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

Take Home Message

In this small, case control study conducted in China there was an association between vitamin D deficiency and COVID-19, especially in severe cases.


  • Severe/critical cases were significantly older than mild/moderate cases (median: 65 vs 39 years).
  • The frequency of symptoms, such as fever (eight [80%]), cough (seven [70%]), and diarrhea (one [10%]), were higher in severe/critical COVID-19 cases than in mild/moderate cases (32 [64%], 24 [48%] and two [4%] respectively), but differences were not statistically significant.
  • There were higher rates of underlying conditions, including diabetes (two [20%]), hypertension (two [20%]), and renal failure (eight [80%]), in the severe/critical cases compared to mild/moderate cases (three [6%], four [8%], and eight [16%] respectively). Only renal failure showed statistical significance.
  • The serum 25(OH)D levels in COVID-19 patients (55.6 nmol/L) were statistically lower than in healthy controls (71.8 nmol/L).
  • 26 [41.9%] COVID-19 patients had VDD, while only 15 [18.8%] healthy individuals had VDD.
  • Results of multivariate regression analysis including all potential risk factors as independent variables (including VDD, age, sex, renal failure, diabetes, and hypertension) indicate a statistically significant association between VDD and severe/critical COVID-19 disease.
  • A potential threshold of 25(OH)D (41.19 nmol/L) to protect against COVID-19 was identified.


All (62) patients with COVID-19 disease, from February 16th, 2020 to March 16th, 2020, treated at the Yongwu Hospital of The People’s Hospital of Guangxi Zhuang Autonomous Region, Nanning, China, the largest designated hospital to provide care to patients with COVID-19 in Guangxi Province. The 62 patients were compared to 80 healthy matched controls.

Things to Keep in Mind

  • This study used a small sample size.
  • The subjects came from the same geographical region, an urban area of China making generalizability to other regions or ethnicities challenging.
  • The healthy controls were not tested for COVID-19 which means there may have been some who were positive for COVID-19, but asymptomatic, which could influence results.
  • Test subjects were all those who were tested in the hospital which may make generalizing to a population that never sought care in a hospital difficult.

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

  • The purpose of this case control study was to examine the association between 25(OH)D levels and COVID-19 disease, its severity, and its clinical characteristics in a Chinese population.
  • Serum 25(OH)D levels and rates of vitamin D deficiency (VDD) between 80 healthy controls (no COVID-19 diagnosis) and 62 patients diagnosed with COVID-19 and admitted to Guangxi People’s Hospital, China.
  • Cases were categorized into asymptomatic, mild/moderate, and severe/critical disease (no patients died during the study).
  • Logistic regression analysis was conducted to examine the associations between 25(OH)D level, or vitamin D deficiency (VDD), and case status/severity of COVID-19 while controlling for demographics and comorbidities.
  • A threshold level of vitamin D for conveying COVID-19 risk was estimated.


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. 2020 Oct 13:1-8. doi: 10.1080/07315724.2020.1826005. Epub ahead of print. PMID: 33048028.

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