Vitamin D deficiency has been often associated with a range of autoimmune disorders, cardiovascular diseases, and even infectious diseases.

In the early stage of the pandemic, experts began to encourage people to start with vitamin D supplementation, as it plays a key role in boosting the immune system, potentially offering protection against COVID-19.

Now, a new study, published in the journal PLOS ONE, has shown a correlation between vitamin D deficiency and COVID severity and mortality, according to Science Daily.

The study analyzed vitamin D levels before COVID infection, facilitating a more accurate assessment than during hospitalization, when levels may be lower probably due to the viral illness.

Researchers looked at more than 1,170 patients hospitalized with COVID, between April 2020 and February 2021. The patients’ vitamin D levels were measured two weeks to two years before catching the virus.

The study found that patients with low vitamin D (less than 20 ng/mL) were 14 times more likely to have severe COVID illness than those with more than 40 ng/mL. The mortality rate among patients with sufficient vitamin D levels was 2.3%, while those with low vitamin D had a mortality rate of 25.6%.

Lead author Dr. Amiel Dror said, “Our results suggest that it is advisable to maintain normal levels of vitamin D. This will be beneficial to those who contract the virus. 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, who was part of the study, said, “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.”

The study’s co-author Prof. Michael Edelstein said, “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.”

“It is still unclear why certain individuals suffer severe consequences of COVID-19 infection while others don’t,” he added. “Our finding adds a new dimension to solving this puzzle.”