# Talk:Vitamin C

I nominated for Featured Article on 20 December 2023, but the initial evaluation identified too many shortfalls to start the process, so application was reverted. Have not decided yet whether to burnish the article and try again or let it remain as a Good Article which I watch and try to keep current as new research is published. David notMD (talk) 00:24, 21 December 2023 (UTC)

Revising content, including Lead, for clarity of language, less redundancy, etc. Also checking refs to confirm what is in refs validates text. Preference, but not an absolute requirement, will be to refs that are available online. David notMD (talk) 14:56, 24 December 2023 (UTC)
Will submit for Peer review before resubmitting for FA. David notMD (talk) 19:15, 5 January 2024 (UTC)
Submitted for Peer review 9 January. David notMD (talk) 13:12, 18 January 2024 (UTC)
Continuing evaluation of quality of references, including replacing those that are not WP:MEDRS or are journal article refs more than 20 years old that can be replaced by newer refs. David notMD (talk) 13:12, 18 January 2024 (UTC)
Nominated a second time on 8 February 2024. David notMD (talk) 04:39, 9 February 2024 (UTC)

Just had a quick look. A lot of the sourcing is old, and throughout WP:MEDSAY is not observed with a lot of "A meta-analysis said .." type wording. Bon courage (talk) 05:14, 9 February 2024 (UTC)
Bon courage I will address MEDSAY throughout. Some of the sourcing relates to history and discovery, so 'old' is appropriate. For everything else, is there a year you consider the dividing line between old and appropriate? David notMD (talk) 19:29, 9 February 2024 (UTC)
WP:MEDDATE says 5 years. A PubMed search using the terms "systematic review meta-analysis" gives 327 articles, the best of which are already included. This search found several MDPI publications which should be scrutinized.
When "Cochrane" is added as a search term, 194 articles are retrieved, but with MDPI and Cureus hits (should be avoided). In the article, there are numerous Nutrients (MDPI) sources, which may be predatory, and should be replaced if a better review exists for the FA.
I use the "unreliable" script ('User:Headbomb/unreliable.js'); which paints sources that deserve a second look. There are several dozen of these in the article. Zefr (talk) 20:27, 9 February 2024 (UTC)
Zefr I will review references with WP:MEDDATE, MDPI journals and the journal Nutrients in particular, in mind. Most of the references of concern appear to be in the sections Deficiency, Medical uses and Adverse (#19-81). That includes Nutrients refs 24, 36, 64, 68 & 79. If, for example, the article cites multiple meta-analyses in support of content, I will remove the older or MDPI if the newer is of same or better quality (for example, incorporates a larger number of clinical trials).
I am not familiar with using the "unreliable" script, so I may ask for guidance before implementing that. Thank you for your comments. David notMD (talk) 12:30, 10 February 2024 (UTC)
I think it was mostly the cancer sources which seemed old (I updated a couple); otherwise this does not seem a big issue now. Bon courage (talk) 14:28, 11 February 2024 (UTC)
Nutrients journal refs now numbered 27 Xu, 39 Olczak, 56 Pullar, 72 Shrestha and 116 Lykkesfeldf. I will check at PubMed to find out if other ref options possible. David notMD (talk) 04:45, 12 February 2024 (UTC)
The FA nomination process ended on 1 March with a not accepted. David notMD (talk) 22:43, 1 March 2024 (UTC)

For what little it's worth, I think this article is incredibly lopsided- almost entirely human-centric, more appropriate for a medical encyclopedia.  For example, I came here to learn what purpose Vitamin C serves to fruit- its natural source- and it's buried toward the bottom of the page. Even the Infobox leads with legal and pharmacological data before finally getting to chemistry and physical data at the very bottom- which apparently needs verification?     2601:249:9381:4840:B389:A2A3:6EF0:AC19 (talk) 16:56, 5 October 2025 (UTC)

https://www.ncbi.nlm.nih.gov/books/NBK230149/ shows up as a 53.4% Violation possible because there is a quote or several sentences - referenced - in the Food Fortification section.
https://www.nap.edu/read/9810/chapter/7 Vitamin C shows up as a 51.0% Violation possible because in Adverse effects section, two sentences are quoted (and referenced), plus there are many very short sections of text common to the reference and the article
http://lpi.oregonstate.edu/mic/vitamins/vitamin-C Linus Pauling Institute shows up as a 41.2% Violation possible because there are many very short sections of text common to both
https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/ NIH Fact sheet shows up as a 37.5% Violation possible because there are many very short sections of text common to both
So, 1 and 2 are for referenced quotes, and 2, 3 & 4 are for many very short sections of text David notMD (talk) 23:51, 18 January 2024 (UTC)

Checked again on 24 February. For same sources and reasons as above:
https://www.ncbi.nlm.nih.gov/books/NBK230149/ now showing up as a 53.1% Violation
https://www.nap.edu/read/9810/chapter/7 now showing up as 56.1% Violation
http://lpi.oregonstate.edu/mic/vitamins/vitamin-C now showing up as a 39.8% Violation
https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/ now showing up as a 36.3% Violation
My evaluation is that none of these are a true copyright violation. David notMD (talk) 13:32, 24 February 2024 (UTC)

The FA nomination review, after three weeks of comments from reviewers, and responses, ended 1 March with the nomination not being accepted. David notMD (talk) 22:45, 1 March 2024 (UTC)

Hello, @David notMD!
I think that we should add more information that is easier to understand on vitamin C oral absorption, and, in particular, on its limits. Although there is already the information in the article, it is not that easy to undertand. It is not that clear in the article. We write the encyclopedia for as wide audience as possible, and we should make it clear that the fact that a person drinks a vitamin C solution or tablets (capsules) does not mean that it will be absorbed. 
The following quotes from PMID 31601028 may be a starting point:

"vitC is predominantly represented by its anionic form (>99.9%) at neutral pH and is highly water-soluble. As such, it will only be able to diffuse across the plasma membrane at a relatively slow rate even in the presence of a considerable concentration gradient"
"Increasing oral doses were shown to lead to decreasing absorption fractions and it was concluded by several authors that intestinal ASC absorption is subject to saturable active transport"
"Ingested vitamin C (vitC) is absorbed across the intestinal epithelium primarily by membrane transporters in the apical brush border membrane, either as ascorbate (ASC) by sodium-coupled active transport via the SVCT1 transporter or as dehydroascorbic acid (DHA) through facilitated diffusion via GLUT1 or GLUT3 transporters. Once inside the cell, DHA is efficiently converted to ASC or transported to the blood stream by GLUT1 and GLUT2 in the basolateral membrane, hereby maintaining a low intracellular concentration and facilitating further DHA uptake. ASC is conveyed to plasma by diffusion, possibly also by facilitated diffusion through volume-sensitive anion channels or by yet unidentified active transporters; the precise efflux mechanisms remain unknown.
Although these qoutes may be useful as a starting point, I guess we should try to explain in simple words on how much is absorbed, say, for a dose of 200 mg, 1000 mg, 2000 mg, 10000 mg per day / per dose and so on. Maxim Masiutin (talk) 17:25, 29 April 2024 (UTC)

I agree that the oral absorption portion can benefit from starting with a simple summary-type sentence. The gist needs to be that once the active transport system is saturated the percent being absorbed drops off dramatically as the amount consumed increases even though the amount being absorbed continues to increase. David notMD (talk) 18:20, 29 April 2024 (UTC)
Yes, you made a good point. However, the paradox may be that even the the amount being absorbed may decrease at some point, as reverse osmosis sucks water from blood to intestine to dissolve high concentration of acid to protect epithelium from chemical acid burns, which lead to diarea-like symptoms which is actually water from blood dissolved ascorbic acid, although I didn't find a reliable source; but it probably starts from a dose of 6 grams one-time oral dose. If you will find something like that, it is probably worth mentioning. Maxim Masiutin (talk) 22:48, 29 April 2024 (UTC)
I saw another study (don't find it right now) that from a certain point, oral dose increase do not lead to plasma increase, suggesting that oral absorption stops altogether from a certain point of dosage, confirming my point about reverse osomosis protection mechanism. Maxim Masiutin (talk) 22:50, 29 April 2024 (UTC)
We currently have a section "Pharmacokinetics" which describes basic mechanisms quite well, but my suggestion is to add basic information into this section to make easier to understand for wide audience (normal people) on what actually happens with oral absorption amounts. Maxim Masiutin (talk) 22:52, 29 April 2024 (UTC)

I removed "more research is needed" or "further research is needed" or similar cliches, and, as a consistence, move all the poorly sourced claims which are subject of ongoing research to a separate "Research directions" section, see Further research is needed. I may have not moved all such "more research is needed" claims as I might have overlooked something, but I strongly encourage doing that way to avoid "more research is needed"-related statements in the main article and use a separate section instead to distinguish clearly the strong claims from poor claims which are the subject of ongoing research or when the evidence is poor. Maxim Masiutin (talk) 23:06, 29 April 2024 (UTC)

I propose to resolve vague statements about "claims", in particular, the following statements:

Various health claims exist on the basis that moderate vitamin C deficiency increases disease risk, such as for the common cold, cancer or COVID-19.
There are also claims of benefits from vitamin C supplementation in excess of the recommended dietary intake for people who are not considered vitamin C deficient.
Such statements are perplexing because it is unclear whether these claims are substantiated. If they are unsubstantiated, I propose to rewrite the following way:

Various unsubstantiated health claims exist on the basis that moderate vitamin C deficiency increases disease risk, such as for the common cold, cancer or COVID-19.
There are also unsubstantiated claims of benefits from vitamin C supplementation in excess of the recommended dietary intake for people who are not considered vitamin C deficient.
If these claims are substantiated, then I propose to rewrite the sentences to simply state the facts rather than referring to them as claims:

Moderate vitamin C deficiency was proven to increases disease risk, such as for the common cold, cancer or COVID-19.
There are proven benefits from vitamin C supplementation in excess of the recommended dietary intake for people who are not considered vitamin C deficient.
We have to write Wikipedia articles to be easy to understand, so when a reader finds the words "claims" such reader should not be forced to search sources to figure out whether these claims are true or false or are a point of debate. Maxim Masiutin (talk) 01:55, 2 May 2024 (UTC)

My opinion is that these unreferenced statements as written in the Lead do not need to be change in the Lead because there are referenced subsections in the Medical uses section that explain at length why these claims exist and the current lack of quality research in support. The context is that for vitamin C (and for other nutrients - see vitamin E and vitamin D) there is a history of conflicting science evidence in the science journal literature, but that at present, the consensus is that the proposed benefits for vitamin C (cold, cancer, COVID) are not confirmed. Despite this, the fact that popular belief 'got out over the tips of the skis' is framed in the existing text, as "Various health claims exist..." conveys the claims/confirmation discord. A last point - clinical trial research continues in these areas, so at some point in the future the weight of evidence may shift to support of the claims. David notMD (talk) 10:01, 4 May 2024 (UTC)
I don't mean references, I mean the vagueness of the text. According to MOS:LEAD, the text in the lead should be self-containing and clear enough without the need to read the body to address vagueness in the lead, as most readers only read the lead, so the information in the lead should be clear in isolation from the rest of the article. The statement that "Various health claims exist..." conveys the claims/confirmation discord is questionable, as English Wikipedia is read not only by the native English speakers, so we should be explicit enough. Maxim Masiutin (talk) 17:03, 5 May 2024 (UTC)