Vitamin C and asthma

by Harri Hemilä

Department of Public Health
University of Helsinki, Finland
harri.hemila@helsinki.fi
http://www.mv.helsinki.fi/home/hemila
Dec 14, 2017

  1. Original articles and systematic reviews

  2. Flaws in the Cochrane review on "vitamin C supplementation and asthma" (published in 2001 and withdrawn in 2013). The review had severe errors in extraction of data and in data analysis and misled readers for a decade.

  3. Letters and commentaries



Original articles and systematic reviews

Review on vitamin C and EIB, and a secondary analysis of a published study
Hemila H
The effect of vitamin C on bronchoconstriction and respiratory symptoms caused by exercise: a review and statistical analysis.
Allergy, Asthma & Clinical Immunology 2014;10:58
http://dx.doi.org/10.1186/1710-1492-10-58
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4363347 

Three studies found that vitamin C decreased common cold induced asthma exacerbations or bronchial hypersensitivity.
Hemila H
Vitamin C and common cold-induced asthma: a systematic review and statistical analysis.
Allergy, Asthma Clin Immunol 2013;9:46
http://dx.doi.org/10.1186/1710-1492-9-46
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4018579

Three studies found that vitamin C halved the FEV1 decline caused by exercise.
Hemila H
Vitamin C may alleviate exercise-induced bronchoconstriction: a meta-analysis.
BMJ Open 2013;3:e002416
http://dx.doi.org/10.1136/bmjopen-2012-002416
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3686214

Vitamin C was reported to alleviate asthma severity in Egyptian children, but the data set was found to be flawed.
Still the Egyptian study indicates that the effect of vitamin C should be further studied,
even though the validity of these particular findings is not clear.

Hemila H, Al-Biltagi M, Basset AA
Vitamin C and asthma in children: modification of the effect by age, exposure to dampness and the severity of asthma.
Clin Transl Allergy 2011;1:9
http://dx.doi.org/10.1186/2045-7022-1-9
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3339402
Retraction:
http://dx.doi.org/10.1186/2045-7022-2-6
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3320558
http://www.ncbi.nlm.nih.gov/pubmed/22423606
Postpublication problems: reasons for the retraction:
http://www.mv.helsinki.fi/home/hemila/PPH/CTA/CTA.html
See also
retraction of the initial publication on which the above 2011 subgroup analysis was based:
http://dx.doi.org/10.1111/j.1651-2227.2012.02723.x

Flaws in the Cochrane review on "vitamin C supplementation and asthma"
(published in 2001 and withdrawn in 2013).

The Cochrane review had severe errors in the extraction of data and in data analysis and misled readers for a decade.

Meta-analysis of 3 exercise-induced asthma trials and pointing out errors in the Cochrane review
This was expanded to BMJ Open paper in 2013, see above


Hemila H.
Feedback [Comments on the Cochrane review “vitamin C supplementation for asthma” by Kaur B, Rowe BH, Stovold E]
Cochrane Database of Systematic Reviews, Feedback 24 March 2009
https://helda.helsinki.fi/handle/10138/225865
https://helda.helsinki.fi/handle/10138/38500
http://dx.doi.org/10.13140/2.1.1280.3364
http://dx.doi.org/10.1002/14651858.CD000993.pub3

The above comment was submitted in 2009, but the authors replied no earlier than in 2012.
Furthermore, the reply was full of errors:

    Hemila H.
   
Vitamin C and exercise-induced bronchoconstriction:
    further problems in the Cochrane review "vitamin C for asthma" (2013).

    Unpublished commentary
    http://hdl.handle.net/10138/40816

The Cochrane review on vitamin C and asthma misled readers for a decade from 2001 to 2013.
See the PubMed records of the Cohrane review on vitamin C and asthma from 2001 to 2013:
http://www.ncbi.nlm.nih.gov/pubmed/11687089  
2001
http://dx.doi.org/10.1002/14651858.CD000993
http://www.ncbi.nlm.nih.gov/pubmed/11687089#cm11687089_9676

http://www.ncbi.nlm.nih.gov/pubmed/15266435  
2004
http://dx.doi.org/10.1002/14651858.CD000993.pub2

http://www.ncbi.nlm.nih.gov/pubmed/19160185  
2009
http://dx.doi.org/10.1002/14651858.CD000993.pub3
https://www.ncbi.nlm.nih.gov/pubmed/19160185#cm19160185_9685

http://www.ncbi.nlm.nih.gov/pubmed/24155047  
2013 Withdrawal of the Cochrane review
http://dx.doi.org/10.1002/14651858.CD000993.pub4

Letters and commentaries

Hemilä H. Evidence-based management of EIB with vitamin C
BMJ eLetter 29 Feb 2016
http://www.bmj.com/content/352/bmj.h6951/rr

Hemila H.
Vitamin C and asthma.
JACI 2014;134:1216
http://dx.doi.org/10.1016/j.jaci.2014.08.032

Hemila H. Vitamin C should be tested against exercise-induced bronchoconstriction.
AJRCCM 2013;188:1370
http://dx.doi.org/10.1164/rccm.201307-1205LE

Hemila H.
Vitamin C and exercise-induced bronchoconstriction in athletes.
JACI 2009:123:274-275
http://dx.doi.org/10.1016/j.jaci.2008.10.004