Table 1.
Summary of systematic reviews of vitamin C in the management of acute respiratory infection and disease.
| Author | Year | Type of Review | Review duration | Types of Studies included | Databases Used | Intervention Searched | Participants included (condition of interest) | Publication years of including studies | Number of Studies included | The number of Types of Studies included | Administration of Vitamin C | Total number of participants in the Review | Dose | Control or Placebo | N in intervetion and placebo | Measure of Outcome | Outcome |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Identification | Methods | Methods and Dose | Outcomes | ||||||||||||||
| Hemila | 2013 | Meta-analysis | Inception to September 2013 | Intervention studies (randomised/non-randomised; placebo-controlled/non-placebo-controlled) | Medline (OVID), Scopus, Cochrane Central Register of Controlled Trials | oral or intravenous vitamin C (ascorbic acid or its salts) as a single or multiple doses | children and adults of either sex at any age (common cold-induced asthma) | 1980−1990 | 3 | 2 x randomised-double blind placebo-controlled trial (1 x cross-over) and 1 x self-controlled study | Not specified | N=79 | 1 g/day; 5 g/day; 2 g/single dose | Placebo x 2; no control x 1 | Vit C (22 + 23 + 9 = 54); placebo (19 + 23 = 42) | Frequency of asthma attacks; | Incidence of all asthma attacks RR = 0.22; Incidence of severe and moderate asthma attacks RR = 0.11 |
| sensitivity to histamine; | 52 % decrease in proportion of participants sensitive to histamine | ||||||||||||||||
| asthma symptom score; | No significant difference | ||||||||||||||||
| PEF; | No significant difference | ||||||||||||||||
| PC20 | 3.2 fold increase | ||||||||||||||||
| Hemila | 2004 | Systematic review | 1999−2002 | Intervention studies (placebo-controlled/non-placebo-controlled) | Medline, SCISEARCH, EMBASE | unrestricted | military personnel; students in crowded lodgings; marathon runners (respiratory infections) | 1942−1996 | 12 | 8 x randomised, double-blind, placebo controlled trial; 2x non-placebo-controlled trial; 2 x poorly described methodology | Oral; dietary fortication | N=1394 | 0.05−2 g/day for 7days - 6 months | Placebo x 8; Non-placebo x 2; Unclear x 2 | (vit c = 561; control = 833) | Severity of colds | 1.87 vs 1.97 [p = .012] |
| duration of colds (days); | No significant difference | ||||||||||||||||
| Incidence and duration of specific symptoms; | Constitutional symptoms: 0.8 v 2.4 days [p = .045], 8v21 case [p = .006]. Other symptom categories not significant | ||||||||||||||||
| hospital stays (days) | 10.1 v 16.7 [p = .012] | ||||||||||||||||
| hospital admissions | 18v83 [p = .09] | ||||||||||||||||
| Hemila and Chalker | 2013 | Systematic review | 2010−2012 | Intervention studies (placebo-controlled only) | CENTRAL, MEDLINE, Embase, CINAHL, LILACS, Web of Science | Minimum of 0.2 g/day vitamin C | Children and adults of either gender and any age (common cold) | 1950−2001 | 20 (43 additional studies reported prevention rather than treatment outcomes) | 17 x placebo-controlled trials in community; 3 placebo-controlled laboratory trials | Oral | N = 3249 | 1−8 g/day for 1−4 days | Placebo | Vit C = 1968; Control = 1281 | Duration of colds | No statistical significance |
| Mean days off work/school (severity) | Diff: -0.08 [p = .048] | ||||||||||||||||
| Hemila and Louhiala | 2017 | Systematic review | 1950−2011 | Intervention studies (placebo-controlled/non-placebo-controlled) | Cochrane Central Register of Controlled Trials 2011, Medline, EMBASE, Web of Science | Vitamin C only (ascorbic acid or its salts) to one trial group, orally or IV as a single dose (allowed in treatment studies) or multiple doses, with no other nutrient substances | No age restriction | 1970−1994 | 5 (3 x prophylactic and 2 x treatment trials) | 2 x 'quasi-placebo control'; 2 x randomised double-blind placebo-controlled; 1 x no placebo, blinding not described | 1 x oral dietary fortification; 4 x not specified | N = 2532 | 0.05 to 0.3 g/day for 6 months; 0.2 g/day for up to 4 weeks; 0.3 g/day for unspecified duration; 2 mg per 2000 antibiotic units (0.5–1.6 g/day) or 1 mg per 2000 antibiotic units (0.25 to 0.8 g/day) for unspecified duration | 2 x no placebo; 1 x low-dose vit. C used as placebo in primary comparison; 2 x placebo | Vit C = 878; control 1282; placebo 372 | Community-acquired: Severity of pneumonic episodes | Reduced severity score (-2.31) at four weeks (p = .053) for patients with higher respiratory scores on admission |
| Community-acquired: Duration of pneumonic episodes | −4.0 days in high vitamin C compared with low vitamin C arm (p < .0001) | ||||||||||||||||
| Community-acquired: Death caused by pneumonia | No evidence available | ||||||||||||||||
| Hospital-acquired pneumonia | No evidence availabile | ||||||||||||||||
| Ran et al | 2018 | Systematic review and meta-analysis | Inception to March 2018 | randomised controlled trials | PubMed, Cochrane Library, Elsevier, CNKI, VIP databases, WANFANG | vitamin C, added as a regular supplement or administered as needed when cold symptoms developed | definitive diagnosis of common cold based on laboratory examination, clinical signs, or reported symptoms; no limitation in age, sex, occupation | 9 | 9 x randomised placebo-controlled trials | Oral | n = 5722 + 1 study n = not reported | from 0.67 g per 4 h (4 g over 24 h) to max 10 doses; 1500 mg on day 1 after 500 mg/day; max8 g on day 1 | all studies used unspecified placebo | Vit C 2564; control 2076; 1082 unspecified; 1 study not reported | Mean duration; nasal congestion or runny nose; sore throat; aching limbs and muscles; mental depression; | no statistical significance | |
| Fever | significantly better at reducing fever by about 0.5 days (MD = -0.45, 95 % CI [-0.78, -0.11], and P = 0.009) | ||||||||||||||||
| Chest pain | higher efficacy in relieving chest pain (MD = -0.40, 95 % CI [-0.77, -0.03], and P = 0.03) | ||||||||||||||||
| Chills | better at relieving chills by about 8.5 h (MD = -0.36, 95% CI [-0.65, -0.07], and P = 0.01) | ||||||||||||||||
| Being confined Indoors | reduced confinement indoors by about 6.5 h (MD = -0.27, 95% CI [-0.46, -0.08], and P = 0.004) | ||||||||||||||||
| Zhang and Jativa | 2018 | Excluded as participant did not have ARI | |||||||||||||||
| Heimer | 2009 | Excluded as it is a review of reviews | |||||||||||||||
| Hemila | 1994 | Excluded as superceded by Hemila 2013 | |||||||||||||||
| Hemila | 1999 | Excluded as supplementation was initiated with healthy subjects | |||||||||||||||
| Nahas and Balla | 2011 | Excluded as the vitamin C part was a review of reviews | |||||||||||||||
| Rondanelli et al | 2018 | Excluded as it is a narrative review | |||||||||||||||