Vitamin C for COVID-19: real-time analysis of 177 studies

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Vitamin C for COVID-19

72 studies with >80,000 patients

Serious outcome risk

Vitamin C

Control

Significantly lower risk for mortality, ICU, hospitalization, and recovery.

20% lower risk in 20 RCTs CI 8-31%

COVID-19 Vitamin C studies · October 2026

Outcome (studies)

Improvement

Relative risk · 95% CI

All studies (72)21%

With exclusions (42)25%

Mortality (44)19%

Hospitalization (16)19%

Recovery (10)29%

Cases (7)3%

Viral clearance (2)−5%

RCTs (20)20%

RCT mortality (14)14%

High-dose IV (23)22%

Prophylaxis (17)19%

Early (6)34%

Late (49)21%

00.511.5+

← Vitamin C
reduces riskIncreased
risk →

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The European Food Safety Authority has found evidence for a causal relationship between the intake of vitamin C and optimal immune system function1,2. High doses may increase the risk of kidney stones3, with risk depending on formulation, predisposition, diet, and hydration4. Choi et al. show the highest bioavailability from fruit and vegetable juice compared with raw fruit and vegetables and vitamin C treatment, with the lowest bioavailability from vitamin C treatment. Vitamin C was adopted in 22 countries. Recent:

Hamza

Hosseini

Younes

Adetunji.


	Covid Analysis	Vitamin C reduces COVID-19 risk: real-time meta-analysis of 72 studies (Version 88)
	Significantly lower risk is seen for mortality, ICU admission, hospitalization, and recovery. 25 studies from 25 independent teams in 12 countries show significant benefit. Meta-analysis using the most serious outcome reported shows..
Aug 26	Hosseini et al., medRxiv, doi:10.64898/2026.08.21.26360704	Efficacy of antioxidant therapy in mild to moderate SARS-CoV-2 infection: A pilot experimental arm of the CanTreatCOVID adaptive platform trial
	52% lower hospitalization (p=0.38) and 42% improved recovery (p=0.13). RCT 81 outpatients showing ~2-3x higher odds of favorable recovery outcomes with antioxidant treatment (selenium 300 µg, zinc 40 mg, lycopene 45 mg, vitamin C 1.5 g). With 81 patients the trial is too small to reach statistical significan..
Jun 30	Hamza et al., International Journal of Nutrology, doi:10.54448/ijn26227	Estimation of oxidative stress, antioxidants and trace elements for COVID-19 patients: a cross-sectional study
	Cross-sectional study of 60 COVID-19 patients and 40 healthy controls showing significant oxidative stress imbalance, with elevated copper and total oxidant status, and decreased selenium and vitamin C levels in COVID-19 patients compared..
Apr 8	Younes, S., Next Research, doi:10.1016/j.nexres.2026.101727	The influence of micronutrients on olfactory dysfunction associated with COVID-19 and long COVID
	Review of the influence of micronutrients on olfactory dysfunction associated with COVID-19 and long COVID. Author investigates how dietary supplements like vitamins A, B, C, D, E, zinc, and alpha-lipoic acid can help restore the sense of..
Feb 28	Adetunji et al., BMC Infectious Diseases, doi:10.1186/s12879-026-12959-7	Association between serum vitamins and COVID-19 infection: a cross-sectional study of healthcare workers in a Nigerian tertiary hospital
	Cross-sectional study of 181 healthcare workers showing significantly lower serum levels of most vitamins (A, C, D, E, and B-complex vitamins except B12) in those with COVID-19 infection compared to uninfected controls. Authors hypothesiz..
Feb 16	McLindon et al., American Journal of Therapeutics, doi:10.1097/MJT.0000000000002118	Safety and Tolerability of Multimodal Therapy (Ivermectin, Doxycycline, Vitamin C, Vitamin D, and Zinc) With or Without Famotidine in Australian Patients With COVID-19 Infection: A Pilot Cohort Trial
	RCT 275 outpatients showing very low hospitalization with combination therapy including ivermectin, doxycycline, vitamin C, vitamin D3, and zinc, with or without famotidine. There was no control group. Only 4 patients were hospitalized wi..
Oct 23 2025	Choi et al., Nutrients, doi:10.3390/nu17213331	Comparative Bioavailability of Vitamin C After Short-Term Consumption of Raw Fruits and Vegetables and Their Juices: A Randomized Crossover Study
	Randomized crossover trial showing vitamin C bioavailability from supplements, raw fruits and vegetables, and fruit and vegetable juices in 12 healthy adults. Authors found that fruit and vegetable juice provided the highest plasma vitami..
Oct 7 2025	Adhora et al., Discover Social Science and Health, doi:10.1007/s44155-025-00303-4	The role of diet and micronutrient supplementation in COVID-19 recovery: a cross-sectional survey of Bangladeshi patients
	Retrospective 384 COVID-19 patients in Bangladesh showing shorter recovery time associated with the use of vitamin C, D, and zinc, balanced diet intake, and normal BMI.
Aug 15 2025	El Maakoul et al., The Egyptian Journal of Internal Medicine, doi:10.1186/s43162-025-00505-x	Mortality related to COVID-19 in kidney transplant recipients, dialysis patients and patients with chronic kidney disease: a cohort study
	Retrospective 250 COVID-19 patients with chronic kidney disease. Authors note in the abstract that azithromycin and vitamin C were associated with better outcomes, however no details are provided in the paper.
Jul 31 2025	Hazan et al., American Journal of Infectious Diseases, doi:10.3844/ajidsp.2026.4.26 (date from preprint)	Rapid Recovery of Peripheral Oxygen Saturation in Hypoxic COVID-19 Patients With Ivermectin/Doxycycline/Zinc Multidrug Therapy
	Retrospective 26 consecutive severe COVID-19 outpatients with hypoxia (25 with SpO₂ ≤90%) showing rapid oxygen saturation recovery and survival with ivermectin/doxycycline/zinc/vitamin C/vitamin D combination therapy. All 24 patients comp..
Jul 29 2025	Sharafi et al., Scientific Reports, doi:10.1038/s41598-025-91154-1	Exploring the influence of vitamin C concentrations on the dynamics of RT-PCR assay reactions
	In vitro study showing that vitamin C may interfere with COVID-19 RT-PCR diagnostics by altering reaction kinetics. High vitamin C concentrations (50-100 mg/ml) significantly increased Ct values in samples with high viral load while decre..
Jul 22 2025	Paul Jackson, C., Zenodo, doi:10.5281/zenodo.16325841	Micronutrientes esenciales en la evolución clínica del SARS-CoV-2 en pacientes hospitalizados
	Observational study of 15 hospitalized COVID-19 patients in Peru showing significant inverse correlations between the intake of zinc, selenium, and vitamin C with both lung damage and oxygen requirements.
Jul 15 2025	Al-Khrasani et al., Biomedicine & Pharmacotherapy, doi:10.1016/j.biopha.2025.118346	Do vitamins halt the COVID-19-evoked pro-inflammatory cytokines involved in the development of neuropathic pain?
	Review of vitamin supplementation for COVID-19-evoked pro-inflammatory cytokines involved in neuropathic pain development. Authors examine how certain vitamins may help prevent post-COVID neuropathic pain by modulating pro-inflammatory cy..
May 14 2025	Bepouka et al., Infection and Drug Resistance, doi:10.2147/IDR.S499371	Clinical Characteristics and Mortality Trends Among COVID-19 Patients During the First Four Waves in Ngaliema Clinic, Democratic Republic of the Congo
	76% lower mortality (p=0.01). Retrospective 410 hospitalized COVID-19 patients in the Democratic Republic of Congo showing significantly lower mortality with vitamin C treatment.
Apr 28 2025	Najimi et al., ChemistrySelect, doi:10.1002/slct.202406035	Phytochemical Inhibitors of SARS‐CoV‐2 Entry: Targeting the ACE2‐RBD Interaction with l‐Tartaric Acid, l‐Ascorbic Acid, and Curcuma longa Extract
	In vitro and in silico study showing that l-tartaric acid, l-ascorbic acid, and Curcuma longa extract (curcumin, demethoxycurcumin, bisdemethoxycurcumin) inhibit the SARS-CoV-2 spike RBD interaction with human ACE2. Authors demonstrate by..
Mar 25 2025	Gkioulekas et al., The Japanese Journal of Antibiotics, doi:10.11553/antibiotics.78.1_35	Critical appraisal of multidrug therapy in the ambulatory management of patients with COVID-19 and hypoxemia Part II: Causal inference using the Bradford Hill criteria
	Critical appraisal of three case series totaling 119 COVID-19 patients with hypoxemia treated with ivermectin-based multidrug protocols in the United States, Zimbabwe, and Nigeria, showing reduced hospitalization and mortality. Authors ap..
Mar 25 2025	Gkioulekas, Ph.D. et al., The Japanese Journal of Antibiotics, doi:10.11553/antibiotics.78.1_2	Critical appraisal of multidrug therapy in the ambulatory management of patients with COVID-19 and hypoxemia Part I. Evidence supporting the strength of association
	Critical appraisal of 119 COVID-19 hypoxemic patients treated with ivermectin-based multidrug protocols in the United States, Zimbabwe, and Nigeria, showing significant hospitalization rate reduction and mortality rate reduction compared ..
Mar 14 2025	Brandão et al., Frontiers in Nutrition, doi:10.3389/fnut.2025.1549747	Vaccination and food consumption: association with Post-Acute COVID-19 Syndrome in Brazilian adults (CUME Study)
	22% lower long COVID (p=0.01). Analysis of 2,065 Brazilian adults participating in the CUME study showing that higher intake of vitamin C, vitamin D, zinc, white meat, and vegetables were associated with lower risk of long COVID.
Mar 4 2025	Kafeshani et al., Journal of Health System Research, doi:10.48305/jhsr.v21i1.1579	Investigating the Relationship between Food Intake and Severity of COVID-19 Disease: A Cross-Sectional Study
	Cross-sectional study of 3,018 hospitalized (moderate and severe) and 717 outpatient (mild) COVID-19 patients showing differences in nutritional intake associated with disease severity. Patients requiring hospitalization had significantly..
Feb 20 2025	Rajamanickam et al., Journal of Pharmacy and Pharmacology Research, doi:10.26502/fjppr.0105	Exploring the Potential of Siddha Formulation MilagaiKudineer-Derived Phytotherapeutics Against SARS-CoV-2: An In-Silico Investigation for Antiviral Intervention
	In silico computational docking study of phytochemicals from MilagaiKudineer, showing potential inhibitory activity against SARS-CoV-2 targets. Authors evaluated binding affinities for the spike glycoprotein receptor-binding domain, RNA-d..
Jan 16 2025	Sanduzzi Zamparelli et al., Life, doi:10.3390/life15010113	Immune-Boosting and Antiviral Effects of Antioxidants in COVID-19 Pneumonia: A Therapeutic Perspective
	Review of immune-boosting and antiviral effects of antioxidants in COVID-19 pneumonia. Authors provide an overview of the literature on the use of antioxidants, including vitamins, trace elements, ozone, glutathione, L-carnitine, melatoni..
Jan 13 2025	Hemilä et al., Polish Archives of Internal Medicine, doi:10.20452/pamw.16926	Vitamin C for the common cold and pneumonia
	Review of vitamin C for the common cold and pneumonia. Authors conclude that while regular vitamin C supplementation does not prevent common colds infections in the general population, it significantly reduces the severity and duration of..
Jan 9 2025	Williams, R., Cureus, doi:10.7759/cureus.77188	COVID-19 Humic/Fulvic Acid Plus Epigallocatechin Gallate Treatment: A Retrospective Chart Review
	97% lower mortality (p<0.0001). Retrospective 60 COVID-19 patients in a nursing home facility showing no mortality with EGCG (from green tea extract), humic/fulvic acid, and vitamin C treatment, compared to 55% mortality in the control group not receiving treatment. The..
Feb 20 2025	Dinoi et al., Biomedicines, doi:10.3390/biomedicines13030535 (date from preprint)	Retrospective Clinical Investigation into the Association Between Abnormal Blood Clotting, Oral Anticoagulant Therapy, and Medium-Term Mortality in a Cohort of COVID-19 Patients
	32% higher mortality (p=0.3). Retrospective 247 non-survivors and 247 matched survivors in hospitalized COVID-19 patients in Italy showing results for several treatments.
Nov 18 2024	Pashaei et al., Journal of Comprehensive Pediatrics, doi:10.5812/jcp-149127	The Association Between COVID-19 Infection Severity and Micronutrient Deficiencies in Children
	21% lower severe cases (p=0.53). Analysis of 85 pediatric patients (33 healthy controls, 25 mild COVID-19, 27 severe COVID-19), showing significantly lower serum zinc levels in severe COVID-19 patients compared to healthy controls. Severe cases had higher prevalence of z..
Nov 13 2024	Uz et al., Inflammopharmacology, doi:10.1007/s10787-024-01597-7	Role of intravenous vitamin C on outcomes in hospitalized patients with moderate or severe COVID-19: a real life data of Turkish patients
	84% lower mortality (p=0.05). Retrospective 270 moderate/severe hospitalized COVID-19 patients, showing lower mortality with high (25 g/day) or low-dose (2 g/day) intraveneous vitamin C.
Nov 11 2024	Fazli et al., Journal of Medical Bacteriology, 12:4	Possible Link between Gut Microbiota, Diet, and COVID-19 Infection
	Review of the relationship between gut microbiota, diet, and COVID-19 infection. Authors analyze how SARS-CoV-2 infection affects gut microbiota composition and how dietary factors may influence disease outcomes. Studies show COVID-19 pat..
Nov 11 2024	Qin et al., Nutrition Reviews, doi:10.1093/nutrit/nuae154	Effects of Vitamin C Supplements on Clinical Outcomes and Hospitalization Duration for Patients with Coronavirus Disease 2019 (COVID-19): A Systematic Review and Meta-Analysis
	36% lower mortality (p=0.0001) and 41% lower severe cases (p=0.0006). Meta analysis of 22 studies with 6,831 patients showing significantly lower COVID-19 mortality and severity with vitamin C treatment.
Nov 8 2024	Xie et al., Cellular & Molecular Biology Letters, doi:10.1186/s11658-024-00659-6	The role of reactive oxygen species in severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) infection-induced cell death
	Review of the effects of reactive oxygen species (ROS) on cell death pathways in SARS-CoV-2 infection. SARS-CoV-2 induces oxidative stress and ROS generation which can lead to several types of regulated cell death including NETosis, ferro..
Oct 5 2024	Anber et al., Reports of Biochemistry & Molecular Biology, 13:2	Assessment of Oxidative Stress Parameters in Iraqi Male Patients with Covid-19; A Case Control Study
	Analysis of 50 symptomatic COVID-19 patients (25 ICU and 25 non-ICU) and 25 healthy controls, showing significantly lower vitamin C, zinc, and selenium levels in COVID-19 patients versus healthy controls, and in ICU patients versus non-IC..
Sep 24 2024	Grosman-Dziewiszek et al., Nutrients, doi:10.3390/nu16193225	Patterns of Dietary Supplement Use during the COVID-19 Pandemic in Poland: Focus on Vitamin D and Magnesium
	Survey of 926 Polish pharmacy patients showing a high prevalence of dietary supplemention during the COVID-19 pandemic, with vitamin D and magnesium being the most commonly used. Supplement use was significantly higher among women, those ..
Sep 18 2024	Kaushal, A., Journal of Translational Medicine, doi:10.1186/s12967-024-05587-9	Nutraceuticals and pharmacological to balance the transitional microbiome to extend immunity during COVID-19 and other viral infections
	Review of nutraceuticals and pharmacological interventions to balance the microbiome and boost immunity during COVID-19 and other viral infections. Authors propose that optimal usage of probiotics, dietary fibers, vitamins, minerals, omeg..
Sep 16 2024	Mu et al., Journal of Agriculture and Food Research, doi:10.1016/j.jafr.2024.101422	Anti-inflammatory and Nutritional Interventions Against SARS-CoV-2: A Comprehensive Review
	Review of anti-inflammatory and nutritional interventions against SARS-CoV-2. Authors emphasize the importance of a healthy immune response in reducing the severity of COVID-19, especially in high-risk groups like the elderly and those wi..
Aug 11 2024	Van Tin et al., Cells, doi:10.3390/cells13161331	Spike Protein of SARS-CoV-2 Activates Cardiac Fibrogenesis through NLRP3 Inflammasomes and NF-κB Signaling
	In vitro study showing that the SARS-CoV-2 spike protein can activate cardiac fibroblasts through ACE2-dependent mechanisms, leading to cardiac fibrosis via the NLRP3 inflammasome and NF-κB signaling pathways. The results suggest that COV..
Aug 1 2024	Hasan Anber et al., Reports of Biochemistry and Molecular Biology, doi:10.61186/rbmb.13.2.167	Assessment of Oxidative Stress Parameters in Iraqi Male Patients with COVID-19; A Case Control Study
	Case-control study of 50 COVID-19 patients and 25 healthy controls, showing significantly lower zinc, selenium, and vitamins C levels in COVID-19 patients versus healthy controls, and in ICU patients versus non-ICU patients.
Jul 24 2024	Ferreira et al., Bioscience Reports, doi:10.1042/BSR20240617	Boosting Immunity: Synergistic Antiviral Effects of Luteolin, Vitamin C, Magnesium, and Zinc Against SARS-CoV-2 3CLpro
	In vitro and in silico study showing synergistic antiviral effects of luteolin, vitamin C, magnesium, and zinc against SARS-CoV-2 3CL^pro. Authors found that luteolin inhibited SARS-CoV-2 3CL^pro with an IC₅₀ of 78 μM, which decreased 10-fo..
Jul 8 2024	Corrao et al., Journal of Clinical Medicine, doi:10.3390/jcm13133987	Safety of High-Dose Vitamin C in Non-Intensive Care Hospitalized Patients with COVID-19: An Open-Label Clinical Study
	39% lower mortality (p=0.37), 19% lower combined mortality/ICU admission (p=0.24), 102% higher ICU admission (p=0.51), and 25% shorter hospitalization (p=0.16). Prospective study of 146 hospitalized COVID-19 patients showing shorter hospitalization with high-dose intravenous vitamin C. 104 patients received 10g of vitamin C intravenously daily for 3 days and 42 patients received only standard car..
May 22 2024	Guan et al., The American Journal of the Medical Sciences, doi:10.1016/j.amjms.2024.05.005	High-dose Vitamin C Intake and COVID-19 Related Symptoms During the SARS-CoV-2 Pandemic
	31% fewer symptomatic cases (p=0.007). Retrospective 2,746 individuals in China showing significantly lower incidence of COVID-19 symptoms and fever with higher vitamin C intake, with a dose response relationship.
May 21 2024	Hemilä et al., Frontiers in Medicine, doi:10.3389/fmed.2024.1391346	Rebound effect explains the divergence in survival after 5 days in a controlled trial on vitamin C for COVID-19 patients
	Reanalysis of the REMAP-CAP and LOVIT-COVID vitamin C RCTs [Adhikari] showing that the poor results may be explained by a rebound effect due to the abrupt termination of vitamin C treatment after 4 days. Authors describe a rebound effect ..
May 10 2024	Hazan et al., Cureus, doi:10.7759/cureus.60038	Bifidobacterium Against COVID-19: A Mother and Her Newborn’s Gut Microbiome
	Case report of a mother and her newborn infected with COVID-19 within two weeks of the baby's birth. Authors propose that the disease course was altered by maternal supplementation of vitamins C and D and zinc starting after exposure on d..
Apr 16 2024	Agamah et al., ScienceOpen, doi:10.58647/DRUGARXIV.PR000010.v1	Network-based multi-omics-disease-drug associations reveal drug repurposing candidates for COVID-19 disease phases
	In silico study identifying potential drugs beneficial for COVID-19 by integrating transcriptomics, proteomics, metabolomics, lipidomics, and drug data. Authors explore interactions between drugs, molecular features, and disease severity...
Apr 4 2024	Fowler et al., NCT04344184	SAFEty Study of Early Infusion of Vitamin C for Treatment of Novel Coronavirus Acute Lung Injury (SAFE EVICT CORONA-ALI)
	19% lower mortality (p=0.75) and 2% worse results (p=0.28). RCT 47 ICU patients showing no significant differences with vitamin C treatment.
Mar 24 2024	Mosadegh et al., AMB Express, doi:10.1186/s13568-024-01690-8	NBS superfood: a promising adjunctive therapy in critically ill ICU patients with omicron variant of COVID-19
	RCT 400 critically ill ICU patients with omicron-related ARDS showing significantly reduced mortality and inflammatory markers with a nutritional supplement containing vitamins A, B1-B3, B5, B6, B9, C, D, K, and zinc, potassium, manganese..
Mar 13 2024	Arboleda et al., Behavioural Public Policy, doi:10.1017/bpp.2024.11	EAST framework to promote adherence to nutritional supplementation: a strategy to mitigate COVID-19 within health workers
	36% fewer cases (p=0.03). Prospective study of 1,063 health workers in Colombia showing lower COVID-19 infection rates with adherence to a vitamin D and C supplementation plan, however very limited baseline information is provided for the adherent vs. non-adherent..
Mar 7 2024	Kian et al., Indian Journal of Critical Care Medicine, doi:10.5005/jaypee-journals-10071-24667.4	A Retrospective Study of High-dose Intravenous Vitamin C in Critically Ill Covid-19 Patients
	Retrospective 54 critically ill COVID-19 patients showing better outcomes with 6g/day intravenous vitamin C vs. 12g/day.
Mar 4 2024	Kow et al., International Journal of Pharmacy Practice, doi:10.1093/ijpp/riae003	Impact of uricosurics on mortality outcomes in patients with COVID-19: a systematic review and meta-analysis of randomized controlled trials
	50% lower mortality (p=0.008). Systematic review and meta analysis of 27 RCTs investigating the impact of uricosuric drugs on mortality in COVID-19 patients. The pooled analysis found no significant association between uricosuric use and mortality risk. However, a subg..
Jan 30 2024	Chanyandura et al., J. Basic Appl. Pharm. Sci., doi:10.33790/jbaps1100105	Evaluation of The Pharmaceutical Quality of the Most Commonly Purchased Vitamin C (Ascorbic Acid) Formulations in COVID-19 Infection in South Africa
	Analysis of commonly purchased vitamin C supplements in South Africa during the COVID-19 pandemic finding that vitamin C tablets failed quality tests like friability and had only 18% of the labelled vitamin C content, however vitamin C ca..
Dec 20 2023	Chiscano-Camón et al., Frontiers in Medicine, doi:10.3389/fmed.2023.1301001	Vitamin C deficiency in critically ill COVID-19 patients admitted to intensive care unit
	Observational study of 43 critically ill COVID-19 patients requiring respiratory support showing vitamin C deficiency present at ICU admission and persisting throughout ICU stay. 86% of patients had undetectable vitamin C levels (<1.5mg/L..
Dec 11 2023	Hemilä et al., BMC Public Health, doi:10.1186/s12889-023-17229-8	Vitamin C reduces the severity of common colds: a meta-analysis
	Meta-analysis of 10 placebo-controlled trials showing that vitamin C treatment reduces the severity and duration of the common cold, with a greater effect on more severe outcomes.
Dec 11 2023	Morales-Bayuelo et al., F1000Research, doi:10.12688/f1000research.123550.3	New findings on ligand series used as SARS-CoV-2 virus inhibitors within the frameworks of molecular docking, molecular quantum similarity and chemical reactivity indices
	In silico analysis showing that vitamin C can stably bind within the SARS-CoV-2 RNA-dependent RNA polymerase binding pocket. Notable stabilizing interactions were seen between vitamin C and residue lysine 621, similar to the antiviral rem..
Nov 15 2023	Moatasim et al., Microorganisms, doi:10.3390/microorganisms11112777	Potent Antiviral Activity of Vitamin B12 against Severe Acute Respiratory Syndrome Coronavirus 2, Middle East Respiratory Syndrome Coronavirus, and Human Coronavirus 229E
	In vitro and in silico analysis finding that methylcobalamin, hydroxocobalamin, and cyanocobalamin forms of vitamin B12 showed broad-spectrum inhibition against SARS-CoV-2, MERS-CoV, and HCoV-229E. Methylcobalamin had the highest activity..
Nov 8 2023	Rahman et al., Molecular Mechanism Research, 1:1	Clinical & Demographical Status of Hospitalized and Non-Hospitalized Covid-19 Cases: A Multicenter Hospital Based Study in Bangladesh
	40% lower hospitalization (p=0.0001). Retrospective 416 non-hospitalized and 184 hospitalized COVID-19 patients in Bangladesh, showing higher acetaminophen and lower vitamin C usage for hospitalized patients. Confounding may be significant and baseline details per treatment g..
Nov 7 2023	Akbar et al., Nutrients, doi:10.3390/nu16071037	The Association between Lifestyle Factors and COVID-19: Findings from Qatar Biobank
	14% fewer cases (p=0.29). Retrospective 10,000 adults in Qatar, showing lower risk of COVID-19 cases with vitamin C supplementation, without statistical significance. Authors do not analyze COVID-19 severity.
Oct 25 2023	Adhikari et al., JAMA, doi:10.1001/jama.2023.21407	Intravenous Vitamin C for Patients Hospitalized With COVID-19 Two Harmonized Randomized Clinical Trials
	Very late stage (APACHE II 8 and 12 for non-critical and critical) RCT with publication delayed over a year showing higher ventilation and no significant difference in mortality with vitamin C. Authors have combined what was to be two sep..
Oct 25 2023	Adhikari et al., JAMA, doi:10.1001/jama.2023.21407	Intravenous Vitamin C for Patients Hospitalized With COVID-19 Two Harmonized Randomized Clinical Trials
	Very late stage (APACHE II 8 and 12 for non-critical and critical) RCT with publication delayed over a year showing higher ventilation and no significant difference in mortality with vitamin C. Authors have combined what was to be two sep..
Oct 6 2023	Ahmed et al., International Journal of Diabetes Management, doi:10.61797/ijdm.v2i2.259	Evaluation of the Effect of Zinc, Quercetin, Bromelain and Vitamin C on COVID-19 Patients
	Case series of 22 hospitalized COVID-19 patients showing that a combination of quercetin 800mg, bromelain 165mg, zinc acetate 50mg and vitamin C 1g daily for 3-5 days was safe when given with other treatments. Authors include in silico mo..
Sep 22 2023	Seely et al., BMJ Open, doi:10.1136/bmjopen-2023-073761	Dietary supplements to reduce symptom severity and duration in people with SARS-CoV-2: a double-blind randomised controlled trial
	14% improved recovery (p=0.41). Early terminated low-risk population (no hospitalization) very late treatment (mean 8 days) RCT with 44 patients treated with vitamin C, D, K, and zinc, and 46 control patients, showing no significant differences. Authors acknowledge that..
Sep 13 2023	Albóniga et al., Scientific Reports, doi:10.1038/s41598-023-40999-5	Differential abundance of lipids and metabolites related to SARS-CoV-2 infection and susceptibility
	Plasma metabolomic analysis showing significantly lower threonic acid levels for severe and mild COVID-19 cases compared with moderate cases. Threonic acid is a metabolite of vitamin C. The expected relationship in non-linear and depends ..
Sep 8 2023	Sun et al., Nutrition Reviews, doi:10.1093/nutrit/nuad105	Therapeutic effects of high-dose vitamin C supplementation in patients with COVID-19: a meta-analysis
	66% lower progression (p=0.03). Meta analysis of 14 studies showing lower COVID-19 progression with high-dose vitamin C treatment.
Aug 25 2023	Alkafaas et al., Virology Journal, doi:10.1186/s12985-023-02160-6	A study on the effect of natural products against the transmission of B.1.1.529 Omicron
	Review of natural products for SARS-CoV-2 omicron including an in silico study showing quercetin, curcumin, ascorbic acid, nigellidine, and chloroquine among many compounds docked to the ACE2 metallopeptidase domain. Quercetin, curcumin, ..
Aug 20 2023	Boerenkamp et al., Nutrients, doi:10.3390/nu15163653	Low Levels of Serum and Intracellular Vitamin C in Hospitalized COVID-19 Patients
	56% lower severe cases (p=0.1). Analysis of serum and intracellular vitamin C levels in hospitalized COVID-19 patients. Low vitamin C levels were common with 36% having serum levels <26 μmol/L and 15% <11 μmol/L. Intracellular vitamin C levels in peripheral blood mononu..
Jul 22 2023	Mousaviasl et al., Disease and Diagnosis, doi:10.34172/ddj.500	The Effect of a Low Dose of Vitamin C in Patients With COVID-19: A Double-Blind Randomized Controlled Trial
	20% lower mortality (p=0.64), 200% higher ventilation (p=1), and 33% higher ICU admission (p=0.79). RCT 401 hospitalized COVID-19 patients showing no significant differences with low-dose oral vitamin C (1000mg daily for 5 days).
Jul 15 2023	Graydon et al., Current Research in Immunology, doi:10.1016/j.crimmu.2023.100064	High baseline frequencies of natural killer cells are associated with asymptomatic SARS-CoV-2 infection
	Analysis of 88 COVID+ patients in the USA showing that a higher frequency of natural killer (NK) cells was associated with asymptomatic infection. Improved NK cell numbers and functioning has been shown for exercise [Oh], better sleep [Ir..
Jul 12 2023	Porter et al., medRxiv, doi:10.1101/2023.07.06.23292300	The ratio between SARS-CoV-2 RNA viral load and culturable viral titer differs depending on stage of infection
	Analysis of viral load and infectious virus, showing that the ratio between viral load (measured by PCR) and infectious virus (measured by viral culture) changes dramatically over the course of infection. Early in infection, viral load is..
Jun 28 2023	Rana et al., Biological and Clinical Sciences Research Journal, doi:10.54112/bcsrj.v2023i1.343	Effects of mega dose vitamin C in critically ill COVID-19 patients: a randomized control trial
	55% lower mortality (p=0.2), 44% lower ventilation (p=0.41), and 37% shorter hospitalization (p=0.91). RCT 278 COVID-19 ICU patients in Pakistan, showing lower mortality and ventilation, and shorter length of stay with high-dose vitamin C treatment, without statistical significance. 30 grams IV vitamin C for four days.
Jun 20 2023	Mahjoub et al., Explore, doi:10.1016/j.explore.2023.06.009	Melatonin, vitamins and minerals supplements for the treatment of Covid-19 and Covid-like illness: a prospective, randomized, double-blind multicenter study.
	67% improved recovery (p=0.32). RCT 164 low-risk (no hospitalizations) patients in Tunisia, showing improved recovery with zinc, melatonin, and vitamins A-E. This study includes COVID-19 and COVID-like illness, with 49% of 128 patients receiving a PCR test being COVID-1..
Jun 14 2023	Orellana-Manzano et al., Frontiers in Pharmacology, doi:10.3389/fphar.2023.1197973	A report on SARS-CoV-2 first wave in Ecuador: drug consumption dynamics
	Retrospective 10,175 people PCR tested in Ecuador, showing lower risk of PCR+ with multivitamin use and suggesting higher risk with acetaminophen use. The study analyzed drug consumption for COVID-19 symptoms during the 14 days before the..
Jun 1 2023	Liu et al., NCT05694975	Clinical Efficacy of Megadose Vitamin C in Severe and Critical Ill COVID-19 Patients (CEMVISCC): A Multicenter, Randomized, Single-blind, Placebo-controlled Clinical Trial
	Estimated 608 patient vitamin C late treatment RCT with results not reported over 3 years after estimated completion.
May 21 2023	Chen et al., Nutrition, doi:10.1016/j.nut.2023.112087	Early oral nutritional supplement improves COVID-19 outcomes among hospitalized older patients during the omicron wave
	PSM retrospective 1,181 COVID-19 patients ≥60 years old in China, showing significantly lower mortality with a nutritional supplement. Hospitalization time and viral clearance time was improved with earlier initiation of treatment. The su..
May 11 2023	Kyagambiddwa et al., Infection and Drug Resistance, doi:10.2147/idr.s405256	Thirty-Day Outcomes of Young and Middle-Aged Adults Admitted with Severe COVID-19 in Uganda: A Retrospective Cohort Study
	50% lower mortality (p=0.06). Retrospective 246 severe COVID-19 patients in Uganda, showing lower mortality with vitamin C treatment, without statistical significance (p = 0.06).
May 11 2023	Vaisi et al., The Clinical Respiratory Journal, doi:10.1111/crj.13632	The association between nutrients and occurrence of COVID-19 outcomes in the population of Western Iran: A cohort study
	38% lower hospitalization (p=0.17) and 10% fewer symptomatic cases (p=0.71). Analysis of nutrient intake and COVID-19 outcomes for 3,996 people in Iran, showing lower risk of COVID-19 hospitalization with sufficient vitamin A, vitamin C, and selenium intake, with statistical significance for vitamin A and selenium.
Apr 28 2023	Pincemail et al., Biomedicines, doi:10.3390/biomedicines11051308	A Pilot Study on Oxidative Stress during the Recovery Phase in Critical COVID-19 Patients in a Rehabilitation Facility: Potential Utility of the PAOT® Technology for Assessing Total Anti-Oxidative Capacity
	Analysis of 12 COVID-19 ICU patients showing vitamin C levels significantly below the reference range, and remaining low 2 months after discharge.
Apr 18 2023	Kow et al., Inflammopharmacology, doi:10.1007/s10787-023-01200-5	The effect of vitamin C on the risk of mortality in patients with COVID-19: a systematic review and meta-analysis of randomized controlled trials
	47% lower mortality (p=0.03). Meta analysis of 11 vitamin C RCTs showing significantly lower COVID-19 mortality with treatment. The effect size is larger than in our analysis due to the authors' inclusion of 2 trials that we exclude due to combined treatments being li..
Apr 9 2023	Xu et al., Nutrients, doi:10.3390/nu15081848	Association of Oral or Intravenous Vitamin C Supplementation with Mortality: A Systematic Review and Meta-Analysis
	Systematic review and meta analysis of vitamin C showing significantly lower mortality for COVID-19 and for sepsis.
Mar 21 2023	Madamombe et al., Pan African Medical Journal, doi:10.11604/pamj.2023.44.142.37858	Factors associated with COVID-19 fatality among patients admitted in Mashonaland West Province, Zimbabwe 2020-2022: a secondary data analysis
	53% lower mortality (p=0.0004). Retrospective 672 COVID-19 patients in Zimbabwe, showing lower mortality with vitamin C and azithromycin treatment, and higher mortality with dexamethasone treatment. Results are pending author clarification/correction due to internal..
Mar 21 2023	Coskun et al., SiSli Etfal Hastanesi Tip Bulteni / The Medical Bulletin of Sisli Hospital, doi:10.14744/SEMB.2022.66742	The Effect of High-dose Vitamin C Treatment for Acute Respiratory Failure due to Coronavirus Disease Pneumonia on Mortality and Length of Intensive Care Stay: A Retrospective Cohort Study
	25% lower mortality (p=0.26), 2% lower ventilation (p=1), no change in ICU admission, and 28% improved recovery (p=0.005). Retrospective 78 ICU patients in Turkey, showing lower mortality with high-dose vitamin C treatment, without statistical significance. The SOFA score was significantly better with treatment at day 4. Authors incorrectly state that "H..
Mar 21 2023	Asoudeh et al., Clinical Nutrition ESPEN, doi:10.1016/j.clnesp.2023.03.013	The association between dietary intakes of zinc, vitamin C and COVID-19 severity and related symptoms: A cross-sectional study
	69% lower severe cases (p=0.003). Retrospective 250 recovered COVID-19 patients, showing lower risk of severe cases with higher vitamin C intake.
Mar 15 2023	Schloss et al., Inflammopharmacology, doi:10.1007/s10787-023-01183-3	Nutritional deficiencies that may predispose to long COVID
	Review of 22 nutritional factors that have been linked to COVID-19 outcomes, the role of nutrients in COVID-19 infection, and the prevalence of multiple nutritional deficiencies in the population.
Mar 7 2023	Calvani et al., International Journal of Molecular Sciences, doi:10.3390/ijms24065078	Effects of l-Arginine Plus Vitamin C Supplementation on l-Arginine Metabolism in Adults with Long COVID: Secondary Analysis of a Randomized Clinical Trial
	RCT of 46 adults with long COVID showing increased serum L-arginine levels and L-arginine/ADMA ratio, a marker of nitric oxide biosynthetic capacity, with 28 days of L-arginine plus vitamin C supplementation compared to placebo. L-arginin..
Feb 28 2023	Boukef et al., NCT05670444	Melatonin, Vitamins and Minerals Supplements for the Treatment of Covid-19 and Covid-like Illness: Results of a Prospective, Randomised, Double-blinded Multicentre Study
	150 patient vitamin C early treatment RCT with results not reported over 3 years after completion.
Feb 13 2023	Yilmaz et al., Acta Biomedica Atenei Parmensis, doi:10.23750/abm.v94i1.13655	Baseline serum vitamin A and vitamin C levels and their association with disease severity in COVID-19 patients
	Analysis of 53 consecutive hospitalized COVID-19 patients and 26 matched controls, showing significantly lower vitamin A and vitamin C levels in COVID-19 patients, and a negative correlation between vitamin A and vitamin C levels and CT s..
Feb 3 2023	Yamasaki et al., Microorganisms, doi:10.3390/microorganisms11020397	Pleiotropic Functions of Nitric Oxide Produced by Ascorbate for the Prevention and Mitigation of COVID-19: A Revaluation of Pauling’s Vitamin C Therapy
	Extensive review of vitamin C and nitric oxide focusing on the potential antiviral activity of vitamin C for SARS-CoV-2 via the production of nitric oxide. Authors note that vegetables are a major dietary source of nitrate, and that dieta..
Feb 2 2023	Arora et al., Nutrients, doi:10.3390/nu15030771	Global Dietary and Herbal Supplement Use during COVID-19—A Scoping Review
	Review of 14 global studies showing that the most frequently used dietary supplements during COVID-19 were vitamin C, vitamin D, zinc, and multivitamins. The most common reason was for improved immune system functioning or reduced COVID-1..
Jan 30 2023	Sallam et al., Journal of Food and Nutrition Research, doi:10.12691/jfnr-11-1-10	Dietary Supplement Use among Children Whose Parents Work at National Research Centre: A Pilot Study
	Survey of dietary supplementation showing high usage, and greater use by more highly educated people. The survey covered 200 children whose parents were employees of a research center in Egypt, showing 50% prevalence of supplementation du..
Jan 25 2023	Turobkulovich et al., Emergent: Journal of Educational Discoveries and Lifelong Learning, doi:10.17605/OSF.IO/NSJ6B	Applications of quercetin for the prevention of COVID-19 in healthcare workers
	73% lower mortality (p=0.11) and 33% fewer symptomatic cases (p=0.03). Prospective study of healthcare workers in Uzbekistan showing lower cases with vitamin C prophylaxis. Very minimal details are provided, there is no baseline information, and control mortality is very high.
Jan 16 2023	Viglione et al., The Gazette of Medical Sciences, doi:10.46766/thegms.pubheal.22120905	Intravenous high dose vitamin C and ozonated saline effective treatment for Covid-19: The Evolution of Local Standard of Care
	Retrospective 479 high risk outpatients in the USA treated with a protocol including intravenous vitamin C, vitamin D, zinc, quercetin, bromelain, lactoferrin, HCQ, ivermectin, ozonated saline, azithromycin, ceftriaxone, methylprednisolon..
Jan 13 2023	Đukić et al., Frontiers in Bioscience-Landmark, doi:10.31083/j.fbl2801008	Inhibition of SARS-CoV-2 Mpro with Vitamin C, L-Arginine and a Vitamin C/L-Arginine Combination
	In vitro study showing inhibition of SARS-CoV-2 M^pro with vitamin C, L-arginine, and improved inhibition with the combination of both.
Dec 14 2022	Labbani-Motlagh et al., Journal of Research in Pharmacy Practice, doi:10.4103/jrpp.jrpp_30_22	High-dose intravenous Vitamin C in early stages of severe acute respiratory syndrome coronavirus 2 infection: A double-blind, randomized, controlled clinical trial
	33% lower mortality (p=0.74), 13% longer hospitalization (p=0.49), and 16% lower progression (p=0.12). RCT 74 patients in Iran, showing no significant differences in outcomes with high-dose vitamin C treatment. Tables 1b and 2a show conflicting baseline SOFA scores. The percentages of patients receiving antiviral treatments and corticoster..
Dec 6 2022	Lamontagne et al., NCT04401150	Lessening Organ Dysfunction With VITamin C - COVID
	392 patient vitamin C late treatment RCT with results not reported over 3 years after completion. The companion non-COVID trial NCT03680274 has reported results.
Nov 26 2022	Sharif et al., Nutrients, doi:10.3390/nu14235029	Impact of Zinc, Vitamins C and D on Disease Prognosis among Patients with COVID-19 in Bangladesh: A Cross-Sectional Study
	46% lower severe cases (p=0.001). Retrospective 962 COVID-19 patients in Bangladesh, showing significantly lower severity with vitamin C, vitamin D, and zinc supplementation, and improved results from the combination of all three. Table 2 has a typographical error where t..
Nov 23 2022	Tosato et al., Nutrients, doi:10.3390/nu14234984	Effects of l-Arginine Plus Vitamin C Supplementation on Physical Performance, Endothelial Function, and Persistent Fatigue in Adults with Long COVID: A Single-Blind Randomized Controlled Trial
	46 patient RCT in Italy showing improved recovery from long COVID symptoms using combined treatment with L-arginine and vitamin C. See also [Calvani]
Nov 16 2022	Guldemir et al., Work, doi:10.3233/wor-220292	Clinical characteristics of bus drivers and field officers infected with COVID-19: A cross-sectional study from Istanbul
	31% lower hospitalization (p=0.05). Retrospective 477 COVID+ public transportation workers in Turkey, showing lower risk of hospitalization with vitamin C use in unadjusted results.
Oct 19 2022	Doocy et al., PLOS Global Public Health, doi:10.1371/journal.pgph.0000924	Clinical progression and outcomes of patients hospitalized with COVID-19 in humanitarian settings: A prospective cohort study in South Sudan and Eastern Democratic Republic of the Congo
	63% lower mortality (p=0.22). Prospective study of 144 hospitalized COVID-19 patients in the DRC and South Sudan, showing lower mortality with vitamin C treatment.
Oct 18 2022	Cosentino et al., Journal of Clinical Medicine, doi:10.3390/jcm11206138	Early Outpatient Treatment of COVID-19: A Retrospective Analysis of 392 Cases in Italy
	Retrospective 392 outpatients in Italy showing 0.2% mortality with early treatment, compared with >3% in Italy at the time. Treatment varied for individual patients and included HCQ, vitamin D, vitamin C, vitamin A, zinc, quercetin, bromh..
Oct 10 2022	Olczak-Pruc et al., Nutrients, doi:10.3390/nu14194217	Vitamin C Supplementation for the Treatment of COVID-19: A Systematic Review and Meta-Analysis
	56% lower mortality (p=0.004). Systematic review and meta analysis of 19 studies showing lower mortality with vitamin C treatment, statistically significant for RCTs but not for non-RCT studies, and longer ICU length of stay.
Sep 22 2022	Özgülteki̇n et al., Kastamonu Medical Journal, doi:10.51271/KMJ-0059	The effect of high-dose vitamin C on renal functions in COVID–19 patients
	5% higher mortality (p=1). Retrospective 43 ICU patients in Turkey, 21 treated with vitamin C, showing no significant difference in mortality and increased renal failure. Treatment included stage 1 AKI patients. Vitamin C 45-50 g/day for 5 days.
Sep 19 2022	Mosadegh et al., Microbial Pathogenesis, doi:10.1016/j.micpath.2022.105792	The effect of Nutrition Bio-shield superfood (NBS) on disease severity and laboratory biomarkers in patients with COVID-19: A randomized clinical trial
	61% lower mortality (p=0.002) and 28% shorter hospitalization (p=0.001). RCT 70 hospitalized severe COVID-19 patients in Iran, showing lower mortality and improved clinical markers with treatment combining vitamins A, B1-B3, B5, B6, B9, C, D, K, and magnesium, potassium, phosphorus, sulfur, manganese, calcium,..
Sep 2 2022	Foshati et al., Food Science & Nutrition, doi:10.1002/fsn3.3034	Antioxidants and clinical outcomes of patients with coronavirus disease 2019: A systematic review of observational and interventional studies
	Systematic review showing that vitamin C, vitamin D, selenium, and zinc can improve COVID-19 clinical outcomes.
Aug 30 2022	Kumar et al., Journal of Family Medicine and Primary Care, doi:10.4103/jfmpc.jfmpc_2437_21	Efficacy of intravenous vitamin C in management of moderate and severe COVID-19: A double blind randomized placebo controlled trial
	23% lower mortality (p=0.6) and 21% lower ventilation (p=0.6). RCT 60 ICU patients in India, showing no significant difference in outcomes with vitamin C. Mortality was lower in the vitamin C arm despite having more severe cases at baseline (87% vs. 67%). 1 gram intravenous vitamin C 8 hourly for fou..
Aug 18 2022	Gkioulekas et al., COVID, doi:10.3390/covid2080084	Statistical Analysis Methods Applied to Early Outpatient COVID-19 Treatment Case Series Data
	Retrospective analysis of case series data from 3,164 high-risk COVID-19 outpatients treated with early multidrug protocols similar to the McCullough protocol, including hydroxychloroquine, ivermectin, zinc, azithromycin, vitamin C, vitam..
Aug 16 2022	Loucera et al., Virology Journal, doi:10.1186/s12985-023-02195-9 (date from preprint)	Real-world evidence with a retrospective cohort of 15,968 COVID-19 hospitalized patients suggests 21 new effective treatments
	28% lower mortality (p=0.002). Retrospective 15,968 COVID-19 hospitalized patients in Spain, showing lower mortality with existing use of several medications including metformin, HCQ, azithromycin, aspirin, vitamin D, vitamin C, and budesonide. Since only hospitalized ..
Aug 15 2022	Sinnberg et al., Antioxidants, doi:10.3390/antiox11081580	Vitamin C Deficiency in Blood Samples of COVID-19 Patients
	42% lower mortality (p=0.38), 41% lower ventilation (p=0.17), and 61% lower hospitalization (p=0.05). Analysis of 74 COVID-19 patients and 8 controls in Germany, showing low vitamin C levels associated with mortality. There was no significant difference for vitamin A, D, or E levels. Very few group details are provided, for example the ag..
Aug 8 2022	Bhowmik et al., Health Science Reports, doi:10.1002/hsr2.762	Impact of high-dose vitamin C on the mortality, severity, and duration of hospital stay in COVID-19 patients: A meta-analysis
	46% lower mortality (p<0.0001). Meta analysis of 15 studies with 2,125 COVID-19 patients showing significantly lower mortality with high-dose vitamin C.
Jul 27 2022	Fogleman et al., The Journal of the American Board of Family Medicine, doi:10.3122/jabfm.2022.04.210529	A Pilot of a Randomized Control Trial of Melatonin and Vitamin C for Mild-to-Moderate COVID-19
	4% improved recovery (p=0.83). Early terminated low-risk patient RCT with 32 low-dose vitamin C, 32 melatonin, and 34 placebo patients, showing faster resolution of symptoms with melatonin in spline regression analysis, and no significant difference for vitamin C. All ..
Jul 19 2022	Izzo et al., Pharmacological Research, doi:10.1016/j.phrs.2022.106360	Combining L-Arginine with Vitamin C Improves Long-COVID Symptoms: The Nationwide Multicenter LINCOLN Study
	41% improved recovery (p<0.0001). Long COVID trial comparing L-arginine + vitamin C with multivitamin treatment (vitamin B1, B2, B6, B12, nicotinamide, folic acid, pantothenic acid), showing significant improvement in symptoms with L-arginine + vitamin C treatment.
Jul 15 2022	Zuo et al., EMBO reports, doi:10.15252/embr.202256374 (date from preprint)	Vitamin C promotes ACE2 degradation and protects against SARS‐CoV‐2 infection
	In vitro and mouse study showing that vitamin C inhibits SARS-CoV-2. Vitamin C lowered ACE2 protein levels in a dose-dependent manner at a concentration of 1-10mM in both cell and humanized ACE2 mouse models.
Jun 16 2022	Ortore et al., International Journal of Translational Medicine, doi:10.3390/ijtm2020022	Evaluation of the Clinical Effects of an Antiviral, Immunostimulant and Antioxidant Phytotherapy in Patients Suffering from COVID-19 Infection: An Observational Pilot Study
	Retrospective case series of 240 patients in Italy in 2020, up to 96 years old, showing no mortality and 1.6% hospitalization with early treatment including vitamin C, quercetin, and green tea and red wine polyphenols. The formulation was..
Jun 7 2022	Usanma Koban et al., Bratislava Medical Journal, doi:10.4149/BLL_2022_082	The factors affecting the prolonged PCR positivity in COVID-19 patients
	33% improved viral clearance (p=0.73). Retrospective 126 patients in Turkey, showing no significant difference in PCR+ at day 14 with vitamin C treatment.
May 30 2022	Kumar et al., Cureus, doi:10.7759/cureus.25467	Efficacy and Safety of Aspirin, Promethazine, and Micronutrients for Rapid Clinical Recovery in Mild to Moderate COVID-19 Patients: A Randomized Controlled Clinical Trial
	57% improved recovery (p=0.25). RCT 260 patients in India, 130 treated with aspirin, promethazine, vitamin C, D, B3, zinc, and selenium, showing faster recovery with treatment. There was no hospitalization, ICU admission, or supplemental oxygen requirements in either gr..
May 27 2022	Galmés et al., Nutrients, doi:10.3390/nu14112254	Suboptimal Consumption of Relevant Immune System Micronutrients Is Associated with a Worse Impact of COVID-19 in Spanish Populations
	Ecological study in Spain, showing lower intake of vitamin D, A, B9, and zinc in regions with the highest COVID-19 incidence and mortality. Vitamin D intake was associated with lower prevalence, incidence, and a combined incidence+mortali..
May 19 2022	Hellou et al., Journal of Cellular and Molecular Medicine, doi:10.1111/jcmm.17337	Effect of ArtemiC in patients with COVID-19: A Phase II prospective study
	77% improved recovery (p=0.04), 92% lower need for oxygen therapy (p=0.01), 13% shorter hospitalization (p=0.92), and 10% improved viral clearance (p=0.77). RCT 50 hospitalized patients in Israel, 33 treated with curcumin, vitamin C, artemisinin, and frankincense oral spray, showing improved recovery with treatment.
May 18 2022	Yildirim et al., Research Square, doi:10.21203/rs.3.rs-1666161/v1	Mortality Predictors Of Pre-variant SARS-CoV-2 Infected ARDS Patients Receiving Favipiravir and Tocilizumab
	Retrospective 60 ICU patients in Turkey treated with tocilizumab and favipiravir, reporting that there was a higher rate of vitamin C treatment in surviving patients (35% vs 10%; p = 0.03), however the results in the table do not match. T..
May 15 2022	Galindo et al., NCT05029037	High-dose Intravenous Vitamin C (HDIVC) as Adjuvant Therapy in Critical Patients With Positive COVID-19. A Pilot Randomized Controlled Dose-comparison Trial.
	Estimated 160 patient vitamin C late treatment RCT with results not reported over 4 years after estimated completion.
May 13 2022	Zangeneh et al., Obesity Medicine, doi:10.1016/j.obmed.2022.100420	Survival analysis based on body mass index in patients with COVID-19 admitted to the intensive care unit of Amir Al-Momenin Hospital in Arak – 2021
	4% lower mortality (p=0.86). Retrospective 193 ICU patients in Iran, showing no significant difference with vitamin C treatment. This study has multiple data issues: The text states that 134 people died and 59 were discharged. However, in Table 1, the column labeled ..
Apr 20 2022	Pandya et al., Informatics in Medicine Unlocked, doi:10.1016/j.imu.2022.100951	Unravelling Vitamin B12 as a potential inhibitor against SARS-CoV-2: A computational approach
	In silico study showing significant interaction with SARS-CoV-2 targets for multiple vitamins.
Mar 29 2022	Hess et al., Internal and Emergency Medicine, doi:10.1007/s11739-022-02954-6	High-dose intravenous vitamin C decreases rates of mechanical ventilation and cardiac arrest in severe COVID-19
	20% lower mortality (p=0.54), 40% lower ventilation (p=0.05), and 27% lower ICU admission (p=0.11). Retrospective 100 severe condition hospitalized patients in the USA, 25 treated with high-dose IV vitamin C, showing lower mechanical ventilation and cardiac arrest, and increased length of survival with treatment. 3g IV vitamin C every ..
Mar 19 2022	Coppock et al., Life, doi:10.3390/life12030453	Pharmacologic Ascorbic Acid as Early Therapy for Hospitalized Patients with COVID-19: A Randomized Clinical Trial
	50% greater improvement (p=0.16) and 22% higher hospital discharge (p=0.07). RCT with 66 very late stage (8 days from symptom onset) hospitalized patients, 44 treated with vitamin C and 22 control patients, showing no significant differences with treatment.
Mar 11 2022	Salehi et al., Research Square, doi:10.21203/rs.3.rs-1362678/v1	Risk factors of death in mechanically ventilated COVID-19 patients: a retrospective multi-center study
	10% lower mortality (p=0.56). Retrospective 125 mechanically ventilated ICU patients in Iran, showing no significant difference with vitamin C treatment in unadjusted results.
Feb 28 2022	Shehab et al., Tropical Journal of Pharmaceutical Research, doi:10.4314/tjpr.v21i2.13	Immune-boosting effect of natural remedies and supplements on progress of, and recovery from COVID-19 infection
	4% lower severe cases (p=1). Retrospective survey-based analysis of 349 COVID-19 patients, showing no significant difference with vitamin C prophylaxis in unadjusted analysis. REC/UG/2020/03.
Feb 28 2022	Nimer et al., Bosnian Journal of Basic Medical Sciences, doi:10.17305/bjbms.2021.7009	The impact of vitamin and mineral supplements usage prior to COVID-19 infection on disease severity and hospitalization
	25% lower hospitalization (p=0.08) and 17% lower severe cases (p=0.18). Retrospective 2,148 COVID-19 recovered patients in Jordan, showing lower risk of severity and hospitalization with vitamin C prophylaxis, without statistical significance.
Feb 26 2022	Hajdrik et al., Foods, doi:10.3390/foods11050694	In Vitro Determination of Inhibitory Effects of Humic Substances Complexing Zn and Se on SARS-CoV-2 Virus Replication
	In vitro study of a humic substance containing vitamin C, selemium ions, and zinc ions, showing 50% SARS-CoV-2 inhibition at picomolar concentrations.
Feb 24 2022	Kory et al., Journal of Clinical Medicine Research, doi:10.14740/jocmr4658	“MATH+” Multi-Modal Hospital Treatment Protocol for COVID-19 Infection: Clinical and Scientific Rationale
	Review of the data supporting the MATH+ hospital treatment protocol for COVID-19.
Feb 20 2022	Quek et al., Clinical and Translational Medicine, doi:10.1002/ctm2.731	Zinc and vitamin C intake increases spike and neutralising antibody production following SARS‐CoV‐2 infection
	Antibody response analysis of 422 SARS-CoV-2 infected men in an RCT showing zinc + vitamin C treatment increased anti-SARS-CoV-2 spike IgG and neutralizing antibody levels compared to other treatments (vitamin C, hydroxychloroquine, iverm..
Feb 11 2022	Gavrielatou et al., Frontiers in Medicine, doi:10.3389/fmed.2022.814587	Effect of Vitamin C on Clinical Outcomes of Critically Ill Patients With COVID-19: An Observational Study and Subsequent Meta-Analysis
	58% lower mortality (p=0.11). Retrospective 113 consecutive mechanically ventilated COVID+ ICU patients in Greece, 10 receiving high-dose IV vitamin C, showing lower mortality with treatment, without statistical significance (p=0.11). The associated meta analysis incl..
Jan 29 2022	Mohajeri et al., Mediterranean Journal of Nutrition and Metabolism, doi:10.3233/MNM-211521	The difference in the dietary inflammatory index, functional food, and antioxidants intake between COVID-19 patients and healthy persons
	Retrospective dietary survey analysis of 500 COVID-19 patients and 500 healthy matched controls in Iran, showing that COVID-19 patients had lower daily consumption of vitamin C, vitamin D, vitamin E, zinc, and selenium. IR.ARUMS.REC.1400...
Jan 21 2022	Goc et al., European Journal of Microbiology and Immunology, doi:10.1556/1886.2021.00022	Inhibitory effects of specific combination of natural compounds against SARS-CoV-2 and its Alpha, Beta, Gamma, Delta, Kappa, and Mu variants
	In vitro study testing combinations of plant extracts and micronutrients with several variants of SARS-CoV-2. A combination of vitamin C, N-acetylcysteine, curcumin, quercetin, resveratrol, theaflavin, naringenin, baicalin, and broccoli e..
Jan 15 2022	Yang et al., American Journal of Translational Research, 14:1	Traditional Chinese medicine together with high-dose vitamin C improves the therapeutic effect of western medicine against COVID-19
	33% faster recovery (p<0.0001) and 36% faster viral clearance (p<0.0001). Prospective study of 60 patients in China with three arms: SOC, SOC+TCM, and SOC+TCM+high-dose vitamin C, showing successively faster recovery with the addition of TCM and the addition of high-dose vitamin C. TCM included inhaled vitamin ..
Jan 13 2022	Tu et al., Infectious Diseases & Immunity, doi:10.1097/ID9.0000000000000037	Risk Factors for Severity and Mortality in Adult Patients Confirmed with COVID-19 in Sierra Leone: A Retrospective Study
	83% lower mortality (p<0.0001). Retrospective 180 hospitalized COVID-19 patients in Sierra Leone, showing lower mortality with vitamin C treatment in unadjusted results.
Jan 3 2022	Hemilä et al., Life, doi:10.3390/life12010062	Bias against Vitamin C in Mainstream Medicine: Examples from Trials of Vitamin C for Infections
	Analysis of bias against vitamin C for infections in major studies and editorials.
Dec 28 2021	Baguma et al., Research Square, doi:10.21203/rs.3.rs-1193578/v1	Characteristics of the COVID-19 patients treated at Gulu Regional Referral Hospital, Northern Uganda: A cross-sectional study
	48% higher mortality (p=0.54). Retrospective COVID+ hospitalized patients in Uganda, 385 patients receiving vitamin C treatment, showing higher mortality with treatment, without statistical significance.
Dec 15 2021	Majidi et al., Frontiers in Immunology, doi:10.3389/fimmu.2021.717816	The Effect of Vitamin C on Pathological Parameters and Survival Duration of Critically Ill Coronavirus Disease 2019 Patients: A Randomized Clinical Trial
	14% lower mortality (p=0.03). RCT 100 ICU patients in Iran, 31 treated with vitamin C, showing lower mortality with treatment.
Dec 14 2021	Amssayef et al., Cardiovascular & Hematological Disorders-Drug Targets, doi:10.2174/1871529X21666211214153308	Vitamin C inhibits Angiotensin-Converting Enzyme-2 in Isolated Rat Aortic Ring
	Ex vivo study showing vitamin C inhibiting vascular ACE2.
Nov 30 2021	Deschasaux-Tanguy et al., BMC Medicine, doi:10.1186/s12916-021-02168-1	Nutritional risk factors for SARS-CoV-2 infection: a prospective study within the NutriNet-Santé cohort
	Analysis of 7,766 adults in France, showing higher intakes of vitamin C, folate, vitamin K, dietary fibre, and fruit and vegetables associated with lower seropositivity.
Nov 30 2021	Xia et al., Nutrition, doi:10.1016/j.nut.2021.111405	High-dose intravenous vitamin C attenuates hyperinflammation in severe coronavirus disease 2019
	Retrospective study of 236 hospitalized patients with severe COVID-19 in China. 85 patients received high-dose intravenous vitamin C (HIVC) along with standard care, 151 received standard care alone. Most patients showed signs of hyperinf..
Nov 25 2021	Ried et al., Cureus, doi:10.7759/cureus.19902	Therapies to Prevent Progression of COVID-19, Including Hydroxychloroquine, Azithromycin, Zinc, and Vitamin D3 With or Without Intravenous Vitamin C: An International, Multicenter, Randomized Trial
	31% improved recovery (p=0.008). RCT 237 patients in Turkey, 162 treated with IV vitamin C in addition to HCQ/AZ/zinc/vitamin D used for all patients, showing significantly faster recovery with the addition of IV vitamin C. 97% of patients were vitamin D deficient, and l..
Nov 14 2021	Beigmohammadi et al., Trials, doi:10.1186/s13063-021-05795-4	The effect of supplementation with vitamins A, B, C, D, and E on disease severity and inflammatory responses in patients with COVID-19: a randomized clinical trial
	89% lower mortality (p=0.11), 41% lower hospitalization (p=0.25), and 45% improved recovery (p=0.001). Small RCT 60 ICU patients in Iran, 30 treated with vitamins A, B, C, D, and E, showing significant improvement in SOFA score and several inflammatory markers at day 7 with treatment. 5,000 IU vitamin A daily, 600,000 IU vitamin D once, 30..
Nov 8 2021	Tehrani et al., Urology Journal, doi:10.22037/uj.v18i.6863	An investigation into the Effects of Intravenous Vitamin C on Pulmonary CT Findings and Clinical Outcomes of Patients with COVID 19 Pneumonia A Randomized Clinical Trial
	87% lower mortality (p=0.13) and 18% shorter hospitalization (p=0.23). RCT 54 late stage patients, 18 treated with IV vitamin C (2g every 6h for 5 days), showing significant relative improvements in oxygen saturation and respiratory rate.
Oct 28 2021	Shousha et al., World Journal of Gastroenterology, doi:10.3748/wjg.v27.i40.6951	Hepatic and gastrointestinal disturbances in Egyptian patients infected with coronavirus disease 2019: A multicentre cohort study
	94% lower mortality (p=0.003). Retrospective 547 hospitalized COVID+ patients in Egypt, showing lower mortality with vitamin C treatment. Treatment was applied according to the official guidelines, indicating that vitamin C was co-administered with HCQ. Actual treatmen..
Oct 25 2021	Leal-Martínez et al., International Journal of Environmental Research and Public Health, doi:10.3390/ijerph19031172 (date from preprint)	Effect of a Nutritional Support System to Increase Survival and Reduce Mortality in Patients with COVID-19 in Stage III and Comorbidities: A Blinded Randomized Controlled Clinical Trial
	86% lower mortality (p=0.03) and 57% lower ventilation (p=0.31). 80 patient RCT with 40 patients treated with a comprehensive regimen of nutritional support, showing significantly lower mortality with treatment. Treatment contained cholecalciferol, vitamin C, zinc, spirulina maxima, folic acid, glutami..
Sep 27 2021	Simsek et al., Annals of Medical Research, doi:10.5455/annalsmedres.2020.10.1043	Effects of high dose vitamin C administration in Covid-19 patients
	44% lower mortality (p=0.19) and 10% lower ICU admission (p=0.66). Retrospective 139 hospitalized patients in Turkey, 58 treated with high-dose vitamin C, showing improved kidney functioning with treatment. Mortality was lower with treatment, but not reaching statistical significance with the small sampl..
Sep 22 2021	Zheng et al., Open Medicine, doi:10.1515/med-2021-0361	No significant benefit of moderate-dose vitamin C on severe COVID-19 cases
	157% higher mortality (p=0.33) and 35% worse improvement (p=0.17). Retrospective 397 severe COVID-19 patients in China, showing worse outcomes with vitamin C treatment, without statistical significance. IV vitamin C 2-4g/day. Subject to confounding by indication and immortal time bias. Exclusion criteria..
Sep 7 2021	Xia et al., Aging, doi:10.18632/aging.203503	High-dose vitamin C ameliorates cardiac injury in COVID-19 pandemic: a retrospective cohort study
	Retrospective study of 113 severe and critically ill COVID-19 patients with cardiac injury in China. 70 patients had ameliorated cardiac injury (ACI) and 43 had non-ameliorated cardiac injury (NACI) at day 21. 51 patients received high-do..
Sep 1 2021	Sharmin et al., NCT04558424	Randomized, Double -Blind, Placebo Controlled, Trial to Evaluate the Effect of Zinc and Ascorbic Acid Supplementation in COVID-19 Positive Hospitalized Patients in BSMMU
	Estimated 50 patient vitamin C late treatment RCT with results not reported over 5 years after estimated completion.
Aug 17 2021	Capone et al., Cureus, doi:10.7759/cureus.9809	Characterization of Critically Ill COVID-19 Patients at a Brooklyn Safety-Net Hospital
	Retrospective 102 ICU patients in the USA, 73 receiving vitamin C and zinc, showing a negative correlation of treatment with mortality, but not reaching statistical significance (p = 0.31).
Aug 4 2021	Mohseni et al., Nutrition & Food Science, doi:10.1108/NFS-11-2020-0421	Do body mass index (BMI) and history of nutritional supplementation play a role in the severity of COVID-19? A retrospective study
	44% more cases (p=0.002). Retrospective 603 patients in Iran, 34 taking vitamin C supplements, showing increased risk of COVID-19 cases in unadjusted results. IR.SHOUSHTAR.REC.1399.015.
Jul 26 2021	Tan et al., QJM: An International Journal of Medicine, doi:10.1093/qjmed/hcab184	Efficacy of diammonium glycyrrhizinate combined with vitamin C for treating hospitalized COVID-19 patients: a retrospective, observational study
	25% lower combined mortality/intubation (p=0.74) and 73% lower progression (p=0.002). PSM retrospective 207 hospitalized patients in China, 46 treated with diammonium glycyrrhizinate and vitamin C, showing lower risk of ARDS with treatment.
Jul 9 2021	Rabail et al., Food Science & Nutrition, doi:10.1002/fsn3.2458	Nutritional and lifestyle changes required for minimizing the recovery period in home quarantined COVID-19 patients of Punjab, Pakistan
	Survey of 80 recovered COVID-19 patients in Pakistan, showing faster recovery with vitamin C, vitamin D, and zinc supplementation.
Jul 7 2021	Hazan et al., medRxiv, doi:10.1101/2021.07.06.21259924	Effectiveness of ivermectin-based multidrug therapy in severely hypoxic, ambulatory COVID-19 patients
	100% lower mortality (p=0.04) and 100% lower hospitalization (p=0.001). Small study of 24 consecutive patients in serious condition (9 days post symptoms, mean SpO₂ 87.4) using combined treatment with ivermectin, doxycycline, zinc, vitamin D, and vitamin C, showing no mortality or hospitalization with treatme..
Jul 6 2021	Margolin et al., Journal of Evidence-Based Integrative Medicine, doi:10.1177/2515690X211026193	20-Week Study of Clinical Outcomes of Over-the-Counter COVID-19 Prophylaxis and Treatment
	94% fewer cases (p=0.003). Retrospective 113 outpatients, 53 (patient choice) treated with zinc, quercetin, vitamin C/D/E, l-lysine, and quina, showing lower cases with treatment. Results are subject to selection bias and limited information on the groups is provid..
Jul 4 2021	Özgünay et al., The European Research Journal, doi:10.18621/eurj.938778	The use of vitamin C in the intensive care unit during the COVID-19 pandemic
	9% lower mortality (p=0.69) and 1% higher ventilation (p=1). Retrospective 160 ICU patients, 32 with raised neutrophil/lymphocyte ratio treated with vitamin C, showing no significant differences.
Jun 30 2021	Vishnuram et al., Indian Journal of Basic and Applied Medical Research, doi:10.36848/IJBAMR/2020/29215.55599	Role of high dose oral liposomal vitamin C in reducing mortality in patients with COVID-19
	54% lower mortality (p=0.03). Retrospective 8,634 hospitalized patients in India, showing lower mortality with high-dose vitamin C in unadjusted results. No group details are provided, the text and table appear to show different results, and some numbers do not match.
Jun 8 2021	Li et al., Journal of Pharmacy Practice, doi:10.1177/08971900211015052	Use of Intravenous Vitamin C in Critically Ill Patients With COVID-19 Infection
	11% higher mortality (p=1). PSM retrospective 8 ICU patients treated with vitamin C and 24 matched controls, showing no significant difference. Authors note that "it is possible for the delayed timing of IV vitamin C to have blunted the beneficial effects as th..
Jun 1 2021	May et al., British Journal of Pharmacology, doi:10.1111/bph.15579	Therapeutic potential of megadose vitamin C to reverse organ dysfunction in sepsis and COVID-19
	Review of data supporting the use of megadose vitamin C as a treatment for sepsis and COVID-19.
May 26 2021	Pourhoseingholi et al., Research Square, doi:10.21203/rs.3.rs-365321/v2	Case Characteristics, Clinical Data, And Outcomes of Hospitalized COVID-19 Patients In Qom Province, Iran: A Prospective Cohort Study
	13% lower mortality (p=0.38). Prospective study of 2,468 hospitalized COVID-19 patients in Iran, showing no significant difference with vitamin C treatment. IR.MUQ.REC.1399.013.
May 11 2021	Aldwihi et al., International Journal of Environmental Research and Public Health, doi:10.3390/ijerph18105086	Patients’ Behavior Regarding Dietary or Herbal Supplements before and during COVID-19 in Saudi Arabia
	36% lower hospitalization (p=0.006). Retrospective survey-based analysis of 738 COVID-19 patients in Saudi Arabia, showing lower hospitalization with vitamin C, turmeric, zinc, and nigella sativa, and higher hospitalization with vitamin D. For vitamin D, most patients contin..
May 11 2021	Suna et al., Med. Clin. (Barc.), doi:10.1016/j.medcli.2021.04.010	Effect of high-dose intravenous vitamin C on prognosis in patients with SARS-CoV-2 pneumonia
	21% lower mortality (p=0.52) and 2% higher ICU admission (p=1). Retrospective 323 hospitalized patients, 153 treated with vitamin C, showing no significant differences. Patients in each group were in different time periods, with the vitamin C group first. Time based confounding is possible due to impr..
May 3 2021	Malla et al., bioRxiv, doi:10.1101/2021.05.02.442358	Vitamin C inhibits SARS coronavirus-2 main protease essential for viral replication
	In Silico and in vitro study showing that vitamin C inhibits SARS-CoV-2 3CL^pro. Authors note that the different clinical results may be explained in part by the widely varying dosages used, and they conclude that vitamin C and/or derivati..
Apr 30 2021	Elhadi et al., PLOS ONE, doi:10.1371/journal.pone.0251085	Epidemiology, outcomes, and utilization of intensive care unit resources for critically ill COVID-19 patients in Libya: A prospective multi-center cohort study
	12% higher mortality (p=0.15). Prospective study of 465 COVID-19 ICU patients in Libya showing no significant differences with treatment.
Apr 22 2021	Zhao et al., Frontiers in Pharmacology, doi:10.3389/fphar.2021.638556	High Dose Intravenous Vitamin C for Preventing The Disease Aggravation of Moderate COVID-19 Pneumonia. A Retrospective Propensity Matched Before-After Study
	72% lower progression (p=0.03) and 8% slower viral clearance (p=0.79). PSM retrospective 110 patients, 55 treated with high-dose IV vitamin C, showing lower progression to severe disease with treatment. Patients in each group were in different time periods, time based confounding is likely due to SOC improvi..
Apr 14 2021	Hakamifard et al., Immunopathologia Persa, doi:10.34172/ipp.2022.08	The effect of vitamin E and vitamin C in patients with COVID-19 pneumonia; a randomized controlled clinical trial
	46% lower ICU admission (p=0.46) and 1% shorter hospitalization (p=0.82). RCT with 38 patients treated with vitamin C and vitamin E, and 34 control patients, showing lower ICU admission with treatment, but not statistically significant.
Apr 8 2021	Abdulateef et al., Open Medicine, doi:10.1515/med-2021-0273	COVID-19 severity in relation to sociodemographics and vitamin D use
	19% lower hospitalization (p=0.69). Survey of 428 recovered COVID-19 patients in Iraq, showing fewer hospital visits for patients on prophylactic vitamin C or D. Hospitalization was lower for those on vitamin C, D, or zinc, without statistical significance. The study observ..
Apr 8 2021	Gadhiya et al., BMJ Open, doi:10.1136/bmjopen-2020-042549	Clinical characteristics of hospitalised patients with COVID-19 and the impact on mortality: a single-network, retrospective cohort study from Pennsylvania state
	1% higher mortality (p=0.99). Retrospective 283 patients in the USA showing higher mortality with all treatments (not statistically significant). Confounding by indication is likely. In the supplementary appendix, authors note that the treatments were usually given fo..
Apr 7 2021	Mulhem et al., BMJ Open, doi:10.1136/bmjopen-2020-042042	3219 hospitalised patients with COVID-19 in Southeast Michigan: a retrospective case cohort study
	32% higher mortality (p=0.01). Retrospective database analysis of 3,219 hospitalized patients in the USA. Very different results in the time period analysis (Table S2), and results significantly different to other studies for the same medications (e.g., heparin OR 3.06..
Apr 2 2021	Al Sulaiman et al., Research Square, doi:10.21203/rs.3.rs-354711/v1	Ascorbic Acid as an Adjunctive Therapy in Critically Ill Patients with COVID-19: A Multicenter Propensity Score Matched Study
	15% lower mortality (p=0.27). Retrospective 158 critically ill patients receiving vitamin C and propensity matched controls, showing mortality OR 0.77 [0.48-1.23], and statistically significantly lower thrombosis, OR 0.42 [0.18-0.94]. 1000mg of vitamin C was given dai..
Mar 30 2021	Holt et al., Thorax, doi:10.1136/thoraxjnl-2021-217487	Risk factors for developing COVID-19: a population-based longitudinal study (COVIDENCE UK)
	3% more cases (p=0.86). Prospective survey-based study with 15,227 people in the UK, showing lower risk of COVID-19 cases with vitamin A, vitamin D, zinc, selenium, probiotics, and inhaled corticosteroids; and higher risk with metformin and vitamin C. Statistica..
Mar 8 2021	Hamidi-Alamdari et al., Clinical and Translational Investigation, doi:10.24875/RIC.21000028	Methylene blue for treatment of hospitalized COVID-19 patients: a randomized, controlled, open-label clinical trial, phase 2
	44% lower mortality (p=0.38) and 38% shorter hospitalization (p=0.004). RCT 80 hospitalized patients with severe COVID-19, 40 treated with methylene blue + vitamin C + N-acetylcysteine, showing lower mortality, shorter hospitalization, and significantly improved SpO₂ and respiratory distress with treatment.
Mar 2 2021	Hemilä et al., Research Square, doi:10.21203/rs.3.rs-289381/v1	Vitamin C may increase the recovery rate of outpatient cases of SARS-CoV-2 infection by 70%: reanalysis of the COVID A to Z Randomized Clinical Trial
	Reanalysis of Thomas et al. showing that vitamin C increased the recovery rate by 70%, p = 0.025.
Feb 28 2021	Bejan et al., Clinical Pharmacology & Therapeutics, doi:10.1002/cpt.2376 (date from preprint)	DrugWAS: Drug‐wide Association Studies for COVID‐19 Drug Repurposing
	34% lower mortality (p=0.33), 25% lower ventilation (p=0.47), 15% lower ICU admission (p=0.65), and no change in hospitalization (p=1). Retrospective 9,748 COVID-19 patients in the USA showing lower risk of mortality, ventilation, and ICU admission with vitamin C prophylaxis, without statistical significance.
Feb 26 2021	Gao et al., Aging, doi:10.18632/aging.202557	The efficiency and safety of high-dose vitamin C in patients with COVID-19: a retrospective cohort study
	86% lower mortality (p=0.04). Retrospective 76 COVID-19 patients, 46 treated with intravenous high-dose vitamin C, showing lower mortality and improved oxygen requirements with treatment. Dosage was 6g intravenous infusion per 12hr on the first day, and 6g once for th..
Feb 15 2021	Mahto et al., American Journal of Blood Research, 11:1	Seroprevalence of IgG against SARS-CoV-2 and its determinants among healthcare workers of a COVID-19 dedicated hospital of India
	26% higher IgG positivity (p=0.49). Retrospective 689 healthcare workers in India, showing no significant difference in IgG positivity with vitamin C prophylaxis.
Feb 12 2021	Thomas et al., JAMA Network Open, doi:10.1001/jamanetworkopen.2021.0369	Effect of High-Dose Zinc and Ascorbic Acid Supplementation vs Usual Care on Symptom Length and Reduction Among Ambulatory Patients With SARS-CoV-2 Infection: The COVID A to Z Randomized Clinical Trial
	18% faster recovery (p=0.15). Small 214 low-risk outpatient RCT showing non-statistically significant faster recovery with zinc and with vitamin C. A secondary analysis concludes that vitamin C increases recovery rate by 71% (p = 0.036) [pubpeer.com]. See also..
Feb 9 2021	Hancock et al., SSRN, doi:10.2139/ssrn.3779211	Case Cluster of RT-PCR COVID-19 Positive Patients with an Unexpected Benign Clinical Course With Vitamin D, Melatonin, Vitamin C, and Viscum Album
	Case series of 24 COVID-19 patients (12 confirmed PCR+) treated with vitamin D, vitamin C, and melatonin, showing positive outcomes with no patient having worse than a mild case, including 7 high risk patients.
Feb 1 2021	Muhammad et al., SAGE Open Medicine, doi:10.1177/2050312121991246	Deficiency of antioxidants and increased oxidative stress in COVID-19 patients: A cross-sectional comparative study in Jigawa, Northwestern Nigeria
	Case control study with 50 symptomatic COVID-19 patients and 21 healthy controls in Nigeria, showing that COVID-19 patients had significantly lower levels of selenium and zinc, and vitamins A, C, and E. Control patients were younger than ..
Feb 1 2021	Zhao et al., Ann. Palliat. Med., doi:10.21037/apm-20-1387	Beneficial aspects of high dose intravenous vitamin C on patients with COVID-19 pneumonia in severe condition: a retrospective case series study
	Retrospective case study of 12 severe/critical COVID-19 patients finding that high dose IV vitamin C improved inflammatory response, immune and organ function. There was no control group.
Jan 31 2021	He et al., NCT04664010	Efficacy and Safety of High-dose Vitamin C Combined With Traditional Chinese Medicine in the Treatment of Moderate and Severe Coronavirus Pneumonia (COVID-19)
	60 patient vitamin C late treatment RCT with results not reported over 5 years after completion.
Jan 27 2021	Xing et al., Journal of Pharmaceutical and Biomedical Analysis, doi:10.1016/j.jpba.2021.113927	Vitamin C supplementation is necessary for patients with coronavirus disease: An ultra-high-performance liquid chromatography-tandem mass spectrometry finding
	Prospective study with 31 COVID-19 patients and 60 controls reporting on a new method to assess plasma vitamin C concentrations. Vitamin C was deficient (11.4µmol/l vs. 52µmol/l for healthy controls), and returned to a normal range (76µmo..
Jan 19 2021	Abioye et al., BMJ Global Health, doi:10.1136/bmjgh-2020-003176	Effect of micronutrient supplements on influenza and other respiratory tract infections among adults: a systematic review and meta-analysis
	Systematic review and meta-analysis of 80 randomized controlled trials showing reduced risk of acute respiratory infections with vitamin C and vitamin D, and shorter duration of symptoms with vitamin C, vitamin D, and zinc.
Jan 18 2021	Hemilä et al., Frontiers in Medicine, doi:10.3389/fmed.2020.559811	Vitamin C and COVID-19
	Review of the use of vitamin C for infections and the potential benefit for COVID-19.
Jan 9 2021	JamaliMoghadamSiahkali et al., Research Square, doi:10.21203/rs.3.rs-139942/v1	Safety and Effectiveness of High-Dose Vitamin C in Patients with COVID-19; A Randomized Controlled open-label Clinical Trial
	25% higher ventilation (p=1) and 31% longer hospitalization (p=0.03). Small late stage RCT for the addition of vitamin C to HCQ and lopinavir/ritonavir, with 30 treatment and 30 control patients, finding a significant reduction in temperature and a significant improvement in oxygenation after 3 days in the ..
Dec 23 2020	Su et al., BioScience Trends, doi:10.5582/bst.2020.03340	Efficacy of early hydroxychloroquine treatment in preventing COVID-19 pneumonia aggravation, the experience from Shanghai, China
	135% higher progression (p=0.18) and 34% slower improvement (p=0.04). Retrospective 616 patients in China showing increased risk of disease progression with vitamin C treatment.
Dec 16 2020	Jang et al., Heart & Lung, doi:10.1016/j.hrtlng.2020.10.010	Clinical course of COVID-19 patients treated with ECMO: A multicenter study in Daegu, South Korea
	51% improved recovery (p=0.15). Retrospective 19 COVID-19 ECMO patients in South Korea, showing a higher rate of weaning from ECMO with vitamin C treatment, without statistical significance. Authors perform multivariate analysis but do not provide full results, only rep..
Dec 15 2020	Darban et al., Journal of Cellular & Molecular Anesthesia, doi:10.22037/jcma.v6i2.32182	Efficacy of High Dose Vitamin C, Melatonin and Zinc in Iranian Patients with Acute Respiratory Syndrome due to Coronavirus Infection: A Pilot Randomized Trial
	33% lower progression (p=1) and 6% shorter ICU admission (p=0.3). Small RCT in Iran with 20 ICU patients, 10 treated with high-dose vitamin C, melatonin, and zinc, showing no significant differences. This study has several data issues: The study reports a mean age of 59 ± 19 years with a range of 20-65 ..
Dec 10 2020	Rosenthal et al., JAMA Network Open, doi:10.1001/jamanetworkopen.2020.29058	Risk Factors Associated With In-Hospital Mortality in a US National Sample of Patients With COVID-19
	11% lower mortality (p=0.005). Retrospective database analysis of 64,781 hospitalized patients in the USA, showing lower mortality with vitamin C or vitamin D (authors do not distinguish between the two), and higher mortality with zinc and HCQ, statistically significan..
Dec 7 2020	Holford et al., Nutrients, doi:10.3390/nu12123760	Vitamin C—An Adjunctive Therapy for Respiratory Infection, Sepsis and COVID-19
	Review of vitamin C use for respiratory infections including COVID-19 and the mechanisms of action. Authors note that evidence to date indicates oral vitamin C (2-8 g/day) may reduce the incidence and duration of respiratory infections, a..
Nov 30 2020	Kumari et al., Cureus, doi:10.7759/cureus.11779	The Role of Vitamin C as Adjuvant Therapy in COVID-19
	36% lower mortality (p=0.45), 20% lower ventilation (p=0.67), 26% faster recovery (p=0.0001), and 24% shorter hospitalization (p=0.0001). RCT 150 hospitalized patients in Pakistan showing 26% faster recovery, p < 0.0001. 36% lower mortality, not statistically significant due to the small number of events. Dosage was 50 mg/kg/day of intravenous vitamin C.
Nov 30 2020	Louca et al., BMJ Nutrition, Prevention & Health, doi:10.1136/bmjnph-2021-000250 (date from preprint)	Modest effects of dietary supplements during the COVID-19 pandemic: insights from 445 850 users of the COVID-19 Symptom Study app
	no change in cases (p=1). Survey analysis of dietary supplements showing no significant difference in PCR+ cases with vitamin C usage in the UK, however significant reductions were found in the US and Sweden. These results are for PCR+ cases only, they do not refl..
Nov 16 2020	Arslan et al., SSRN, doi:10.2139/ssrn.3682517	Synergistic Effect of Quercetin and Vitamin C Against COVID-19: Is a Possible Guard for Front Liners
	92% fewer cases (p=0.03). Small prophylaxis RCT with 113 patients showing fewer cases with quercetin + vitamin C + bromelain prophylaxis. Note that this paper disappeared from SSRN without explanation. This paper has multiple data issues: Impossible follow-up dura..
Nov 3 2020	Behera et al., PLOS ONE, doi:10.1371/journal.pone.0247163 (date from preprint)	Role of ivermectin in the prevention of SARS-CoV-2 infection among healthcare workers in India: A matched case-control study
	18% fewer cases (p=0.58). Retrospective matched case-control prophylaxis study for HCQ, ivermectin, and vitamin C with 372 healthcare workers, showing lower COVID-19 incidence for all treatments, with statistical significance reached for ivermectin. HCQ OR 0.56, p..
Oct 1 2020	Patel et al., Chest Infections, doi:10.1016/j.chest.2020.08.322	The significance of oral ascorbic acid in patients with COVID-19
	29% lower mortality (p=0.18). Retrospective 176 hospitalized patients, 96 treated with oral vitamin C (from 500mg to 1500mg daily), showing lower mortality with treatment.
Sep 20 2020	Yüksel et al., Intensive Care Medicine Experimental, 9:S1, 001458, doi:10.1186/s40635-021-00413-8	Effects of high dose vitamin c on patient outcomes in ARDS patients admitted to intensive care with COVID-19; multi-center retrospective study
	19% lower mortality (p=0.04). PSM retrospective 86 ICU patients on mechanical ventilation in Turkey, showing lower mortality with high-dose vitamin C treatment (≥200mg/kg for 4 days).
Sep 8 2020	Arvinte et al., Med. Drug Discov, doi:10.1016/j.medidd.2020.100064	Serum Levels of Vitamin C and Vitamin D in a Cohort of Critically Ill COVID-19 Patients of a North American Community Hospital Intensive Care Unit in May 2020: A Pilot Study
	Pilot study with 21 ICU patients finding low serum levels of vitamin C and vitamin D in most patients. Older age and low vitamin C level appeared to be co-dependent risk factors for mortality.
Sep 8 2020	Galmés et al., Nutrients, doi:10.3390/nu12092738	Current State of Evidence: Influence of Nutritional and Nutrigenetic Factors on Immunity in the COVID-19 Pandemic Framework
	Ecological study of European countries analyzing 10 vitamins and minerals endorsed by the European Food Safety Authority as having sufficient evidence for a causal relationship between intake and optimal immune system function: vitamins D..
Aug 26 2020	Chiscano-Camón et al., Critical Care, doi:10.1186/s13054-020-03249-y	Vitamin C levels in patients with SARS-CoV-2-associated acute respiratory distress syndrome
	Small study of 18 COVID-19 ARDS patients showing that vitamin C levels were very low - 17 patients had undetectable levels and one had a low level (2.4 mg/L).
Aug 10 2020	Zhang et al., Annals of Intensive Care, doi:10.1186/s13613-020-00792-3	Pilot Trial of High-dose vitamin C in critically ill COVID-19 patients (preprint 8/10/2020)
	50% lower mortality (p=0.2). Small RCT for high-dose vitamin C for ICU patients showing reduced (but not statistically significant) mortality. Dosage was 12g of vitamin C/50ml every 12 hours for 7 days at a rate of 12ml/hour.
Aug 1 2020	Hiedra et al., Expert Review of Anti-infective Therapy, doi:10.1080/14787210.2020.1794819	The use of IV vitamin C for patients with COVID-19: a case series
	Case study of 17 patients receiving IV vitamin C for COVID-19, finding a significant decrease in inflammatory markers, including ferritin and D-dimer, and a trend to decreasing FiO₂ requirements, after vitamin C administration. There was ..
Jul 25 2020	Feyaerts et al., Nutrition, doi:10.1016/j.nut.2020.110948	Vitamin C as prophylaxis and adjunctive medical treatment for COVID-19?
	Review concluding that there is clear evidence that vitamin C in high doses can reduce interleukin-6 and endothelin-1 mediators. Authors suggest a relatively low dose as prophylaxis, and in cases of severe COVID-19, an (intravenous) high-..
Jul 20 2020	Krishnan et al., Journal of Clinical Anesthesia, doi:10.1016/j.jclinane.2020.110005	Clinical comorbidities, characteristics, and outcomes of mechanically ventilated patients in the State of Michigan with SARS-CoV-2 pneumonia
	31% lower mortality (p=0.04). Retrospective 152 mechanically ventilated patients in the USA showing unadjusted lower mortality with vitamin C, vitamin D, HCQ, and zinc treatment, statistically significant only for vitamin C.
Jun 19 2020	Biancatelli et al., Frontiers in Immunology, doi:10.3389/fimmu.2020.01451	Quercetin and Vitamin C: An Experimental, Synergistic Therapy for the Prevention and Treatment of SARS-CoV-2 Related Disease (COVID-19)
	Review of the evidence for the use of vitamin C and quercetin both for prophylaxis in high-risk populations and for the treatment of COVID-19 patients.
May 27 2020	Kumar et al., VirusDisease, doi:10.1007/s13337-020-00643-6 (date from preprint)	In silico virtual screening-based study of nutraceuticals predicts the therapeutic potentials of folic acid and its derivatives against COVID-19
	In silico analysis finding that magnesium ascorbate, a form of Vitamin C, was found to be the top compound among 106 nutraceuticals for binding to M^pro of SARS-CoV-2.
Mar 11 2013	Thomas et al., JAMA Internal Medicine, doi:10.1001/jamainternmed.2013.2296	Ascorbic Acid Supplements and Kidney Stone Incidence Among Men: A Prospective Study
	Prospective study of 23,355 Swedish men showing a 2-fold increased risk of kidney stone formation with high-dose ascorbic acid supplement use. Authors note that ascorbic acid is excreted in urine both unmetabolized and as oxalate, which i..
Oct 1 2009	EFSA, EFSA Journal, doi:10.2903/j.efsa.2009.1226	Scientific Opinion on the substantiation of health claims related to vitamin C and protection of DNA, proteins and lipids from oxidative damage (ID 129, 138, 143, 148), antioxidant function of lutein (ID 146), maintenance of vision (ID 141, 142), collagen formation (ID 130, 131, 136, 137, 149), function of the nervous system (ID 133), function of the immune system (ID 134), function of the immune system during and after extreme physical exercise (ID 144), non-haem iron absorption (ID 132, 147), energy-yielding metabolism (ID 135), and relief in case of irritation in the upper respiratory tract (ID 1714, 1715) pursuant to Article 13(1) of Regulation (EC) No 1924/2006
	European Food Safety Administration review concluding that there is a causal relationship between the intake of vitamin C and immune system function.
Jul 31 1993	Vojdani et al., Nutrition Research, doi:10.1016/S0271-5317(05)80799-7	In vivo effect of ascorbic acid on enhancement of human natural killer cell activity
	Analysis of 20 healthy subjects in the USA showing that vitamin C increases natural killer (NK) cell activity. [Graydon] showed that a lower frequency of natural killer cells was associated with symptomatic COVID-19 infection.