Talk:Vitamin C

Checking for newer meta-analyses and systematic reviews

Checking for relevant meta-analyses and systematic reviews published after this became a Good Article in late 2017. David notMD (talk) 04:18, 18 December 2023 (UTC)

Removed some of the Common cold subsection text and references and added a 2023 meta-analysis. David notMD (talk) 21:23, 18 December 2023 (UTC)

COVID-19 subsection replaced because of new references. David notMD (talk) 16:07, 18 December 2023 (UTC)

Added Type 2 diabetes subsection based on 2023 meta-analysis. David notMD (talk) 21:19, 18 December 2023 (UTC)

In process of adding Adverse effects for high dose intravenous administration, also Pharmacodynamics and Pharmacokinetics for high dose intravenous. David notMD (talk) 12:43, 22 December 2023 (UTC)

Added blood pressure subsection based on two meta-analyses. Did not add text and ref (one meta-analysis) about intravenous VitC for burns treatment, as results were deemed inconclusive by authors. David notMD (talk) 12:01, 23 December 2023 (UTC)

Replaced Food fortification. David notMD (talk) 00:44, 4 January 2024 (UTC)

Added Sepsis subsection under Medical. David notMD (talk) 16:32, 5 February 2024 (UTC)

Nominating for FA

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)

Copyvio check 18 January 2024

1. 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.
2. 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
3. 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
4. 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:

1. https://www.ncbi.nlm.nih.gov/books/NBK230149/ now showing up as a 53.1% Violation
2. https://www.nap.edu/read/9810/chapter/7 now showing up as 56.1% Violation
3. http://lpi.oregonstate.edu/mic/vitamins/vitamin-C now showing up as a 39.8% Violation
4. 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)

Ref fixes

A FA reviewer recommended consistency in reference page numbering and sentence versus title case in article titles. Addressing this is resulting in a large number of Edit summaries as ref fix (minor). David notMD (talk) 13:07, 13 February 2024 (UTC)

Completed. David notMD (talk) 14:16, 20 February 2024 (UTC)

FA nomination not accepted

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)

Vitamin C oral absorption

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:

1. "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"
2. "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"
3. "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)

Further research is needed

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)