Vitamin D, the fat-soluble hormone produced in the body when sunlight hits the skin, is responsible not only for bone health but is also believed to help regulate the immune and neuromuscular systems. Vitamin D deficiency has been linked to breast cancer, colon cancer, prostate cancer, heart disease, depression, weight gain and other maladies.1
Research on Vitamin D has exploded in the last ten years, and not only is there a large and growing literature on Vitamin D’s role in reducing the risk of acute respiratory infections and reducing morbidity and mortality in critical care settings,2 but new research confirms a relationship between vitamin D levels and the respiratory illness believed to be caused by the novel coronavirus SARS CoV-2.3 4 5 6 7 8 9
Vitamin D levels correlated with health outcomes in COVID-19 patients
In a study10 published on May 6, researchers reviewed data from 20 European countries. Vitamin D levels are severely low in some aging populations, especially in Spain, Italy and Switzerland, whereas Vitamin D levels were higher in the Nordic countries. The study found a negative correlation between mean levels of Vitamin D and number of cases of COVID-19 and mortality from the new coronavirus.
The authors suggested that Southern European countries have lower levels of vitamin D because of decreased exposure to the sun (because people prefer the shade) and darker skin pigmentation, which decreases Vitamin D synthesis. Northern Europe’s levels are better due to the consumption of cod liver oil, vitamin supplements, and Vitamin D fortification of milk and milk products. Furthermore, they suggested that Vitamin D has a modulating effect on inflammatory cytokines, chemokines, and ACE2, which protects against lung injury.
A small, retrospective observational study11 conducted at Louisiana State University Health Sciences Center found the baseline prevalence of Vitamin D insufficiency (VDI) among ICU patients hospitalized in the intensive care unit (ICU) for any cause is 30 to 40 percent, whereas for patients in ICU units with COVID-19, 84.6 percent had VDI. This is in contrast to only 57.1 percent of the COVID-19 patients hospitalized on general floors testing positive for Vitamin D insufficiency.
Strikingly, 100 percent of ICU patients less than 75 years old had Vitamin D insufficiency. Authors of this study believe their findings also contribute to understanding the racial aspect of health disparities associated with COVID-19 hospitalization and mortality statistics. VDI is highly prevalent in dark-skinned persons: 82.1 percent of African Americans have Vitamin D insufficiency vs. 41.6 percent in the U.S. general population.
In a retrospective study12 of 212 COVID-19 patients in the Philippines published electronically on April 9, 2020, Vitamin D status was significantly associated with severity of COVID-19. In the analysis, 85.5 percent of patients with sufficient Vitamin D had mild cases while 72.8 percent of patients who were deficient in Vitamin D had severe or critical cases.
A retrospective cohort study13 of 780 cases with laboratory-confirmed infection of SARS-CoV-2 in Indonesia revealed that a majority of the death cases were older males with pre-existing conditions and Vitamin D insufficiency. Patients with Vitamin D insufficiency (between 20 and 30 ng/ml) were 12.55 times more likely to die and patients with severe Vitamin D deficiency (<20 ng/ml) were 19.12 times more likely to die than those patients with sufficient levels of Vitamin D. After controlling for age, sex, and comorbidity, Vitamin D status is strongly associated with COVID-19 mortality. When compared to COVID-19 cases with normal Vitamin D status, death was approximately 10.12 times more likely for Vitamin D deficient cases.