Over a year and a half into the Covid crisis, most of us have already heard about the link between vitamin D deficiency and the coronavirus. 

But while previous research mostly measured vitamin D levels once patients were already sick, a new Israeli study shows that even pre-infection vitamin D deficiency is associated with increased Covid-19 severity and mortality.

The study, conducted by researchers from Bar-Ilan University and its affiliate Galilee Medical Center, searched for vitamin D levels in the records of people with positive PCR tests for Covid who were admitted to the hospital between April 2020 and February 2021. It was recently published on MedRxiv  and is now being submitted to a peer-reviewed journal.

Dr. Amiel Dror. Photo by Tomasz Solinski

Of 1,176 patients admitted, 253 had vitamin D levels recorded 14 to 730 days prior to the positive test. Compared with mildly or moderately ill patients, those with severe or critical Covid were more likely to have severe pre-infection vitamin D deficiency, with levels less than 20 ng/mL.

“This study can highlight the risks of vitamin D deficiency in terms of Covid-19,” said Dr. Amiel Dror, who led the study. “Vitamin D is often associated with bone health. We’ve shown that it may also play an important role in other disease processes, such as infection.”

“It is still unclear why certain individuals suffer severe consequences of Covid-19 infection while others don’t,” added co-author Prof. Michael Edelstein. “Our finding adds a new dimension to solving this lingering puzzle.”

This does not necessarily mean that giving vitamin D to Covid patients will decrease the risk of severe disease, the researchers note. However, it does underscore the need to understand how to mitigate the effect of vitamin D deficiency.