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Does Serum Vitamin D Level Affect COVID-19 Infection and Its Severity?-A Case-Control Study

Take Home Message

Vitamin D deficiency and obesity increases risk of testing positive for COVID-19.


  • Vitamin D levels in COVID-19 patients were lower than in health controls (55.6nmol/L vs. 71.8 nmol/L, respectively.)
  • 9% of COVID patients had vitamin D deficiency compared to 18.8% in health individuals.
  • Vitamin D levels in severe COVID-19 cases were significantly lower than mild cases (38.2nmol/L vs. 56.6nmol/L)
  • The vitamin D value that determined threshold for predicting severity of illness was 41.19nmol/L


62 Patients with COVID-19 from February 16,2020 through March 16, 2020 treated at Yongwu Hospital

Things to Keep in Mind

  • Excessive autoimmune dysregulation may contribute to COVID-19
  • Recommendations to achieve a level >50nmol/L is 800IU/d but remains to be clear on the effectiveness on COVID-19 infection.
  • This study had low power which means that it may not have been able to detect difference in some clinical symptoms and indicators.
  • Findings might not generalize to all populations as the majority of the COVID-19 population studied were from urban areas.
  • Vitamin D levels were only assessed after admission and the onset of COVID-19 symptoms, but due to vitamin D being stable against acute respiratory infection, the levels at testing may be valid to determine levels prior to infection.

Author’s Conclusions

Elderly and people with comorbidities were susceptible to severe COVID-19 infection. VDD was a risk factor for COVID-19, especially for severe/critical cases. While further confirmation is needed, vitamin D supplementation may have prevention or treatment potential for COVID-19 disease.

Study Design

  • Case-control study that examined sex, age, clinical variables and symptoms (fever, cough, chest tightness, chest pain, and diarrhea,) and comorbidities (hypertension, diabetes, COPD, asthma, liver injury, and renal failure)
  • Vitamin D levels were definded as follows: deficiency <50nmol/L; insufficiency <75nmol/L, and sufficiency ≥75nmol/L



Ye K, Tang F, Liao X, Shaw BA, Deng M, Huang G, Qin Z, Peng X, Xiao H, Chen C, Liu X, Ning L, Wang B, Tang N, Li M, Xu F, Lin S, Yang J. Does Serum Vitamin D Level Affect COVID-19 Infection and Its Severity?-A Case-Control Study. J Am Coll Nutr. 2021 Nov-Dec;40(8):724-731. doi: 10.1080/07315724.2020.1826005. Epub 2020 Oct 13. PMID: 33048028.

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