Talk:Vitamin A

Vitamin A is not Vitamin A1
Vitamin A is term comprimising various alternative forms of vitamin A like vitamin A1 present in the forms of all-trans-retinol, all-trans-retinyl-esters, retinal and various provitamin A-carotenoids, vitamin A2 present in the form of 3,4-didehydroretinol and its esters as well as / dehydroretinal and the postulated vitamin A3,4, which have no human relevance, and the novel postulated form vitamin A5. In general the term vitamin A is simply used but commonly misused for vitamin A1.

Additional reviews

Vitamin A2

- Discovery and biological relevance of 3,4-didehydroretinol (vitamin A2) in small indigenous fish species and its potential as a dietary source for addressing vitamin A deficiency. La Frano MR, Cai Y, Burri BJ, Thilsted SH. Int J Food Sci Nutr. 2018 May;69(3):253-261. doi: 10.1080/09637486.2017.1358358. Epub 2017 Aug 4. Review. PMID:   28776449

- Ling cod and other fish liver oils rich in vitamin A2. MORTON RA, STUBBS AL. Biochem J. 1946;40(5-6):lix. No abstract available. PMID:   20277273

- The identification of dehydroretinol (vitamin A2) in human skin. Vahlquist A. Experientia. 1980 Mar 15;36(3):317-8. PMID:   7371787

- Reproduction and vision in rats maintained on a retinol-free diet containing 3-dehydroretinol (vitamin A2). Howell JM, Thompson JN, Pitt GA. Br J Nutr. 1967;21(2):373-6. No abstract available. PMID:   4952267

- Conversion of carotenoids to 3-dehydroretinol (vitamin A2) in the mouse. Budowski P, Gross J. Nature. 1965 Jun 19;206(990):1254-5. No abstract available. PMID:   5879787

- Biosynthesis of 3-dehydroretinol (vitamin A2) from all-trans-retinol (vitamin A1) in human epidermis. Törmä H, Vahlquist A. J Invest Dermatol. 1985 Dec;85(6):498-500. PMID:   4067325

- Vitamin A in skin and serum--studies of acne vulgaris, atopic dermatitis, ichthyosis vulgaris and lichen planus. Rollman O, Vahlquist A. Br J Dermatol. 1985 Oct;113(4):405-13. PMID:  2933053

-> and many others, which should be added on the vitamin A2 page....which is just linked with dehydroretinal...I have nom idea how to make two pages out of it. -> I can help..but no idea how to do it

Secondly, vitamin A3 and A4, which have no human relevance: - ACS Chem Biol. 2016 Apr 15;11(4):1049-57. doi: 10.1021/acschembio.5b00967. Epub 2016 Feb 2. The Biochemical Basis of Vitamin A3 Production in Arthropod Vision. Babino D1, Golczak M1, Kiser PD1, Wyss A2, Palczewski K1,3, von Lintig J1. PMID: 26811964 PMCID: PMC4841470 DOI: 10.1021/acschembio.5b00967

-> It will not make a big sense to creat a page about these "vitamins" when they are not really relevent and are just mentioned one time.

Vitamin A5, - is described in a patent and as I heard as a publication submitted. I dont know if this is enough to set up a new page. I have no idea how to do it - as a references we just have this review where it s suggested

---> So, now we have to create a strategy how to explain this well in wiki.

As I said, all is well mixed up in the vitamin A page....and alone I can not start because my added work is blocked.

So, guys and experienced wiki´s tell me what "we" can do and how I can help...

Thanks you

Sources revision
A few comments about this edit. 1) The USDA FoodData Central database continues to be updated (October 2021) and expanded, accounting for new values for the same sources used in the table over years. The values change as more samples and similar sources are analyzed, an ongoing USDA process as the US food supply expands. 2) To check and update data, I browsed through 45 pages of the food source rankings from high to lower contents - a tedious process - as there are hundreds of old revised and new sources in the database, so it is impractical to use the database to find individual sources with the updated data. It's more practical to use the links to go to the nutrition table of individual foods, which may be updated or not. 3) The list of high and low vitamin A foods is subjective. Who still uses cod liver oil as a vitamin A source (was common 60+ years ago), or why should we list spirulina as having little vitamin A? Presenting a representative range of commonly consumed foods in high->low content for the general encyclopedia user is something we should briefly discuss here. 4) I placed a [source] notice for the sentence, "Vitamin A content in animal-sourced foods derives from retinol, while in plant-sourced foods, it derives from beta-carotene and beta-cryptoxanthin which are converted to retinol in the body." 5) We should have a clarifying note beside or under the table about the RAE used as the measurement in the header. Vitamin A may be expressed in IU, ug, or RAE, so is readily a confusing presentation for the general user. Zefr (talk) 18:33, 20 December 2021 (UTC)
 * I agree that historic-only and exotic foods do not belong in this table. In all of the sources tables in vitamin articles, the pattern is generally high to low for commonly consumed foods, including those identified in lay literature as good sources (examples: liver, carrots, sweet potatoes...). The current list was recently shorted from ~30 to 13 entries. I would favor enlarging to 24-30 (as three columns) to be able to show that foods, even those consumed in large quantities (bread, pasta, rice, potatoes, corn) are poor sources. The use of US USDA data tables as a definitive source is problematic, especially when one looks 'behind the curtain' to learn that a value in the 2021 version is present because seven samples were analyzed 17 years ago, but there does not appear to be an alternative. David notMD (talk) 20:16, 21 December 2021 (UTC)
 * Divided to separate tables for retinol and beta-carotene. A combined table (replaced) used RAEs, but the real-time conversion of carotenoids to retinol depends on the body's retinol status.David notMD (talk) 11:55, 6 February 2022 (UTC)

Technical discussion in lede
I find the biochemical discussion in the lede paragraph beginning "Retinol is absorbed..." is too technical for general users, WP:NOTTEXTBOOK #8. Zefr (talk) 19:56, 5 February 2022 (UTC)

Some limited editing proposed as a more general description:
 * Dietary retinol is absorbed from the digestive tract via passive diffusion requiring a specific receptor, SCARB1, which is induced when retinol status is low. Storage of retinol is in lipid droplets in the liver. The capacity for long-term storage of retinol means that well-nourished humans can go months on a vitamin A- and β-carotene-deficient diet, while maintaining blood levels in the normal range. Only when the liver stores are nearly depleted will signs and symptoms of deficiency show. Retinol is reversibly converted to retinal then to retinoic acid, which activates hundreds of genes.
 * I agree (even though I penned it). All improvements welcome before the GA review process starts. And during. And after. David notMD (talk) 20:14, 5 February 2022 (UTC)

Unit inconsistency
I found difficilties interpreting the article due to unit inconsistency: sometimes values are given in μg RAE, and sometimes in IU. Would you mind if I put additional number of IU unit in additional to μg RAE everywhere when μg RAE data is given without an IU, so that we have the IU values as a common denominator? Maxim Masiutin (talk) 01:58, 2 May 2024 (UTC)