Recently I suggested one approach to check a claim was to look to the review literature. That article was a generalisation of what I originally wrote as a comment in reply to others’ claim that high-dose intravenous (IV) vitamin C was a sound treatment for severe pneumonia. Below is a revised and expanded version of the comment as a worked example of using this approach, followed by a brief round-out
My article was about local media coverage of a family that insisted high-dose intravenous vitamin C be used on their critically ill relative. (Note: not the science, nor the politics for that matter.)
A wide range of claims were made supporting the use of this treatment, on my blog and elsewhere, with some writers extending it out to wider applications.
Let’s use an examination of the claim that intravenous vitamin C is a sound treatment for severe pneumonia as a worked example of using the review literature to investigate the soundness a claim.*
I can serve as the non-specialist seeking to check a claim, in this case one made by others. (While I have the advantage of knowing how the research literature works and biology background in other areas, the biology of vitamin C and practical medicine are not areas I cover.)
A PubMed search using the keywords ‘vitamin C pneumonia review’ reports twelve review articles. These keywords are intentionally broad: in practice we’re after intravenous treatments of high doses of vitamin C in late stage severe pneumonia cases: using broader keywords means you’re less likely to miss anything. It also lets me do a one-pass search. Here’s what this search gives us:
- Malacoplakia presenting with obstructive nephropathy with bilateral ureter involvement. Sanchez LM, Sanchez SI, Bailey JL. Nat Rev Nephrol. 2009 Jul;5(7):418-22. Review. PMID: 19556995
- The autoimmune disease complex interstitial pneumonia/dermatomyositis in the light of endocrinology and cancer epidemiology. Kodama M, Kodama M. In Vivo. 2009 Mar-Apr;23(2):353-6. Review. PMID: 19414426
- Control of interstitial pneumonia by drip infusion of megadose vitamin C, dehydroepiandrosterone and cortisol. A short review of our experience. Kodama M, Oyama A, Takagi H. In Vivo. 2008 Mar-Apr;22(2):263-7. Review. PMID: 18468413
- Vitamin C may affect lung infections. HemilÃ¤ H, Louhiala P. J R Soc Med. 2007 Nov;100(11):495-8. Review. No abstract available. PMID: 18048704
- Vitamin C for preventing and treating pneumonia. HemilÃ¤ H, Louhiala P. Cochrane Database Syst Rev. 2007 Jan 24;(1):CD005532. Review. PMID: 17253561
- Immune-enhancing role of vitamin C and zinc and effect on clinical conditions. Wintergerst ES, Maggini S, Hornig DH. Ann Nutr Metab. 2006;50(2):85-94. Epub 2005 Dec 21. Review. PMID: 16373990
- History of evidence-based medicine. Oranges, chloride of lime and leeches: barriers to teaching old dogs new tricks. Doherty S. Emerg Med Australas. 2005 Aug;17(4):314-21. PMID: 16091093
- Vitamin C supplementation and respiratory infections: a systematic review. HemilÃ¤ H. Mil Med. 2004 Nov;169(11):920-5. Review. PMID: 15605943
- Vitamin C and acute respiratory infections. HemilÃ¤ H, Douglas RM. Int J Tuberc Lung Dis. 1999 Sep;3(9):756-61. Review. PMID: 10488881
- Vitamin C intake and susceptibility to pneumonia. HemilÃ¤ H. Pediatr Infect Dis J. 1997 Sep;16(9):836-7. Review. No abstract available. PMID: 9306475
- Pneumonia in the elderly. Marrie TJ. Curr Opin Pulm Med. 1996 May;2(3):192-7. Review. PMID: 9363139
- [Role of thymus gland in childhood diseases] Petriaeva AT, Kulagina LV, Kostiuchenkova VN. Vopr Okhr Materin Det. 1975 Nov;20(11):49-53. Review. Russian. No abstract available. PMID: 769330
Of the twelve articles found, three are clearly irrelevant from the titles (1,2, 12). Keyword searches almost always throw up false-positives, so this isn’t surprising.
Another is a philosophical commentary (7), leaving us with eight. As one author has repeatedly published on the topic, giving us four hopefully independent authors (nonetheless I’ve looked at all eight remaining articles). At least one has a potential conflict of interest (6, commercial). One deals with a target group that isn’t the target group in question (the elderly, 11).
I’m going to limit myself to the abstracts. I haven’t time to do more, and the point of this isn’t to do an in-depth analysis, but to illustrate querying the general state of a field from a precursory and high-level peek.
Two of the review articles (4, 10) lack abstracts. (Lack of abstracts is more common for smaller journals that don’t provide abstracts to PubMed, or for letters to the editor. I haven’t time to muck around looking at each journal’s web page. In any event, the two ‘missing’ abstracts are from the same author that I have four to read.)
Of those articles that I can access abstracts of, none refer to severe pneumonia or late stage treatment. Most refer to preventative supplementation in the infirm (e.g. elderly), the physically stressed (e.g. military, marathon runners), or those with known deficiency.
While this is hardly conclusive (it’s only a few minutes skimming), it is suggestive. It would suggest that there is no established conclusion on the use of IV vitamin C in severe cases of pneumonia.
There are one or two research papers (as opposed to the reviews I am looking at here) that might deserve a closer reading if the topic was of deep interest (i.e. to an academic researcher in the area), but there would seem to be no indication that this field has a firm widely-accepted conclusion.
It would be very surprising not to find a review article on this topic if there were an established conclusion, given the attention it would bring.
I think, in the absence of a deeper knowledge of the niche area of science, the fairest conclusion would then be that it is unlikely there is an agreed consensus to use of IV vitamin C for severe pneumonia at least in the review literature (my brief skim suggests there is no review concluding this at all).
* I am not offering this as a definitive statement about this treatment, as I would think is clear from the article.
Other articles in Code for life: