Talk:Vitamin D

Preparation for nominating for GA

Reviewing all references for compliance with WP:MEDRS, old versus new editions, old and potentially replacable by more recent, duplications, etc. David notMD (talk) 09:11, 21 November 2024 (UTC)

There quite a lot of times the articles fails to WP:MEDSAY. Bon courage (talk) 09:16, 21 November 2024 (UTC)

I agree, and will attempt to address that as part of my review process. David notMD (talk) 09:38, 21 November 2024 (UTC)

The closer I look, the worse it looks (including that there were two bone health sections, now consolidated). David notMD (talk) 03:41, 22 November 2024 (UTC)

Either copying or moving sections to my Sandbox to edit there, and then return to article. Example: History. David notMD (talk) 12:05, 23 November 2024 (UTC)

Moved COVID-19 to Health effects and removed WP:MEDSAY text. Need to check for new lit on government or non-gov organizations issuing statements on D and COVID. David notMD (talk) 14:26, 23 November 2024 (UTC)

Completely rewrote Excess section and moved to after Deficiency. David notMD (talk) 14:16, 27 November 2024 (UTC)

You're doing a great job reviewing this for the GA nomination. Thanks. However do you think the section of Excess should be longer than the one on Deficiency? The magnitudes of these problems is very different. I think the current version has lost the problem of incorrect measurement/contamination as a cause.Jrfw51 (talk) 18:07, 27 November 2024 (UTC)

Jrfw51 I addressed Excess first because I thought the quality was worse that Deficiency, but D definitely needs work!!! I expect Vitamin D deficiency will provide useful content and references. David notMD (talk) 23:38, 27 November 2024 (UTC)

Working on the Evolution section and last paragraph of Lead. The entire Lead will likely need work after all the other content is revised. David notMD (talk) 13:18, 4 December 2024 (UTC)

Added paragraph to History on cod liver oil as treatment for rickets predating identification of vitamin D as the active by 100 years. David notMD (talk) 09:28, 6 December 2024 (UTC)

Addod three images and removed a global map image. David notMD (talk) 03:56, 8 December 2024 (UTC)

Jrfw51 Almost ready to replace the Deficiency section, with some references removed and others added. David notMD (talk) 06:28, 17 December 2024 (UTC)

Replaced Deficiency and Fortification sections David notMD (talk) 19:58, 20 December 2024 (UTC)

Added Infant deficiency subsection. David notMD (talk) 20:27, 28 December 2024 (UTC)

Added Dark skin deficiency subsection. David notMD (talk) 17:23, 30 December 2024 (UTC)

Purging more of the pre-2000 refs and will install newer when those sections are revised.David notMD (talk) 19:43, 1 January 2025 (UTC)

Added Treatment subsection to Deficiency David notMD (talk) 12:05, 2 January 2025 (UTC)

Replaced Sources subsection. David notMD (talk) 13:54, 3 January 2025 (UTC)

Started to revise Biosynthesis. David notMD (talk) 05:24, 12 January 2025 (UTC)

Biology, Biosynthesis, Mechanism of action somewhat overhauled, but Intracellular mechanisms stll needs work. David notMD (talk) 08:34, 20 January 2025 (UTC)

Nomination timing

The GA guidelines recommend that an article content be relatively stable before the nomination. For this reason, after I have completed what I see as the changes needed prior to the nomination, I intend to wait several months to see if there are major reverts, revisions or additions by other editors. May request a peer review before the GA nomination. David notMD (talk) 20:13, 22 December 2024 (UTC)

Nominated 9 February 2025. David notMD (talk) 14:27, 9 February 2025 (UTC)

Value of the Biology section?

The Biology section has four refs unique to it (one for the figure). Does the section - with the figure - add significant benefit to the article, or can it be removed, with any useful content and refs moved to other sections? Is the figure itself useful? David notMD (talk) 16:08, 13 January 2025 (UTC)

The lede is well-organized and introduces the biology section in a way that impresses as concise and educational for the common user about how vitamin D is formed and works. Could the biology and biosynthesis sections (and its figures) be combined with the calcium figure (yes, useful) to better introduce the physiological roles for vitamin D early in the article? Zefr (talk) 16:57, 13 January 2025 (UTC)

I will consider that before submitting to GA. The major part I still intend to revise/re-reference is Mechanism of action (and somewhere cover pharmacokinetics). All contributions welcome. David notMD (talk) 19:28, 13 January 2025 (UTC)

A puzzle

For several diseases and health conditions, there are observations of vitamin D deficiency being more prevalent than in healthy populations. For a few, there is additional evidence that supplementation at the amounts tested did not improve the diseases. Is low D a risk factor for these diseases and conditions, or is it something as simple that having these diseases or conditions cause people to have less exposure to UVB from sunlight? Clearly for age, and likely for obesity, these conditions can lead to less skin sun exposure. Without supplements or food fortification, sun exposure is much more of a contributor than diet. David notMD (talk) 18:29, 17 January 2025 (UTC)

For 20+ years, Holick has made the case of increased disease risk due to vitamin D deficiency. A 2019 update here and one from 2023 (unfortunately in an MDPI journal, likely predatory). But is there a WP:MEDASSESS review or clinical guideline to support it? Zefr (talk) 23:19, 17 January 2025 (UTC)

There are literally thousands of nuclear receptors for vitamin D, and therefore thousands of genes either being turned on or off. All this makes vitamin D the Swiss Army Knife of vitamins. Clearly, calcium metabolism is directly affected in ways that have clinical consequences, and I am of the opinion that any involvement of immune and autoimmune conditions is also probably directly related to vitamin D actions. The question remains in my mind as to whether non-calcium, non-immune disease observations are linked to vitamin D deficiency due to direct action, or do these myriad disease states have the indirect commonality of causing less exposure to sunlight, i.e., Occam's Razor. The true test would be whether vitamin D supplementation reverses the diseases. David notMD (talk) 14:37, 18 January 2025 (UTC)

Slight clarification. There is one and only one vitamin D receptor, but this single receptor binds to thousands of response elements, and hence regulates the expression of thousands of genes. Here are two WP:MEDASSESS sources that support that vitamin D deficiency results in increased disease risk:

• Demay MB, Pittas AG, Bikle DD, Diab DL, Kiely ME, Lazaretti-Castro M, Lips P, Mitchell DM, Murad MH, Powers S, Rao SD, Scragg R, Tayek JA, Valent AM, Walsh JM, McCartney CR (July 2024). "Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline". The Journal of Clinical Endocrinology and Metabolism. 109 (8): 1907–1947. doi:10.1210/clinem/dgae290. PMID 38828931.
• Sizar O, Khare S, Goyal A, Givler A (July 2023). "Vitamin D Deficiency.". StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing.

Boghog (talk) 20:25, 19 January 2025 (UTC)

Although a preventive effect for vitamin D on rickets is established, the Endocrine Society guideline states that the "certainty of evidence" for prevention is low-moderate for a) preeclampsia, b) intra-uterine mortality, c) preterm birth, d) small-for-gestational-age birth, and e) neonatal mortality. Other potential effects or associations with lower disease risk remain uncertain due to the evidence that "a causal link between serum 25(OH)D concentrations and many disorders has not been clearly established." The guideline doesn't specify a dose-effect relationship that would justify using this source to say anything about prevention in the article.

The StatPearls short review doesn't give any up-to-date evidence of causality between vitamin D supplementation and disease prevention. All references under Pertinent studies are out-of-date, WP:MEDDATE.

Both reviews state that monitoring vitamin D levels in the general population is not justified, except in high-risk people. Further stated in the Endocrine Society report: "the optimal vitamin D intake and the role of testing for 25(OH)D for disease prevention remain uncertain."

This would suggest we are a long way from using vitamin D to prevent most diseases. Zefr (talk) 21:13, 19 January 2025 (UTC)

Straw man argument. No one is claiming that vitamin D prevents most diseases. That is an absurd assertion. However, there are strong associations between low vitamin D levels and certain diseases. Additionally, vitamin D plays a well-established role in regulating gene expression related to calcium uptake, metabolism, as well as the cardiovascular and immune systems. A plausible mechanism helps demonstrate that the observed association is not coincidental. Moreover, when vitamin D levels are low, supplementation is generally recommended to maintain overall health. Boghog (talk) 07:11, 20 January 2025 (UTC)

Once I am done revising section by section I intend to pause for several months before nominating for Good Article review. During that time I ask all interested editors to amend the article for completeness, gaps, contradictions, neutral point of view, references, etc. I then intend to look at everything with refreshed eyes and proceed. David notMD (talk) 08:28, 20 January 2025 (UTC)

Vitamin D and COVID-19

All of the refs need to be checked. Some are no longer active, or perhaps newer versions have been published. David notMD (talk) 14:52, 18 January 2025 (UTC)

Update completed. Most recent (2024) meta-analyses of supplement trials (large dose oral on hospital admission) concluded significant reductions in ICU admissions and mortality. David notMD (talk) 13:16, 19 January 2025 (UTC)

Nominated for Good Article

Nominating for Good Article. Everyone welcome to review/improve the article while waiting for and during review. David notMD (talk) 14:26, 9 February 2025 (UTC)

Looking at Vitamin C as a model, this article could benefit from an animal synthesis section/subsection within Evolution. It appears that most but not all amphibians, reptiles, birds and mammals have the capacity for skin synthesis, but not dogs, cats, others (?). For example, nocturnal but not diurnal fruit-consuming bats have very low serum D but maintain plasma calcium and bone mineralization. PMID 20804612 has been incorporated into the History section, as it describes lion cubs in London zoo in 1889 being vitamin D deficient and dying from a diet fed to their nursing mothers and the weaned cubs of lean horse meat, treated by changing to goat - including bones - supplemented with cod liver oil, the latter based on observations that CLO treated rickets in human children. David notMD (talk) 15:04, 9 February 2025 (UTC)

Here is an article that describes dermal synthesis of vitamin D in the North Island brown kiwi (Apteryx mantelli), tuatara (Sphenodon punctatus), and New Zealand sea lion (Phocarctos hookeri), and another article describing it in some insects. Reconrabbit 16:10, 10 February 2025 (UTC)

In my Sandbox I am drafting a subsection to cover in general amphibians, reptiles, birds, mammals and fish, plus a few exceptions that do not skin-synthesize (dogs, cats, horses, other?). I doubt that there is merit in this being species-exhaustive (!!!!), but I will look at those links. I do not intend to delve into non-vertebrates, but other editors may choose to go there. David notMD (talk) 17:09, 10 February 2025 (UTC)

Subsection added. David notMD (talk) 04:51, 11 February 2025 (UTC)

GA review (Szmenderowiecki)

This review is transcluded from Talk:Vitamin D/GA1. The edit link for this section can be used to add comments to the review.

Nominator: David notMD (talk · contribs) 14:24, 9 February 2025 (UTC)

Reviewer: Szmenderowiecki (talk · contribs) 13:19, 7 April 2025 (UTC)

Hello there, I am going to spend the next couple of hours reviewing this article. Because this is the first time I am reviewing a topic under MEDRS, I will welcome others' input into the review. I will also refer the article for a second opinion so that the second reviewer catches stuff that I may have missed. I also think a double review is appropriate because this is a vital article and may directly concern the health of readers, who will for the large part take what's written on Wikipedia for granted.

Pinging all editors who have substantially contributed to the article or who have edited the talk page within the last 6 months : Reconrabbit, Boghog, Zefr, Bon courage

I need to take a day or two of break due to family reasons, I will finish the review in due time. Szmenderowiecki (talk) 09:50, 13 April 2025 (UTC)

Overall progress

GA review – see WP:WIAGA for criteria

1. Is it well written?

   A. The prose is clear and concise, and the spelling and grammar are correct:

   There are occasional incomprehensible passages, but otherwise the prose is generally clear and concise.

   B. It complies with the manual of style guidelines for lead sections, layout, words to watch, fiction, and list incorporation:

   I'm not particularly keen on the layout and the order in which this article is written. I have expressed my preference while I was reviewing the article. It is in the order of the subsections of this review.

2. Is it verifiable with no original research, as shown by a source spot-check?

   A. It contains a list of all references (sources of information), presented in accordance with the layout style guideline:

   Easy pass

   B. Reliable sources are cited inline. All content that could reasonably be challenged, except for plot summaries and that which summarizes cited content elsewhere in the article, must be cited no later than the end of the paragraph (or line if the content is not in prose):

   There are several passages that are cited to wrong sources or sources that are presumably outside the article. Many sources in MEDRS contexts are pretty old and should be updated. A few sources are dead. One source is in my opinion misrepresented. There is also the question of using a company that sells cod oil to write about the history of the product.

   C. It contains no original research:

   No problems with this one.

   D. It contains no copyright violations nor plagiarism:

   There is one case I detected that is a copyvio.

3. Is it broad in its coverage?

   A. It addresses the main aspects of the topic:

   The article is pretty detailed, which for me is what matters the most. The medical section is particularly strong IMHO.

   B. It stays focused on the topic without going into unnecessary detail (see summary style):

   There is a minor issue with overemphasis on COVID, but other than that the article is fine.

4. Is it neutral?

   It represents viewpoints fairly and without editorial bias, giving due weight to each:

   The literature review, while incomplete, is representative of the major positions taken by governments and conclusions reached in systematic reviews.

5. Is it stable?

   It does not change significantly from day to day because of an ongoing edit war or content dispute:

   Easy

6. Is it illustrated, if possible, by images?

   A. Images are tagged with their copyright status, and valid non-free use rationales are provided for non-free content:

   B. Images are relevant to the topic, and have suitable captions:

   Per MoS guidance on images, include alternative text for all images in the article. Also, keep images to one side whenever possible to avoid a sandwiching effect. Looks nasty on mobile.

7. Overall:

   Pass or Fail:

   David notMD There is promise in this article. With a bit of work, this can truly be a good article. Szmenderowiecki (talk) 21:56, 13 April 2025 (UTC)

Lead

• Unlike the other twelve vitamins, vitamin D is only conditionally essential - in a preindustrial society people had adequate exposure to sunlight and the vitamin was a hormone, as the primary natural source of vitamin D was the synthesis of cholecalciferol in the lower layers of the skin's epidermis, triggered by a photochemical reaction with ultraviolet B (UVB) radiation from sunlight. - IDK where to start. I'd put a source near conditionally essential. What changed since the beginning of the Industrial Revolution? Did people change so much that vitamin D stopped being a hormone? I don't think I see it anywhere and the lead doesn't say anything about it. I think you can just say how it's generated - sunlight and all that, and that because we can generate some vitamin D from UV radiation, vitamin D is not strictly essential.
• Foods such as the flesh of fatty fish are good natural sources of vitamin D; there are few other foods where it naturally appears in significant amounts - Flesh of fatty fish is among the few significant natural food sources of vitamin D
• are fortified -> add wikilink to Food fortification

Generally

• There's this book called Feldman and Pike’s Vitamin D, which appears to be a comprehensive reference on all things Vitamin D. The fifth edition from 2024 is available on the internet, but the Wikipedia Library does not carry it. I'd strongly advise you check this out.
• There's so much chaos in this article. The order of things I'd expect from a good article is this: what this is, varieties of this thing, how we make it, what it does, how it does what it does, how much of it we need, what happens if there is too much/too little of it, efforts to prevent these problems, if any; other regulations surrounding it, like "allowed health claims", and how it was discovered. Compare with e.g. Nicotinamide adenine dinucleotide (an FA), where the order is roughly the same.

Types

• Vitamin D3 was shown to result from the ultraviolet irradiation of 7-dehydrocholesterol. -> Who showed it? When? There is no source to that effect.

Biosynthesis

• Move up biosynthesis to this section.
• You describe D3 synthesis. Is there any info on D2 synthesis? Are there organisms that can synthetise one but not the other? What's the effect of such change? Maybe there are some organisms that can synthetise both but they are not bioequivalent in these species?

Evolution

• For at least 1.2 billion years, eukaryotes - a classification of life forms that includes single-cell species, fungi, plants, and animals, but not bacteria - have been able to synthesize 7-dehydrocholesterol. When this molecule is exposed to UVB light from the sun it absorbs the energy in the process of being converted to vitamin D. The function was to prevent DNA damage, the converted molecule being an end product without vitamin function. - this doesn't appear to be substantiated by an inline source. If it is hidden in the 2000 source, let me know, but as far as I can see from its abstract, it's not there. The other two cited sources do not confirm this passage. In general, I'd simply put citations at the end of each sentence so that we avoid the appearance of improper editorial synthesis or just sloppy citation practices.
• Ditto some species of not exactly an encyclopedic style of writing
• Only circa 500 million years ago, when animals began to leave the oceans for land, did the UV-converted molecule take on a hormone function as a promoter of calcium regulation. - this is contradicted by the 2022 source cited, which says this: Since the levels of 1,25(OH)2D3 in lamprey are similar to that in higher vertebrates, respective enzymes, such as CYP2R1 and CYP27B1, must have co-evolved with VDR [22]. Similar co-evolution also happened for the vitamin D transport protein vitamin D binding protein (encoded by the GC gene) [25]. This indicates that some 150 million years before the first species left the ocean and had the need for a stable skeleton, vitamin D endocrinology was already established. Thus, from an evolutionary perspective, the control of calcium homeostasis was rather a secondary than a primary goal for establishing the vitamin D endocrine system. The article does say that animals left the ocean, but that was 385Mya, not 500Mya.
• See Evolutionary Biology: Mysteries of Vitamin D in Fish in this book
• Wikilink amphibians, osteoclast
• The second paragraph of evolution is a copyvio from the abstract of this paper, with word-for-word copying of the last sentence which doesn't make much grammatical sense; I have no idea why the other two papers are cited here.

Animal biosynthesis and food sources

• Carnivores and omnivores also get the vitamins from their diets, and herbivores can get some vitamins from fungi that are consumed along with plant foods. I'd like you to expand a bit on this source; however, the source cited to this sentence does not even contain the word "fungi", "mushrooms" or similar.
• In captivity, artificial lighting that provides UVB light is preferred to fortified food -> the only passage that somewhat approaches what is said here is this Dietary sources of vitamin D may not be sufficient to prevent rickets and osteomalacia. Diets with as much as 3,000 IU vitamin D3/kg did not prevent bone fractures and cortical thinning in green iguanas. Bulbs emitting UVB placed over the lizards at ~12–18 in. for 12 hours/day appeared to reverse the signs in the least severely affected lizards. That's not a recommendation. I can't read it from there. The same applies to the following sentence. I can't see this recommendation in birds, which basically says "give supplements or a UV-B source" or in amphibians, where point 6 of the cited paper just says that it's hard to breed amphibians in captivity, which could be due to vitamin D deficiency.
• Unlike land-based vertebrates, large amounts of vitamin D3 are stored in the liver -> Unlike land-based vertebrates, fish store large amounts of vitamin D3...}}
• How much of vitamin D is being produced annually? In which forms is it normally produced?

Biology

• This section appears to be duplicating the Mechanism of action section. I'd like to understand why. Maybe move up the mechanism of action section to this place.

Mechanism of action

• Calcitriol exerts its effects primarily by binding -> Calcitriol, the biologically active form of vitamin D, exerts...
• In the absence of calcitriol, the VDR is mainly located in the cytoplasm of cells. - No source for this statement, ref 207 does not say this. While I know that everything is either inside the nucleus or in the cytoplasm, it could be for example that it is attached to some sort of organelle while it is inactivated (not how it works, but you need to write for the layman who doesn't have a background in biochemistry or cell biology.
• active vitamin D - no full stop after D
• These include TNFSF11 (RANKL), crucial for bone metabolism; SPP1 (Osteopontin), which is important for bone metabolism - weird formulation in this sentence

Metabolism

• The regulation section should be generally incorporated into this section. It may be that you should rename it, but the whole point is, this replies to the "what does it do" and "how does it do what it does" part. You could even put it before the mechanism of action section, as it is now.
• Ref 206 could be updated to the version from 2024. Check if it still says the same thing; maybe add some info that could be new.
• This hydroxylation also leads to a greater degree of inactivation: the activity of calcitriol decreases to 60% of original after 24-hydroxylation, whereas ercalcitriol undergoes a 10-fold decrease in activity on conversion to ercalcitetrol. - source?

Regulation

• Give page in ref 220
• Ref 221 is already getting pretty old; ref 223 is REALLY old.

Dietary intake

• Refs 56 and 57 (NHS and Health Canada guidelines, respectively) are dead/have been moved somewhere else.
• Older recommendations were lower. It is true for the US, but you can't extrapolate from one country only. To make such a statement, you'd need a source analysing several major countries and saying that generally, recommended intake norms are higher today.
• Example text -> move to an efn and attach it to the IU notation.
• A table of the old and new adult daily values is provided at Reference Daily Intake. - no old/new table as far as I can see
• Why is the Canadian and Australian section so short?
• The EU has updated the directive [1]; but the reference values have not changed.
• On the other hand, the EU Commission defined nutrition labelling for foodstuffs as regards recommended daily allowances (RDA) for vitamin D to 5 μg/day (200 IU) as 100% However, for purposes of nutrition labelling, a European Union directive defined the daily reference intake for vitamin D at 5 μg/day.
• You may consider incorporating a few more national guidelines, such as those for Poland, DOI 10.1159/000337547 for Germany (equivalent English-language source), for Italy
• as the IOM - as the US Institute of Medicine
• In certain countries, breakfast cereals, dairy milk and plant milk products are fortified - I'd remove this sentence as you explore the concept of fortification in greater detail

MEDRS

These are the most sensitive areas in terms of MEDRS, so I will be looking into Health Effects, Deficiency and Excess chapters really closely.

• General remark, particularly for the Health Effects part up to Cancer - the sources here are rather old - the typical review cycle is about 5 years and we are sometimes speaking of 15-year-old articles, and even one case from 1989. Any newer systematic reviews covering the same info (unless these ones are considered definitive, as in much higher citation count than newer ones, or current health guidelines)? This isn't a niche topic, so there should be something new. Maybe this will not change the content but we will at least be able to demonstrate that these sources are up-to-date. So please check whether the sources are old, if so, go find newer sources, and edit the article info if there is any difference.
• However, a random check of about 1/3 of sources gives few indications that something is misinterpreted, cited incorrectly or uncited.
• In general, I'm not convinced about the merits of fragmenting the sections in so much detail. A lot of the sections are just one sentence long. Not strictly prohibited but several consecutive subsections of that size don't look pretty.

Health effects

• I don't like the wording of the passage describing the debate over US IoM guideline. It sounds a bit like he said, she said. We could just state something along the lines of: Some researchers advocated for higher recommended blood levels and claimed that the US IOM report's results had calculations with mathematical flaws and were based on poor-quality data. The IoM stood by its conclusions and rejected the criticism.
• Evidence for and against each disease state is provided in detail. I understand why you want to say this, but I'm not a fan of this approach. For starters, fourteen years is a lot in the world of medicine, even if the guideline is still the one used in America. You should use up-to-date summary studies as much as you can, and there should be a lot of them. Secondly, you already have all these subsections for mental illness, bone health, cancer and so on, so I think you should simply cite the info in these sections if you choose to cover it that way, and add that source in the general discussion.
• alfacalcidol - why is there no discussion of that substance as a vitamin D analog? That is definitely relevant to the article, and since we mention the substance (should be wikilinked) in the context of vitamin D, might just as well tell people how it's related.
• Other forms (vitamin D2, alfacalcidol, and calcitriol) do not appear to have any beneficial effects concerning the risk of death - does the Cochrane review - find a new one - describe how, despite the bioequivalency of vitamers, there are different health effects?

• The section about rickets should make it clear that the most common cause of the disease is vitamin D deficiency, like, the first thing you read. It doesn't make it clear, and the one sentence that tries to is with a citation needed tag. You can do it in the deficiency section, but as far as I glanced I'd advocate merging the deficiency/excess sections into the influence on respective organ systems.
• In ref 2, change the archived page to the one that is after the update in July 2024, because now the archived page date is before the publication date, which is a little weird.
• Ref 104 needs to be updated to the current version in 2023
• but either there is no evidence that supplementation has a benefit or not, or for some, evidence indicating there are no benefits - I don't understand what "or not" does here.
• Why is COVID-19 in its separate section if you already have an "infectious diseases" section? Also, the section clearly shows it was written in the heyday of the pandemic, as you can see so much advice that clearly was in response to those who advocated vitamin D to cure COVID. Shorten it in the style of the other sections.
• [homeostatic model assessment-insulin resistance (HOMA-IR)], hemoglobin A1C (HbA1C), and fasting blood glucose (FBG) - remove that, Ctrl+C+V from the abstract of this paper.
• In prospective studies, high versus low levels of vitamin D were respectively associated with a significant decrease in risk of type 2 diabetes, combined type 2 diabetes and prediabetes, and prediabetes. - I don't understand what this is supposed to mean, as there are 2 variables attributed "respectively" to three indicators, and there's just one study to support this.
• A systematic review included one clinical trial that showed vitamin D supplementation together with insulin maintained levels of fasting C-peptide after 12 months better than insulin alone - one trial ain't enough. We need summaries of several trials.
• The clinical trial literature does not yet contain sufficient evidence that supplementation reverses these dysfunctions or improves other aspects of vaginal or urogenital health. I think that's a bad rephrasing of While the findings are not consistently conclusive, they suggest that vitamin D supplementation, whether topically or orally, may offer benefits in improving vaginal symptoms and sexual function and potentially reducing the risk of UTIs. There is some evidence it may help as far as they describe. They also report on two meta-analyses that found no relation, but that's a different story which you don't tell here.

Allowed health claims

• This link has all EFSA-approved health claims for vitamin D supplementation. There are some related to bone growth, so you should add them. Note that a lot of search results are unfortunately irrelevant as they concern other vitamins.
• Ref 164 (Health Canada) and 165 (Japan) are outdated. We need to show the current regulatory framework.

Deficiency

• Ref 17 is outdated for population stats with vitamin D deficiency. Any new info? Ref 18 is borderline.
• According to the US Institute of Medicine Dietary Reference Intake Committee, below 30 nmol/L -> blood concentration below 30 nmol/L...
• Refs 29-32 are rather old.
• Fractional contributions are roughly 20% diet and 80% sunlight - I don't see this in the source, maybe it's in refs 59-60 in the source but the source doesn't say it. Besides, this depends on the kind of diet, so where fatty fish is abundant, there is a lot of supply of vitamin D through the diet.
• with lacto-ovo-vegetarians falling in between due to the vitamin content of egg yolks and fortified dairy products The section about Vitamin D makes no such claim at all - it doesn't even contain a word about eggs or milk products. Read up the source.
• antiretrovirals, anti-seizure drugs, glucocorticoids, systemic antifungals such as ketoconazole, cholestyramine, and rifampicin - wikilink antiretrovirals, glucocorticoids, ketoconazole, cholestyramine, rifampicin
• bolus doses - wikilink bolus
• ...as breast milk is not a meaningful source of vitamin D." - delete this parenthesis. It's enough that the US IoM and (cite some other health authorities) find breast milk an inadequate source of vitamin D.

Excess

• Ultraviolet light alone - sunlight or tanning beds - can raise serum 25(OH)D concentration to a bit higher than 100 nmol/L, but not to a level that causes hypervitaminosis D, the reasons being that there is a limiting amount of the precursor 7-dehydrocholesterol synthesized in the skin and a negative feedback in the kidney wherein the presence of calcitriol induces diversion to metabolically inactive 24,25-hydroxyvitamin D rather than metabolically active calcitriol (1,25-hydroxyvitamin D) - not in the source, so citation needed. Tanning beds don't seem to be discussed - I didn't see it at least - and the biochemical regulatory pathways are just vaguely hinted at there. You can take sourcing from Mechanism of action for the pathway part.
• Are there more reviews discussing harmful levels of vitamin D? I mean, not just the US IoM paper. Only then can we say with certainty that experts do not agree about the threshold toxicity.
• causes abnormally hypercalcaemia abnormal
• Ref 65 redirects to the Merck manual article about vitamin D deficiency, and you want to talk about excess, right?
• Refs 66 and 67 should preferably be updated; 69-71 must be updated as they are too old.
• 7–12 months: 38 μg/d (1500 IU/d); 1–3 years: 63 μg/d (2500 IU/d) - why are μg rounded? We can say 37.5 and 62.5 easily.

History

• I don't think source 225 is reliable per WP guidelines on reliable sources - it's a description of a product that a company sells - and there could be various reasons for writing this story, and a lot of them would be to drive sales up instead of ensuring accuracy. But this may be a starting ground to look for unequivocally reliable sources about cod oil. It doesn't have to be from medical journals, as historical information is not biomedical.
• Source 226 is excellent. It writes about historical sources for first usage of cod oil to treat diseases. Use it.