Abstract
Background: Respiratory tract infections are a primary cause of illness and mortality over the world.
Objective : This study was aimed to investigate the effectiveness of vitamin C supplementation in preventing and treating respiratory tract infections.
Methods: We used the Cochrane, PubMed, and MEDLINE Ovid databases to conduct our search. The inclusion criteria were placebo-controlled trials. Random effects meta-analyses were performed to measure the pooled effects of vitamin C supplementation on the incidence, severity, and duration of respiratory illness.
Results : We found ten studies that met our inclusion criteria out of a total of 2758. The pooled risk ratio (RR) of developing respiratory illness when taking vitamin C regularly across the study period was 0.94 (with a 95% confidence interval of 0.87 to 1.01) which found that supplementing with vitamin C lowers the occurrence of illness. This effect, however, was statistically insignificant (P= 0.09). This study showed that vitamin C supplementation had no consistent effect on the severity of respiratory illness (SMD 0.14, 95% CI -0.02 to 0.30: I2 = 22%, P=0.09). However, our study revealed that vitamin C group had a considerably shorter duration of respiratory infection (SMD -0.36, 95% CI -0.62 to -0.09, P = 0.01).
Conclusion: Benefits of normal vitamin C supplementation for reducing the duration of respiratory tract illness were supported by our meta-analysis findings. Since few trials have examined the effects of therapeutic supplementation, further research is needed in this area.
Keywords: Ascorbic acid , immunity, efficacy, incidence, severity, respiratory illness .
[PMID: 16536953]
[http://dx.doi.org/10.1007/s100960050161] [PMID: 9865980]
[http://dx.doi.org/10.1007/978-1-59745-464-3_7]
[http://dx.doi.org/10.1017/S0007114507832971] [PMID: 17922955]
[http://dx.doi.org/10.3390/nu9111211] [PMID: 29099763]
[http://dx.doi.org/10.1007/978-3-030-16073-9_5]
[http://dx.doi.org/10.1016/S0140-6736(00)04904-7] [PMID: 11403834]
[http://dx.doi.org/10.1007/978-3-030-26961-6_28]
[http://dx.doi.org/10.1016/j.eclinm.2021.100986] [PMID: 34386754]
[http://dx.doi.org/10.1371/journal.pmed.1003550] [PMID: 33647033]
[http://dx.doi.org/10.1177/014107680710001109] [PMID: 18048704]
[http://dx.doi.org/10.1002/14651858.CD013292]
[http://dx.doi.org/10.1136/bmjgh-2020-003176] [PMID: 33472840]
[http://dx.doi.org/10.1136/bmj.n71] [PMID: 33782057]
[http://dx.doi.org/10.1007/s11999-011-1908-9] [PMID: 21556923]
[http://dx.doi.org/10.1002/9780470712184]
[http://dx.doi.org/10.7326/0003-4819-149-12-200812160-00008] [PMID: 19075208]
[PMID: 4601508]
[PMID: 1091343]
[http://dx.doi.org/10.1136/jech.30.3.193] [PMID: 788820]
[PMID: 319446]
[http://dx.doi.org/10.1136/jech.31.3.189] [PMID: 338079]
[PMID: 7814237]
[http://dx.doi.org/10.1007/BF02850271] [PMID: 12201356]
[http://dx.doi.org/10.3390/nu6072572] [PMID: 25010554]
[http://dx.doi.org/10.1186/s13613-020-00792-3] [PMID: 33420963]
[http://dx.doi.org/10.1186/1471-2288-13-92] [PMID: 23855337]
[http://dx.doi.org/10.1017/S0022172400012596] [PMID: 20475613]
[http://dx.doi.org/10.1093/ajcn/32.8.1686] [PMID: 463806]
[http://dx.doi.org/10.1002/14651858.CD000980.pub4] [PMID: 23440782]
[http://dx.doi.org/10.1159/000090495] [PMID: 16373990]
[http://dx.doi.org/10.1155/2018/1837634] [PMID: 30069463]
[http://dx.doi.org/10.1001/jama.1979.03290350028016] [PMID: 368370]
[http://dx.doi.org/10.5867/medwave.2018.04.7236] [PMID: 30113569]
[http://dx.doi.org/10.1155/2020/8573742] [PMID: 33102597]
[http://dx.doi.org/10.1007/s12291-013-0375-3] [PMID: 24426232]
[http://dx.doi.org/10.1177/1559827616629092] [PMID: 30202272]
[PMID: 4920714]
[http://dx.doi.org/10.1001/jama.1975.03240220018013] [PMID: 163386]
[http://dx.doi.org/10.1017/S0007114500002889] [PMID: 9059230]