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Vitamin D is a group of secosteroids. Amounts in IU and μg and given throughout the article, but I only see one case that states which form it refers to (D3). At a guess they're all D3 but this should be explicit. According to
this https://walrus.com/questions/converting-micrograms-mcg-of-calcitriol-to-international-units
one IU of D3 is equivalent to one IU of D2, but it makes no sense to talk about an IU of calcitriol as no amount of it can be said to be equivalent to one IU of D3. The URL above does not look like a citable reference, despite looking very scholarly, so I won't edit the article, but someone more knowledgeable might want to, to say something like "all references to IU are to D3" and something similar for μg if that's true. Housecarl (talk) 00:31, 9 December 2023 (UTC)[reply]
Housecarl - New talk topics go to the bottom of the page, WP:TALK. This section of the article explains thoroughly the relationship between μg and IU for D3 and D2 food or supplement sources, which do not distinguish a possible difference in vitamin D production between the two substrates. Calcitriol is not expressed in the article in units of μg or IU. Zefr (talk) 17:28, 9 December 2023 (UTC)[reply]
My point was "Vitamin D" is a group of things and the quantities given do not identity which of those things they refer to. But now I see the Types section says "Vitamin D without a subscript refers to either D2 or D3, or both, and is known collectively as calciferol.[citation needed]". Housecarl (talk) 21:36, 9 December 2023 (UTC)[reply]
To produce Vitamin D, UVB light is required. To have sufficient light containing UVB, the UV index needs to be 3 or higher (≥45 solar zenith angle at sea level).[1] Vitamin D production is maximal at one-third of the minimal erythemal dose. When UV exposure increases to a minimal erythemal dose, vitamin D synthesis stops.[2] One must be south of latitude 50°N to produce vitamin D around the Winter solstice.[3]
Number of minutes at different UV levels to achieve sufficient monthly needs[4][5]
The table assumes that one is outdoors in sunlight for more than 3 times a week, wearing only swim trunks and a t-shirt or swimsuit, and has not applied sunscreen. Such exposure to the entire skin surface corresponds to receiving between 250–1250 μg of vitamin D (10k to 50k IU) per session[6], or a similar amount as obtained by consuming 125–500 ml of cod liver oil (200μg/100ml[7]).
The "summer level" decreases to "winter level" within 6 to 8 weeks after insufficient sun exposure, without supplementation.[8]
Vitamin D absorption from sunlight differs from absorption from supplements.[9] When absorbing 3 minimum erythema doses (the time it takes for the skin to turn red), with the whole body exposed to UV light:
Within 24 hours, serum vitamin D levels rose from 15 nmol/l to 149 nmol/l.
After 1 week, serum vitamin D fell back to its initial value, while serum 1,25-(OH)2-D reached its peak.
Between 2-3 weeks, serum 25-OH-D concentration reached its highest level, while serum 1,25-(OH)2-D fell back to its initial value.
The study does not mention the time it takes for serum 25-OH-D to return to its initial value.
In another study comparing the difference between 1 MED, 625μg D2 (25k IU) supplement, and 250μg D2 (10k IU) supplement[10][11][12][13], they found that vitamin D from the sun lasts significantly longer than supplements. Vitamin D from supplements returned to baseline levels within 2 days, whereas vitamin D from the sun returned after 7 days. EidenNor (talk) 08:02, 24 April 2024 (UTC)[reply]
^((cite journal |access-date=2024-04-05 |date=2011-08-01 |doi=10.2310/JIM.0b013e318214ea2d |first=Michael F. |issn=1708-8267 |last=Holick |pages=872–880 |periodical=Journal of Investigative Medicine: The Official Publication of the American Federation for Clinical Research |pmc=3738435 |pmid=21415774 |series=6 |title=Vitamin D: a d-lightful solution for health |url=https://pubmed.ncbi.nlm.nih.gov/21415774/ |volume=59}
@EidenNor:, per WP:MEDRS, secondary sources (review articles) and preferably recent reviews (less than five years old) are needed to support medical claims. Unfortunately most of the sources provided above are primary. The following are secondary, but more than ten years old.[1][2][3] Please refer to the banner on this talk page ("Ideal sources for Wikipedia's health content") for a link that will identify such sources. For the subject of vitamin D, there are thousands of such recent review articles. Thank you. Boghog (talk) 05:51, 30 April 2024 (UTC)[reply]
Hi @Boghog, it looks like you care a lot about the vitamin D article, and wants to make it best you can. That is something we both are aiming to do.
I agree secondary sources (review articles) and recent review are preferred. I agree that the sources are old, and agree there is many review articles.
Does the source being old make them bad? no. Does it being primary sources make them wrong? no.
Basted on what i read, the subject is undisputed, and taken for grated, and therefor not not part of review articles, like Vitamin D: The “sunshine” vitamin.
I have been unable to fined a review articles focusing on the timeline of vitamin D absorbing, in the 0-8 weeks from 1-5 MED, in high resolution.
Other that not be WP:MEDRS what is preferred, do you have any other objections? EidenNor (talk) 17:26, 1 May 2024 (UTC)[reply]
References
^Holick MF (March 2004). "Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis". The American Journal of Clinical Nutrition. 79 (3): 362–371. PMID14985208.
^Holick MF (2009). "Vitamin D and Health: Evolution, Biologic Functions, and Recommended Dietary Intakes for Vitamin D.". Clinical Reviews in Bone and Mineral Metabolism. 1 (7): 2–19. doi:10.1007/s12018-009-9026-x.
^Holick MF (August 2011). "Vitamin D: a d-lightful solution for health". Journal of Investigative Medicine. 59 (6): 872–880. PMID21415774.