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Post-Diagnosis use of Antioxidant Vitamin Supplements and Breast Cancer Prognosis: A Systematic Review and Meta-Analysis.
Li, Y, Lin, Q, Lu, X, Li, W
Clinical breast cancer. 2021;(6):477-485
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Abstract
Antioxidant vitamin supplements (AVSs) are widely used among breast cancer survivors. Whether post-diagnosis use of AVSs would impair cancer survival is unclear. To assess the association between breast cancer survival and post-diagnosis AVSs use. We performed a literature search using PubMed, Cochrane Library, and Embase from their inception to October 1, 2020. Studies that investigated the association between breast cancer survival and post-diagnosis AVS use included. The AVSs included 1 or more of the following: vitamin A, C, or E. The meta-analysis included 8 studies with 17,062 patients. There was no significant difference between AVS use or not after diagnosis (HR 0.92, 95% CI 0•82-1•03) or during chemotherapy (HR 1.15, 95% CI 0.78-1.68) in overall survival (OS). Whenever during chemotherapy or after diagnosis, AVS users had a worse prognosis in the later studies. There was no significant inverse association between post-diagnosis vitamin A or E supplements use and OS. Vitamin C intake after breast cancer diagnosis was significantly associated with better OS (HR 0.84, 95% CI 0.76-0.93). Our findings suggest that post-diagnosis AVSs use would not worsen breast cancer survival, while vitamin C use after diagnosis might benefit OS. The discrepancy of survivals associated with post-diagnosis AVS use between earlier and later studies may cast doubt on the recommendation on guidelines. RCTs with large sample sizes are needed.
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Effect of dietary vitamins C and E on the risk of Parkinson's disease: A meta-analysis.
Chang, MC, Kwak, SG, Kwak, S
Clinical nutrition (Edinburgh, Scotland). 2021;(6):3922-3930
Abstract
BACKGROUND & AIMS A neuroprotective effect of dietary vitamins C and E on Parkinson's disease (PD) has been suggested, however, several human studies have reported controversial results. Therefore, we conducted a meta-analysis on the effect of vitamins C and E on the risk of Parkinson's disease. METHODS A comprehensive literature search was conducted using the PubMed, EMBASE, Cochrane Library, and SCOPUS databases for studies published up to January 23, 2021. We included studies that reported (1) intake of vitamins C and E using validated methods; (2) assessment of odds ratio (OR), relative risk (RR), or hazard ratio (HR); and (3) patients with PD identified by a neurologist, hospital records, or death certificates. The Comprehensive Meta-Analysis Software 2 program was used for statistical analyses of the pooled data. RESULTS A total of 12 studies (four prospective cohort and eight case-control studies) were included in our meta-analysis. No significant risk reduction was observed in the high vitamin C intake group compared to low intake group. On the other hand, the high vitamin E intake group showed a significantly lower risk of development of PD than the low intake group (pooled OR = 0.799. 95% CI = 0.721 to 0.885). CONCLUSIONS We conclude that vitamin E might have a protective effect against PD, while vitamin C does not seem to have such an effect. However, the exact mechanism of the transport and regulation of vitamin E in the CNS remains elusive, and further studies would be necessary in this field.
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Vitamin C in Critically Ill Patients: An Updated Systematic Review and Meta-Analysis.
Shrestha, DB, Budhathoki, P, Sedhai, YR, Mandal, SK, Shikhrakar, S, Karki, S, Baniya, RK, Kashiouris, MG, Qiao, X, Fowler, AA
Nutrients. 2021;(10)
Abstract
BACKGROUND Vitamin C is a water-soluble antioxidant vitamin. Oxidative stress and its markers, along with inflammatory markers, are high during critical illness. Due to conflicting results of the published literature regarding the efficacy of vitamin C in critically ill patients, and especially the concerns for nephrotoxicity raised by some case reports, this meta-analysis was carried out to appraise the evidence and affirmation regarding the role of vitamin C in critically ill patients. METHODS We searched the database thoroughly to collect relevant studies that assessed intravenous vitamin C use in critically ill patients published until 25 February 2021. We included randomized controlled trials and observational studies with 20 or more critically ill patients who have received intravenous ascorbic acid (vitamin C). After screening 18,312 studies from different databases, 53 were included in our narrative synthesis, and 48 were included in the meta-analysis. We used the Covidence software for screening of the retrieved literature. Review Manager (RevMan) 5.4 was used for the pooling of data and Odds Ratios (OR) and Mean difference (MD) as measures of effects with a 95% confidence interval to assess for explanatory variables. RESULTS Pooling data from 33 studies for overall hospital mortality outcomes using a random-effect model showed a 19% reduction in odds of mortality among the vitamin C group (OR, 0.81; 95% CI, 0.66-0.98). Length of hospital stay (LOS), mortality at 28/30 days, ICU mortality, new-onset AKI and Renal Replacement Therapy (RRT) for AKI did not differ significantly across the two groups. Analysis of data from 30 studies reporting ICU stay disclosed 0.76 fewer ICU days in the vitamin C group than the placebo/standard of care (SOC) group (95% CI, -1.34 to -0.19). This significance for shortening ICU stay persisted even when considering RCTs only in the analysis (MD, -0.70; 95% CI, -1.39 to -0.02). CONCLUSION Treatment of critically ill patients with intravenous vitamin C was relatively safe with no significant difference in adverse renal events and decreased in-hospital mortality. The use of vitamin C showed a significant reduction in the length of ICU stays in critically ill patients.
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Vitamin C and COVID-19 treatment: A systematic review and meta-analysis of randomized controlled trials.
Rawat, D, Roy, A, Maitra, S, Gulati, A, Khanna, P, Baidya, DK
Diabetes & metabolic syndrome. 2021;(6):102324
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BACKGROUND AND AIMS Vitamin C has been used as an anti-oxidant in various diseases including viral illnesses like coronavirus disease (COVID-19). METHODS Meta-analysis of randomized controlled trials (RCT) investigating the role of vitamin C supplementation in COVID-19 was carried out. RESULTS Total 6 RCTs including n = 572 patients were included. Vitamin C treatment didn't reduce mortality (RR 0.73, 95% CI 0.42 to 1.27; I2 = 0%; P = 0.27), ICU length of stay [SMD 0.29, 95% CI -0.05 to 0.63; I2 = 0%; P = 0.09), hospital length of stay (SMD -0.23, 95% CI -1.04 to 0.58; I2 = 92%; P = 0.57) and need for invasive mechanical ventilation (Risk Ratio 0.93, 95% CI 0.61 to 1.44; I2 = 0%; P = 0.76). Further sub-group analysis based on severity of illness (severe vs. non-severe), route of administration (IV vs. oral) and dose (high vs. low) failed to show any observable benefits. CONCLUSION No significant benefit noted with vitamin C administration in COVID-19. Well-designed RCTs with standardized control group needed on this aspect.
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Effects of vitamin C supplementation on essential hypertension: A systematic review and meta-analysis.
Guan, Y, Dai, P, Wang, H
Medicine. 2020;(8):e19274
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BACKGROUND Vitamin C as a supplement to treat hypertension has been proposed. However, it remains controversial whether vitamin C can improve blood pressure in patients with primary hypertension. OBJECTIVES To analyze the effect of vitamin C (VitC) supplementation on systolic (SBP) and diastolic (DBP) blood pressure in patients with essential hypertension. METHODS We searched the Chinese Knowledge Infrastructure, VIP Database for Chinese Technical Periodicals, WANFANG Data, Cochrane Library, National Library of Medicine's PubMed, EMBASE, and other databases until June 2019. Eight RCTs involving 614 participants were analyzed. SBP and DBP before and after VitC supplementation were compared between the intervention and control groups. The risk of bias of individual studies was assessed using the Cochrane Collaboration risk of bias tool. Two reviewers selected studies independently of each other. The Cochrane Collaboration Review Manager 5.3 was used to perform the meta-analysis. RESULTS There was a significant difference in the change of SBP (weighted mean difference [WMD] = -4.09; 95% confidence interval [CI] -5.56, -2.62; P < .001) and DBP (WMD = -2.30; 95% CI -4.27, -.331; P = .02) between the groups. Further, there was a significant difference in the SBP (WMD = -3.75, 95% CI -6.24, -1.26, P = .003) and DBP (WMD = -3.29, 95% CI -5.98, -.60, P = .02) for the subgroup with an age ≥60 years and that with ≥35 participants. In the subgroup analysis, result for SBP with a study duration ≥6 weeks was statistically significant different (WMD = -4.77; 95% CI -6.46, -3.08; P < .001). For an intervention dose of VitC ≥500 mg daily, SBP was statistically significant (WMD = -5.01; 95% CI -8.55, -1.48; P = .005). CONCLUSION VitC supplementation resulted in a significant reduction of blood pressure in patients with essential hypertension.
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Vitamin C as a Supplementary Therapy in Relieving Symptoms of the Common Cold: A Meta-Analysis of 10 Randomized Controlled Trials.
Ran, L, Zhao, W, Wang, H, Zhao, Y, Bu, H
BioMed research international. 2020;:8573742
Abstract
AIM: To investigate whether vitamin C performs well as a supplemental treatment for common cold. METHOD After systematically searching through the National Library of Medicine (PubMed), Cochrane Library, Elsevier, China National Knowledge Infrastructure (CNKI), VIP databases, and Wanfang databases, 10 randomized controlled trials were selected for our meta-analysis with RevMan 5.3 software. Published in China, all 10 studies evaluated the effect of combined vitamin C and antiviral therapy for the treatment of common cold. RESULTS The total efficacy (RR = 1.27, 95% CI (1.08, 1.48), P = 0.003), the time for symptom amelioration (MD = -15.84, 95% CI (-17.02, -14.66), P < 0.00001), and the time for healing (I, 95% CI (-14.98, -4.22), P = 0.0005) were better with vitamin C supplementation than with antiviral therapy alone. CONCLUSIONS Vitamin C could be used as a supplementary therapy along with antiviral regimens to relieve patients from the symptoms of common cold.
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Dietary and circulating vitamin C, vitamin E, β-carotene and risk of total cardiovascular mortality: a systematic review and dose-response meta-analysis of prospective observational studies.
Jayedi, A, Rashidy-Pour, A, Parohan, M, Zargar, MS, Shab-Bidar, S
Public health nutrition. 2019;(10):1872-1887
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OBJECTIVE The present review aimed to quantify the association of dietary intake and circulating concentration of major dietary antioxidants with risk of total CVD mortality. DESIGN Systematic review and meta-analysis. SETTING Systematic search in PubMed and Scopus, up to October 2017.ParticipantsProspective observational studies reporting risk estimates of CVD mortality across three or more categories of dietary intakes and/or circulating concentrations of vitamin C, vitamin E and β-carotene were included. A random-effects meta-analysis was conducted. RESULTS A total of fifteen prospective cohort studies and three prospective evaluations within interventional studies (320 548 participants and 16 974 cases) were analysed. The relative risks of CVD mortality for the highest v. the lowest category of antioxidant intakes were as follows: vitamin C, 0·79 (95 % CI 0·68, 0·89; I 2=46 %, n 10); vitamin E, 0·91 (95 % CI 0·79, 1·03; I 2=51 %, n 8); β-carotene, 0·89 (95 % CI 0·73, 1·05; I 2=34 %, n 4). The relative risks for circulating concentrations were: vitamin C, 0·60 (95 % CI 0·42, 0·78; I 2=65 %, n 6); α-tocopherol, 0·82 (95 % CI 0·76, 0·88; I 2=0 %, n 5); β-carotene, 0·68 (95 % CI 0·52, 0·83; I 2=50 %, n 6). Dose-response meta-analyses demonstrated that the circulating biomarkers of antioxidants were more strongly associated with risk of CVD mortality than dietary intakes. CONCLUSIONS The present meta-analysis demonstrates that higher vitamin C intake and higher circulating concentrations of vitamin C, vitamin E and β-carotene are associated with a lower risk of CVD mortality.
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The Effect of Vitamin C on Clinical Outcome in Critically Ill Patients: A Systematic Review With Meta-Analysis of Randomized Controlled Trials.
Putzu, A, Daems, AM, Lopez-Delgado, JC, Giordano, VF, Landoni, G
Critical care medicine. 2019;(6):774-783
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OBJECTIVES The effects of vitamin C administration on clinical outcome in critically ill patients remain controversial. DATA SOURCES Online databases were searched up to October 1, 2018. STUDY SELECTION We included randomized controlled trials on the use of vitamin C (any regimen) in adult critically ill patients versus placebo or no therapy. DATA EXTRACTION Risk ratio for dichotomous outcome and standardized mean difference for continuous outcome with 95% CI were calculated using random-effects model meta-analysis. DATA SYNTHESIS Forty-four randomized studies, 16 performed in ICU setting (2,857 patients) and 28 in cardiac surgery (3,598 patients), published between 1995 and 2018, were included in the analysis. In ICU patients, vitamin C administration was not associated with a difference in mortality (risk ratio, 0.90; 95% CI, 0.74-1.10; p = 0.31), acute kidney injury, ICU or hospital length of stay compared with control. In cardiac surgery, vitamin C was associated to a reduction in postoperative atrial fibrillation (risk ratio, 0.64; 95% CI, 0.52-0.78; p < 0.0001), ICU stay (standardized mean difference, -0.28 d; 95% CI, -0.43 to -0.13 d; p = 0.0003), and hospital stay (standardized mean difference, -0.30 d; 95% CI, -0.49 to -0.10 d; p = 0.002). Furthermore, no differences in postoperative mortality, acute kidney injury, stroke, and ventricular arrhythmia were found. CONCLUSIONS In a mixed population of ICU patients, vitamin C administration is associated with no significant effect on survival, length of ICU or hospital stay. In cardiac surgery, beneficial effects on postoperative atrial fibrillation, ICU or hospital length of stay remain unclear. However, the quality and quantity of evidence is still insufficient to draw firm conclusions, not supporting neither discouraging the systematic administration of vitamin C in these populations. Vitamin C remains an attractive intervention for future investigations aimed to improve clinical outcome.
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Vitamin C Administration to the Critically Ill: A Systematic Review and Meta-Analysis.
Langlois, PL, Manzanares, W, Adhikari, NKJ, Lamontagne, F, Stoppe, C, Hill, A, Heyland, DK
JPEN. Journal of parenteral and enteral nutrition. 2019;(3):335-346
Abstract
Vitamin C, an enzyme cofactor and antioxidant, could hasten the resolution of inflammation, oxidative stress, and microvascular dysfunction. While observational studies have demonstrated that critical illness is associated with low levels of vitamin C, randomized controlled trials (RCTs) of vitamin C, alone or in combination with other antioxidants, have yielded contradicting results. We searched MEDLINE, EMBASE, CINAHL, and the Cochrane Central Register of Controlled Trials (inception to December 2017) for RCTs comparing vitamin C, by enteral or parenteral routes, with placebo or none, in intensive care unit (ICU) patients. Two independent reviewers assessed study eligibility without language restrictions and abstracted data. Overall mortality was the primary outcome; secondary outcomes were incident infections, ICU length of stay (LOS), hospital LOS, and duration of mechanical ventilation (MV). We prespecified 5 subgroups hypothesized to benefit more from vitamin C. Eleven randomized trials were included. When 9 RCTs (n = 1322) reporting mortality were pooled, vitamin C was not associated with reduced risk of mortality (risk ratio [RR] 0.72, 95% confidence interval [CI]: 0.43-1.20, P = .21). No effect was found on infections, ICU or hospital LOS, or duration of MV. In multiple subgroup comparison, no statistically significant subgroup effects were observed. However, we did observe a tendency towards a mortality reduction (RR 0.21; 95% CI: 0.04-1.05; P = .06) when intravenous high-dose vitamin C monotherapy was administered. Current evidence does not support supplementing critically ill patients with vitamin C. A moderately large treatment effect may exist, but further studies, particularly of monotherapy administration, are warranted.
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Ascorbic Acid Supplements and Kidney Stones Incidence Among Men and Women: A systematic review and meta-analysis.
Jiang, K, Tang, K, Liu, H, Xu, H, Ye, Z, Chen, Z
Urology journal. 2019;(2):115-120
Abstract
PURPOSE The relationship of ascorbic acid (AA) supplements and risk of kidney stones among men and women is controversial. This systematic evaluation was performed to obtain comprehensive evidence about the relationship of AA supplements and risk of kidney stones among men and women. MATERIAL AND METHODS A systematic search of Pubmed, the Cochrane Library, Web of Science, Embase was performed to identify studies that exhibited the relationship of AA supplements and risk of kidney stones among men and women were published up to Mar 2017. Outcomes of interest included kidney stones incidence and risk factors. RESULTS Four studies estimating the association between AA supplements and risk of kidney stones were included for meta-analysis. The kidney stones incidence was significantly higher in men than women with AA supplements (OR= 1.62; 95% CI: 1.09 to 2.42; P=0.02). AA supplements (250-499mg/d, 1000-1499mg/d) was remarkably correlated with the risk of renal stones among men (OR= 1.14, 95% CI: 1.00 to 1.28, P=0.04; OR= 1.12, 95% CI: 1.11 to 1.13, P<0.00001; respectively). However, AA supplements (500-999 mg/d, >1500 mg/d) did not correlate with the risk of renal stones among men (OR= 1.20, 95% CI: 0.99 to 1.46, P=0.06; OR= 1.28, 95% CI: 1.00 to 1.63, P= 0.05; respectively). In addition, AA supplements (250-499mg/d, 500-999mg/d, 1000-1499mg/d, >1500mg/d) did not remarkably correlate with the risk of renal stones among women (OR= 1.00, 95% CI: 0.82 to 1.22, P=0.98; OR= 1.08, 95% CI: 0.99 to 1.18, P=0.09; OR= 0.99, 95% CI: 0.90 to 1.08, P=0.77; OR= 0.99, 95% CI: 0.99 to 1.09, P=0.88; respectively). CONCLUSIONS AA supplements was remarkably correlated with higher risk for kidney stones incidence in men, but not in women. Further multicenter, prospective and long-term follow-up RCTs are required to verify these findings.