Review the Research

Get summaries of key research on vitamin D and COVID-19

Vitamin D Deficiency Is Associated with COVID-19 Incidence and Disease Severity in Chinese People.

Take Home Message

Significantly lower serum 25(OH)D concentrations were found in severe COVID-19 patients from Wuhan, China compared to non-severe patients. Vitamin D deficiency (<30 nmol/L) was associated with COVID-19 severity, after adjusting for several potential confounders, such as age, sex, comorbidities, BMI and smoking status.


The aim of this study was to explore an association between the serum vitamin D level, obesity, and underlying health conditions, as well as the vulnerability to COVID‐19 in the Iranian population.


  • After adjusting for age, sex, comorbidities and BMI, serum 25(OH)D concentrations

were significantly lower among COVID-19 patients than the 2018–2019 controls (27.7 nmol/L vs. 31.8 nmol/L).

  • In the COVID-19 group, 261 (77.9%) patients were categorized as non-severe and 74 (22.1%) were categorized as severe. The severe COVID-19 patients were significantly

older and male (62.5 years, range 51.0-75.3 years; 58.1% male) than the non-severe COVID-19 patients (54.0 years, range 40.0–62.0 years; 40.2% male).

  • Statistical analysis (multivariate regression) showed that male sex, advanced age (≥65 y) and vitamin D deficiency (<30 nmol/L) were significantly associated with COVID-19 severity.


Three-hundred thirty-five consecutive patients diagnosed with COVID-19 who were admitted to Tongji Hospital (Wuhan, China) between February 27, 2020 and March 21, 2020.

Things to Keep in Mind

  • The cross-sectional study design may be a major limitation. Although vitamin D deficiency was associated with COVID-19 incidence and disease severity, causality cannot be established. Better-designed clinical trials are warranted in the future.
  • A sufficient number of vitamin D measurements could not be obtained from population wide testing during the study period (2020) due to the COVID-19 outbreak. Thus, the authors selected the 2018–2019 cohort as representative of the vitamin D status of the general public.
  • Since the study group was predominantly Asian, the results may not be applicable to populations with a significantly different ethnic makeup.


Author’s Conclusions

The study showed that individuals with vitamin D deficiency were more common among patients with COVID-19 infection and severe illness. Interventional trials

would be helpful in clarifying the role of vitamin D in COVID-19 infection and disease severity.

Study Design

  • A cross-sectional, retrospective study that analyzed 335 COVID-19 patients (median age =56.0 years; range=43.0–64.0 years) who were admitted to the Wuhan Tongji Hospital during the study period. Blood samples were obtained for all COVID-19 patients on admission and serum 25(OH)D concentrations were measured. Data regarding demographic characteristics, treatment, ventilation condition, and outcome were retrospectively reviewed from electronic medical records.
  • An age- and sex-matched population of 560 individuals (median age=55 years; range= 49.0–60.0 years) who underwent a physical exam during 2018-2019 and had serum 25(OH)D concentrations measured during the same period as the COVID-19 positive patients (27 February to 21 March) was used as a comparison.
  • Severity of COVID-19 was determined based on the level of respiratory involvement:
  • Mild: mild symptoms with no signs of pneumonia on imaging;
  • Moderate: fever, respiratory symptoms with radiological evidence of pneumonia;
  • Severe (meeting any of the following): respiratory distress, respiratory rate ≥30 breaths/min, hypoxemia, oxygen saturation (SpO2) ≤93% (at rest), or lung infiltrates of >50% within 24–48 h; and
  • Critical (meeting any of the following): respiratory failure requiring mechanical ventilation, shock, or multiple organ dysfunction requiring intensive care unit monitoring and treatment.
  • Mild and moderate cases were classified into the non-severe group, while severe and critical cases were classified into the severe group.
  • Patients were categorized as vitamin D–deficient (<30 nmol/L) or

non-vitamin D–deficient (≥30 nmol/L).

  • BMI was calculated as kg/m2.


Luo X, Liao Q, Shen Y, Li H, Cheng L. Vitamin D Deficiency Is Associated with COVID-19 Incidence and Disease Severity in Chinese People [corrected]. J Nutr. 2021 Jan 4;151(1):98-103. doi: 10.1093/jn/nxaa332. Erratum in: J Nutr. 2021 Mar 11;151(3):742-743. PMID: 33188401; PMCID: PMC7890671.

View Full Abstract

Research Summaries

Impact of daily high dose oral vitamin D therapy on the inflammatory markers in patients with COVID 19 disease

Impact of daily high dose oral vitamin D therapy on the inflammatory markers in patients with COVID 19 disease. Take Home Message In a prospective open-label interventional clinical trial in India