Study Links Vitamin D Deficiency to Incidence and Worsened COVID-19 Outcomes

01.11.21

A recent study in China showed that vitamin D deficiency was among significant risk factors for COVID-19 severity.

Since the onset of the COVID-19 pandemic, epidemiological studies have been in place in an attempt to identify which nutrient deficiencies may play a role in the incidence or severity of the virus. Growing observational data, which has yet to establish conclusive evidence regarding efficacy, links vitamin D deficiency to elevated incidences of severe COVID-19 outcomes, including a recently-published study appearing in the Journal of Clinical Nutrition.
 
Vitamin D deficiency, most often attributed to a lack of sunlight exposure, affects almost 1 billion people worldwide, the authors of the study said. Likewise, it has been identified as a risk factor for incidence and severity of a number of respiratory tract infections.   
 
A cross-sectional study retrospectively analyzed 335 COVID-19 patients who were admitted to the Wuhan Tongji Hospital between February and March of last year, who were cross-referenced with an age- and sex-matched population of 560 people who underwent the physical examination program, whose serum vitamin D concentrations were measured in 2018-2019. The serum vitamin D concentrations of the COVID-19 patients were measured upon admission to the hospital.
 
It was determined that in the COVID-19 group, 77.9% of patients had non-severe cases of the disease, while the remaining 22.1% were categorized as severe. Researchers found that there were no significant differences between the severe and non-severe groups in BMI distribution and smoking status. In total, 29.7% of patients received corticosteroid treatment, and 21.6% received ventilation assistance (5 noninvasive and 11 invasive ventilations).
 
In total, 82.4% of the severe COVID-19 patients, and only 60.2% of the non-severe COVID-19 patients were vitamin D deficient, though vitamin D deficiency did not affect the length of the hospital stays following analysis.
 
The severity of COVID-19 cases was determined based on the level of respiratory involvement for each patient’s treatment. Among other risk factors, such as male sex and older age, vitamin D deficiency was significantly associated with COVID-19 severity, along with other well-known issues such as comorbidities and BMI.
 
“However, this cross-sectional analysis does not allow us to draw conclusions regarding causality, and more research is needed. Overall, evidence suggests that vitamin D could be an etiological factor in COVID-19 infection,” the authors said. They project that vitamin D’s role in the functions of innate immunity, such as barrier integrity, enzyme expressions, and other immune system and inflammatory modulations could play a role in the beneficial association.