SynthesisNutrition journal2021
Low vitamin D levels do not aggravate COVID-19 risk or death, and vitamin D supplementation does not improve outcomes in hospitalized patients with COVID-19: a meta-analysis and GRADE assessment of cohort studies and RCTs.
Synthesis in Nutrition journal, 2021. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 43 papers, 4 of them syntheses that pooled it.
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
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Who cites it
43 citing papers in PubMed, 4 syntheses or guidelines pooled it, 104 citations in OpenAlex.
- Effect of the vitamin D supplementation on clinical outcomes and inflammatory status in COVID-19 patients: an umbrella review.BMC nutrition · 2025Pooled it
- The bounds of meta-analytics and an alternative method.Epidemiology and health · 2024Pooled it
- The impact of supplementing vitamin D through different methods on the prognosis of COVID-19 patients: a systematic review and meta-analysis.Frontiers in nutrition · 2024Pooled it
- Does vitamin D supplementation reduce COVID-19 severity?: a systematic review.QJM : monthly journal of the Association of Physicians · 2022Pooled it
- Evidence for the Efficacy of a High Dose of Vitamin D on the Hyperinflammation State in Moderate-to-Severe COVID-19 Patients: A Randomized Clinical Trial.Medicina (Kaunas, Lithuania) · 2022Trial
- Prevention of covid-19 and other acute respiratory infections with cod liver oil supplementation, a low dose vitamin D supplement: quadruple blinded, randomised placebo controlled trial.BMJ (Clinical research ed.) · 2022Trial
- Vitamin D in Infectious Diseases: A Narrative Review Focusing on COVID-19, Long COVID, and Influenza.Nutrients · 2026Review
- Reply to "Currently, no appropriately designed studies have demonstrated a link between vitamin D levels and coronavirus disease 2019 severity".Journal of the Chinese Medical Association : JCMA · 2026Article
- Currently, no appropriately designed studies have demonstrated a link between vitamin-D levels and COVID-19 severity.Journal of the Chinese Medical Association : JCMA · 2026Article
- Correlation between rs7041 and rs4588 polymorphisms in vitamin D binding protein gene and COVID-19-related severity and mortality.BMC medical genomics · 2024Article
- Retrospective Analysis of the Effect of Postmenopausal Women Medications on SARS-CoV-2 Infection Progression.Life (Basel, Switzerland) · 2024Article
- Is Serum 25-Hydroxyvitamin D Level Associated with Severity of COVID-19? A Retrospective Study.Journal of clinical medicine · 2023Article
- The Management of COVID-19-Related Coagulopathy: A Focus on the Challenges of Metabolic and Vascular Diseases.International journal of molecular sciences · 2023Review
- A Retrospective Analysis of Vitamin D Levels in Hospitalized COVID-19 Patients With Suspected Pulmonary Embolism.Cureus · 2023Article
- Hospital Outcomes in Patients Hospitalized for COVID-19 Pneumonia: The Effect of SARS-CoV-2 Vaccination and Vitamin D Status.Nutrients · 2023Article
- The Role of Diet and Specific Nutrients during the COVID-19 Pandemic: What Have We Learned over the Last Three Years?International journal of environmental research and public health · 2023Review
- 25 Hydroxyvitamin D Serum Concentration and COVID-19 Severity and Outcome-A Retrospective Survey in a Romanian Hospital.Nutrients · 2023Article
- COVID-19 and Multiple Sclerosis: A Complex Relationship Possibly Aggravated by Low Vitamin D Levels.Cells · 2023Review
- A Prospective Analysis of Vitamin D Levels in Pregnant Women Diagnosed with Gestational Hypertension after SARS-CoV-2 Infection.Journal of personalized medicine · 2023Article
- Vitamin D3 and COVID-19 Outcomes: An Umbrella Review of Systematic Reviews and Meta-Analyses.Antioxidants (Basel, Switzerland) · 2023Review
Corrections and comments
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Authors and funding
9 authors at 4 institutions in 2 countries.
Funding
Abstract
backgroundThe associations between vitamin D and coronavirus disease 2019 (COVID-19) infection and clinical outcomes are controversial. The efficacy of vitamin D supplementation in COVID-19 is also not clear.
methodsWe identified relevant cohort studies that assessed the relationship between vitamin D, COVID-19 infection and associated death and randomized controlled trials (RCTs) that reported vitamin D supplementation on the outcomes in patients with COVID-19 by searching the PubMed, EMBASE, and medRxiv databases up to June 5th, 2021. Evidence quality levels and recommendations were assessed using the GRADE system.
resultsEleven cohort studies with 536,105 patients and two RCTs were identified. Vitamin D deficiency (< 20 ng/ml) or insufficiency (< 30 ng/ml) was not associated with an significant increased risk of COVID-19 infection (OR for < 20 ng/ml: 1.61, 95% CI: 0.92-2.80, I2 = 92%) or in-hospital death (OR for < 20 ng/ml: 2.18, 95% CI: 0.91-5.26, I2 = 72%; OR for < 30 ng/ml: 3.07, 95% CI: 0.64-14.78, I2 = 66%). Each 10 ng/ml increase in serum vitamin D was not associated with a significant decreased risk of COVID-19 infection (OR: 0.92, 95% CI: 0.79-1.08, I2 = 98%) or death (OR: 0.65, 95% CI: 0.40-1.06, I2 = 79%). The overall quality of evidence (GRADE) for COVID-19 infection and associated death was very low. Vitamin D supplements did not significantly decrease death (OR: 0.57, I2 = 64%) or ICU admission (OR: 0.14, I2 = 90%) in patients with COVID-19. The level of evidence as qualified using GRADE was low.
conclusionsCurrent evidence suggested that vitamin D deficiency or insufficiency was not significantly linked to susceptibility to COVID-19 infection or its associated death. Vitamin D supplements did not significantly improve clinical outcomes in patients with COVID-19. The overall GRADE evidence quality was low, we suggest that vitamin D supplementation was not recommended for patients with COVID-19.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.