Conv. Plasma
Nigella Sativa

All vitamin C studies
Meta analysis
study COVID-19 treatment researchVitamin CVitamin C (more..)
Melatonin Meta
Metformin Meta
Azvudine Meta
Bromhexine Meta Molnupiravir Meta
Budesonide Meta
Colchicine Meta
Conv. Plasma Meta Nigella Sativa Meta
Curcumin Meta Nitazoxanide Meta
Famotidine Meta Paxlovid Meta
Favipiravir Meta Quercetin Meta
Fluvoxamine Meta Remdesivir Meta
Hydroxychlor.. Meta Thermotherapy Meta
Ivermectin Meta

All Studies   Meta Analysis    Recent:   

Vitamin C reduces the severity of common colds: a meta-analysis

Hemilä et al., BMC Public Health, doi:10.1186/s12889-023-17229-8
Dec 2023  
  Source   PDF   All Studies   Meta AnalysisMeta
Vitamin C for COVID-19
7th treatment shown to reduce risk in September 2020
*, now known with p = 0.000000098 from 67 studies, recognized in 10 countries.
No treatment is 100% effective. Protocols combine complementary and synergistic treatments. * >10% efficacy in meta analysis with ≥3 clinical studies.
3,800+ studies for 60+ treatments.
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.
Hemilä et al., 11 Dec 2023, peer-reviewed, 2 authors. Contact:
This PaperVitamin CAll
Vitamin C reduces the severity of common colds: a meta-analysis
Harri Hemilä, Elizabeth Chalker
BMC Public Health, doi:10.1186/s12889-023-17229-8
Background Randomized trials have shown that vitamin C shortens the duration of common colds. Some trials reported greater effects on severe cold symptoms compared with mild symptoms. This review systematically compares the effects of vitamin C on severe and mild common cold symptoms. Methods We included all placebo-controlled trials of orally administered vitamin C in doses of at least 1 g/day for the common cold for people in good health at baseline. The analysis was restricted to trials which reported both the total duration of the common cold, and the severity of the common cold measured using severity scales, the duration of more severe stages of the cold, or proxies for severe colds such as days indoors. Findings were pooled using the inverse variance, fixed effect options of the metacont function of the R package meta to calculate the ratio of means estimate. Results Fifteen comparisons from 10 trials which reported both mild and severe symptoms were identified. All trials were randomized and double-blind. Compared to placebo, vitamin C significantly decreased the severity of the common cold by 15% (95% CI 9-21%). The direct comparison of the effect of vitamin C on mild and severe symptoms was limited to five comparisons which found that vitamin C had a significant benefit on the duration of severe symptoms. In this subset, there was a significant difference in the size of the effect of vitamin C on the overall duration of colds versus the duration of severe colds (P = 0.002), and vitamin C had no significant effect on the duration of mild symptoms. Conclusions The common cold is the leading cause of acute morbidity and a major cause of absenteeism from work and school. However, absenteeism is dependent on the severity of symptoms. The finding that vitamin C may have a greater effect on more severe measures of the common cold is therefore important. Further research on the therapeutic effects of vitamin C on the common cold should measure outcomes of differing levels of severity.
Supplementary Information The online version contains supplementary material available at https://doi. org/10.1186/s12889-023-17229-8. Supplementary Material 1: Search for the trials, Figs. S1-S5, Description of the included trials. Supplementary Material 2: Spreadsheet describing the calculations. Authors' contributions HH planned the study, collected the data, carried out the statistical analysis and wrote the draft manuscript. EC confirmed the collected data and participated in the revision of the manuscript. Both authors read and approved the final manuscript. Funding No external funding. Open Access funding provided by University of Helsinki (including Helsinki University Central Hospital). Data availability All data generated or analysed during this study are included in this published article and its supplementary information files. Declarations Ethics approval and consent to participate Not applicable. This is a systematic review of studies already published. Consent for publication Not applicable. Competing interests The authors declare no competing interests. Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Anderson, Beaton, Corey, Spero, Winter illness and vitamin C: the effect of relatively low doses, Can Med Assoc J
Anderson, Reid, Beaton, Vitamin C and the common cold [Correction], Can Med Assoc J
Anderson, Reid, Beaton, Vitamin C and the common cold: a double-blind trial, Can Med Assoc J
Anderson, Suranyi, Beaton, The effect on winter illness of large doses of vitamin C, Can Med Assoc J
Ang, Pullar, Currie, Vissers, Vitamin C and immune cell function in inflammation and cancer, Biochem Soc Trans, doi:10.1042/BST20180169
Balduzzi, Rücker, Schwarzer, How to perform a meta-analysis with R: a practical tutorial, Evid Based Ment Health, doi:10.1136/ebmental-2019-300117
Barnett, Linder, Antibiotic prescribing for adults with acute bronchitis in the United States, 1996-2010, JAMA, doi:10.1001/jama.2013.286141
Bessel-Lorck, Common cold prophylaxis in young people at a ski-camp, Medizinische, doi:10.5281/zenodo.6514016
Carr, Einstein, Lai, Martin, Starmer, Vitamin C and the common cold: a second MZ cotwin control study, Acta Genet Med Gemellol, doi:10.1017/s0001566000006450
Carr, Maggini, Vitamin C and immune function, Nutrients, doi:10.3390/nu9111211
Cerullo, Negro, Parimbelli, Pecoraro, Perna et al., The long history of vitamin C: from prevention of the common cold to potential aid in the treatment of COVID-19, Front Immunol, doi:10.3389/fimmu.2020.574029
Constantini, Dubnov-Raz, Eyal, Berry, Cohen et al., The effect of vitamin C on upper respiratory infections in adolescent swimmers: a randomized trial, Eur J Pediatr, doi:10.1007/s00431-010-1270-z
Core, R Project for Statistical Computing
Davies, Hughes, Jones, Reed, Craig et al., Metabolism of ascorbic acid (vitamin C) in subjects infected with common cold viruses, Biochem Med, doi:10.1016/0006-2944(79)90058-9
Eccles, Is the common cold a clinical entity or a cultural concept?, Rhinology, doi:10.4193/rhino12.123
Elwood, Lee, Leger, Baird, Howard, A randomized controlled trial of vitamin C in the prevention and amelioration of the common cold, Br J Prev Soc Med, doi:10.1136/jech.30.3.193
Fendrick, Monto, Nightengale, Sarnes, The economic burden of non-influenza-related viral respiratory tract infection in the United States, Arch Intern Med, doi:10.1001/archinte.163.4.487
Friedrich, Adhikari, Beyene, Ratio of means for analyzing continuous outcomes in meta-analysis performed as well as mean difference methods, J Clin Epidemiol, doi:10.1016/j.jclinepi.2010.09.016
Goodwin, Tangum, Battling quackery: attitudes about micronutrient supplements in American academic medicine, Arch Intern Med, doi:10.1001/archinte.158.20.2187
Havers, Hicks, Chung, Gaglani, Murthy et al., Outpatient antibiotic prescribing for acute respiratory infections during influenza seasons, JAMA Netw Open, doi:10.1001/jamanetworkopen.2018.0243
Hemilä, Carr, Chalker, 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, Front Immunol, doi:10.3389/fimmu.2021.674681
Hemilä, Carr, Li, Guo, Li et al., Comment on 'Therapeutic target and molecular mechanism of vitamin C-treated pneumonia: a systematic study of network pharmacology, Food Funct, doi:10.1039/d0fo02189j
Hemilä, Chalker, Assessment of vitamin C effects on pneumonia and COVID-19 using Mendelian randomization: analysis may be misleading, Eur J Clin Nutr, doi:10.1038/s41430-022-01091-9
Hemilä, Chalker, Bias against vitamin C in mainstream medicine: examples from trials of vitamin C for infections, Life, doi:10.3390/life12010062
Hemilä, Chalker, Commentary: the long history of vitamin C: from prevention of the common cold to potential aid in the treatment of COVID-19, Front Immunol, doi:10.3389/fimmu.2021.659001
Hemilä, Chalker, Commentary: vitamin C supplementation for prevention and treatment of pneumonia, Front Med, doi:10.3389/fmed.2020.595988
Hemilä, Chalker, De Man, Vitamin C may improve left ventricular ejection fraction: a meta-analysis, Front Cardiovasc Med, doi:10.3389/fcvm.2022.789729
Hemilä, Chalker, Meta-analysis on vitamin C and the common cold in children may be misleading, Eur J Clin Pharmacol, doi:10.1007/s00228-019-02733-x
Hemilä, Chalker, Vitamin C and the common cold in children: severe flaws in the meta-analyses by Vorilhon
Hemilä, Chalker, Vitamin C for preventing and treating the common cold, Cochrane Database Syst Rev, doi:10.1002/14651858.cd000980.pub4
Hemilä, Chalker, Vitamin C may reduce the duration of mechanical ventilation in critically ill patients: a meta-regression analysis, J Intensive Care, doi:10.1186/s40560-020-0432-y
Hemilä, De Man, Vitamin C and COVID-19, Front Med, doi:10.3389/fmed.2020.559811
Hemilä, Do vitamins C and E affect respiratory infections?
Hemilä, Duration of the common cold and similar continuous outcomes should be analyzed on the relative scale: a case study of two zinc lozenge trials, BMC Med Res Methodol, doi:10.1186/s12874-017-0356-y
Hemilä, Erroneous data in a meta-analysis on vitamin C and the common cold, PubPeer
Hemilä, Herman, Vitamin C and the common cold: a retrospective analysis of Chalmers' review, J Am Coll Nutr, doi:10.1080/07315724.1995.10718483
Hemilä, Louhiala, Vitamin C for preventing and treating pneumonia, Cochrane Database Syst Rev, doi:10.1002/14651858.cd005532.pub3
Hemilä, Louhiala, Vitamin C may affect lung infections, J R Soc Med, doi:10.1177/014107680710001109
Hemilä, Shortcomings in the vitamin C and common cold meta-analysis by Ran
Hemilä, Statistical problems in the vitamin C and common cold trial with South Korean army recruits [Rapid response, BMJ Mil Health
Hemilä, Vitamin C and common cold-induced asthma: a systematic review and statistical analysis, Allergy Asthma Clin Immunol, doi:10.1186/1710-1492-9-46
Hemilä, Vitamin C and infections, Nutrients, doi:10.3390/nu9040339
Hemilä, Vitamin C and sex differences in respiratory tract infections, Respir Med, doi:10.1016/j.rmed.2007.12.011
Hemilä, Vitamin C intake and susceptibility to the common cold, Discussion, doi:10.1017/s0007114500002889
Hemilä, Vitamin C may alleviate exercise-induced bronchoconstriction: a meta-analysis, BMJ Open, doi:10.1136/bmjopen-2012-002416
Hemilä, Vitamin C supplementation and common cold symptoms: factors affecting the magnitude of the benefit, Med Hypotheses, doi:10.1054/mehy.1997.0639
Hemilä, Vitamin C supplementation and common cold symptoms: problems with inaccurate reviews, Nutrition, doi:10.1016/s0899-9007(96)00223-7
Hemilä, Vitamin C supplementation and the common cold: was Linus Pauling right or wrong?, Int J Vitam Nutr Res
Hemilä, Vitamin, the placebo effect, and the common cold: a case study of how preconceptions influence the analysis of results [Discussion in 1996:49:1085-1087, J Clin Epidemiol, doi:10.1016/0895-4356(96)00189-8
Himmelstein, Robergs, Koehler, Lewis, Qualls, Vitamin C supplementation and upper respiratory tract infections in marathon runners, J Exerc Physiol Online
Hoaglin, Misunderstandings about Q and Cochran's Q test in meta-analysis, Stat Med, doi:10.1002/sim.6632
Hui, Nelson, Lin, Zhao, The role of vitamin C in pneumonia and COVID-19 infection in adults with European ancestry: a Mendelian randomisation study, Eur J Clin Nutr, doi:10.1038/s41430-021-00993-4
Hume, Weyers, Changes in leucocyte ascorbic acid during the common cold, Scott Med J, doi:10.1177/003693307301800102
Johnston, Alonso-Coello, Friedrich, Mustafa, Tikkinen et al., Do clinicians understand the size of treatment effects? A randomized survey across 8 countries, CMAJ, doi:10.1503/cmaj.150430
Johnston, Barkyoumb, Schumacher, Vitamin C supplementation slightly improves physical activity levels and reduces cold incidence in men with marginal vitamin C status: a randomized controlled trial, Nutrients, doi:10.3390/nu6072572
Karlowski, Chalmers, Frenkel, Kapikian, Lewis et al., Ascorbic acid for the common cold: a prophylactic and therapeutic trial, JAMA, doi:10.1001/jama.1975.03240220018013
Kim, Lim, Byun, Vitamin C supplementation reduces the odds of developing a common cold in Republic of Korea Army recruits: randomised controlled trial, BMJ Mil Health, doi:10.1136/bmjmilitary-2019-001384
Li, Guo, Li, Liang, Yang et al., Therapeutic target and molecular mechanism of vitamin C-treated pneumonia: a systematic study of network pharmacology, Food Funct, doi:10.1039/d0fo00421a
Louhiala, Hemilä, Can CAM treatments be evidence-based? Focus Altern, Complement Ther, doi:10.1111/fct.12110
Ludvigsson, Hansson, Tibbling, Vitamin C as a preventive medicine against common colds in children, Scand J Infect Dis, doi:10.3109/inf.1977.9.issue-2.07
Manning, Mitchell, Appadurai, Shakya, Pierce et al., Vitamin C promotes maturation of T-cells, Antioxid Redox Signal, doi:10.1089/ars.2012.4988
Markwell, Vitamin C in the prevention of colds, Med J Australia, doi:10.5694/j.1326-5377.1947.tb74386.x
Miegl, Use of vitamin C in otorhinolaryngology [in German; translation available, Wien Med Wochenschr, doi:10.5281/zenodo.6514695
Miller, Nance, Norton, Wolen, Griffith et al., Therapeutic effect of vitamin C: a co-twin control study, JAMA, doi:10.1001/jama.1977.03270300052006
Padhani, Moazzam, Ashraf, Bilal, Salam et al., Vitamin C supplementation for prevention and treatment of pneumonia, Cochrane Database Syst Rev, doi:10.1002/14651858.cd013134.pub2
Pauling, The significance of the evidence about ascorbic acid and the common cold, Proc Natl Acad Sci, doi:10.1073/pnas.68.11.2678
Pitt, Costrini, Vitamin C prophylaxis in marine recruits, JAMA, doi:10.1001/jama.1979.03290350028016
Ran, Zhao, Wang, Wang, Zhao et al., Extra dose of vitamin C based on a daily supplementation shortens the common cold: a meta-analysis of 9 randomized controlled trials, Biomed Res Int, doi:10.1155/2018/1837634
Retracted, Extra dose of vitamin C based on a daily supplementation shortens the common cold: a meta-analysis of 9 randomized controlled trials, Biomed Res Int, doi:10.1155/2023/9848057
Ritzel, Ascorbic acid and the common cold [letter, JAMA, doi:10.1001/jama.1976.03260370018017
Ritzel, Critical analysis of the role of vitamin C in the prophylaxis and treatment of the common cold [in German; translation available, Helv Med Acta, doi:10.5281/zenodo.6546378
Ruskin, Calcium cevitamate (calcium ascorbate) in the treatment of acute rhinitis, Ann Otol Rhinol Laryngol, doi:10.1177/000348943804700218
Sabiston, Radomski, Health problems and vitamin C in Canadian Northern Military operations, doi:10.5281/zenodo.7303680
Saeed, Abdelrahim, A meta-analysis of the effectiveness of vitamin C in the prevention and treatment of childhood upper respiratory tract infections, J Clin Nurs Res, doi:10.26689/jcnr.v7i1.4403
Schwartz, Togo, Hornick, Tominaga, Gleckman, Evaluation of the efficacy of ascorbic acid in prophylaxis of induced rhinovirus 44 infection in man, J Infect Dis, doi:10.1093/infdis/128.4.500
Schwarzer, Carpenter, Rucker, Meta-analysis with R, doi:10.1007/978-3-319-21416-0
Shamseer, Vohra, Bax, Spee, Madderom et al., Commentaries on 'Vitamin C for preventing and treating the common cold' with responses from the review author, Evid Based Child Health: A Cochrane Rev J, doi:10.1002/ebch.261
Thomas, Patel, Bittel, Wolski, Wang et al., Effect of highdose 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, JAMA Netw Open, doi:10.1001/jamanetworkopen.2021.0369
Vitamin, Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium and Carotenoids, doi:10.17226/9810
Vorilhon, Arpajou, Roussel, Merlin, Pereira et al., Retraction note: efficacy of vitamin C for the prevention and treatment of upper respiratory tract infection: a meta-analysis in children, Eur J Clin Pharmacol, doi:10.1007/s00228-021-03150-9
Vorilhon, Arpajou, Roussel, Pereira, Cabaillot, Efficacy of vitamin C for the prevention and treatment of upper respiratory tract infection: a meta-analysis in children, Eur J Clin Pharmacol, doi:10.1007/s00228-018-2601-7
Please send us corrections, updates, or comments. c19early involves the extraction of 100,000+ datapoints from thousands of papers. Community updates help ensure high accuracy. Vaccines and treatments are complementary. All practical, effective, and safe means should be used based on risk/benefit analysis. No treatment, vaccine, or intervention is 100% available and effective for all current and future variants. We do not provide medical advice. Before taking any medication, consult a qualified physician who can provide personalized advice and details of risks and benefits based on your medical history and situation. FLCCC and WCH provide treatment protocols.
  or use drag and drop