce the incidence, severity and risk of death in the current COVID-19 pandemic, as a complementary measure while the vaccine and other specific drugs are under development.

Now, in addition, a recent study from Boston University has shown that “black Americans often suffer from insufficiency (25 (OH) D) (20-29 ng / ml; 50-72.5 nmol / l) or deficiency (<20 ng / ml; <50 nmol / l), largely due to the darker pigmentation of the skin resulting in less penetration of sunlight and subsequent production of vitamin D. ".

“Once infected with COVID-19, black women are particularly vulnerable to developing serious illness, in part due to high levels of predisposing conditions such as hypertension, type 2 diabetes and obesity. the researchers pointed out. Given the overrepresentation of black women among COVID-19 cases and deaths and the high levels of 25 (OH) D insufficiency in black women, it is particularly important to assess the relationship between serum concentrations of 25 (OH) D and the risk of COVID infection. -19 in this population group ”.

Among 5,081 study participants whose blood sample had been tested for 25 (OH) D, 1,974 reported having been tested for COVID-19 in 2020. Compared to women with levels of 25 (OH ) D of 30 ng / mL (75 nmol / L) or more, multivariate adjusted ORs for COVID-19 infection in women with levels of 20 to 29 ng / ml (50 to 72.5 nmol / L ) and <20 ng / ml (<50 nmol / L) were, respectively, 1.48 (95% CI 0.95 to 2.30) and 1.69 (95% CI 1.04 to 2, 72) (trend p 0.02).

Study results suggest that black American women with lower 25 (OH) D levels are at increased risk of COVID-19 infection, although they recognize that more work is needed to confirm these results and determine the optimal level of 25 (OH) D for a beneficial effect.

KEEP READING