Let the sunshine in, at least in moderation. Vitamin D from the sun or from supplements is most often recognized for its role in bone health, but low levels of the supplement have been associated with a range of autoimmune, cardiovascular and infectious diseases. Early in the COVID-19 pandemic, health officials began to encourage people to take vitamin D, as it plays a role in promoting immune response and could help protect against COVID-19 along with vaccination.

In a study just published in the journal (US) Public Library of Science PLoS ONE, researchers at the Azrieli Faculty of Medicine of Bar-Ilan University (BIU) in Safed and the Galilee Medical Center (GMC) in Nahariya showed a correlation between vitamin D deficiency and COVID-19 severity and mortality. It was entitled “Pre-infection 25-hydroxyvitamin D3 levels and association with severity of COVID-19 illness.”  

Although there is plenty of sun in Israel and the rest of the Middle East, vitamin D deficiency is nevertheless a problem in Israel and many parts of the world. Epidemiological risk factors for vitamin D deficiency include greater skin pigmentation, low sun exposure, use of skin-covering clothes and a diet low in fish and dairy products. Studies have previously demonstrated that social habits in specific ethnic groups and a preference to wear long clothing outdoors are independent risk factors for vitamin D deficiency, particularly among women of some religions and ethnic backgrounds. 

The study is among the first to analyze vitamin D levels prior to infection. It facilitates a more accurate assessment than during hospitalization, when levels may be lower secondary to the viral illness. The findings reported build upon results initially published in the  MedRxiv, the preprint server for health sciences operated by Cold Spring Harbor Laboratory in New York. 

The records of 1,176 patients admitted between April 2020 and February 2021 to the GMC with positive PCR tests were searched for vitamin D levels measured two weeks to two years prior to infection. Patients with vitamin D deficiency (less than 20 ng/mL) were 14 times more likely to have a severe or critical case of COVID than those with more than 40 ng/mL. Strikingly, mortality among patients with sufficient vitamin D levels was 2.3%, in contrast to 25.6% in the vitamin D-deficient group.

The study adjusted for age, gender, season (summer/winter), chronic diseases and found similar results across the board – highlighting that low vitamin D level contributes significantly to disease severity and death.

“Our results suggest that it is advisable to maintain normal levels of vitamin D. This will be beneficial to those who contract the virus,” said Dr. Amiel Dror, of the GMC and BIU, who led the study. “There is a clear consensus for vitamin D supplementation on a regular basis as advised by local health authorities as well as global health organizations.” 

Dr. Amir Bashkin, an endocrinologist who participated in the new study, added that “this is especially true for the COVID-19 pandemic when adequate vitamin D has an added benefit for the proper immune response to respiratory illness.” 

“This study contributes to a continually evolving body of evidence suggesting that a patient’s history of vitamin D deficiency is a predictive risk factor associated with poorer COVID-19 clinical disease course and mortality, commented study co-author Prof. Michael Edelstein of BIU’s medical faculty. “It is still unclear why certain individuals suffer severe consequences of COVID-19 infection while others don’t. Our finding adds a new dimension to solving this puzzle.”