Cholecalciferol is one of the five forms of vitamin D. [36] Cholecalciferol is a secosteroid, that is, a steroid molecule with one ring open. [37] Mechanism of action [ edit ] Authorities disagree about how much vitamin D the body needs. In the United States, the Daily Value (DV) for vitamin D has been set at 800 International Units (IU). Vitamin D is one of the body’s most important vitamins, helping it with a variety of tasks: Vitamin D contributes to the normal function of the immune system and is very important for the body’s structural system, maintaining normal bone and muscle function. Vitamin D3 also contributes to the normal absorption and utilisation of calcium and phosphorus. Lotfi-Dizaji L, et al. Effect of Vitamin D Supplementation Along With Weight Loss Diet on Meta-Inflammation and Fat Mass in Obese Subjects With Vitamin D Deficiency: A Double-Blind Placebo-Controlled Randomized Clinical Trial. Clin Endocrinol (Oxf) . 2019 ;90(1):94-101.

The VDR regulates cell proliferation and differentiation. Vitamin D also affects the immune system, and VDRs are expressed in several white blood cells, including monocytes and activated T and B cells. [21] In vitro, vitamin D increases expression of the tyrosine hydroxylase gene in adrenal medullary cells, and affects the synthesis of neurotrophic factors, nitric oxide synthase, and glutathione. [22] Photochemistry [ edit ] The photochemistry of vitamin D biosynthesis in animal and fungi Thermal isomerization of previtamin D 3 to vitamin D 3Another surprising thing about vitamin D3? It’s not actually a vitamin, but a pro-hormone. It’s considered a pro-hormone because the body is able to produce it on its own by absorbing sunlight on the skin. Yang K, Kurihara N, Fan K, Newmark H, Rigas B, Bancroft L, etal. (October 2008). "Dietary induction of colonic tumors in a mouse model of sporadic colon cancer". Cancer Research. 68 (19): 7803–10. doi: 10.1158/0008-5472.CAN-08-1209. PMID 18829535. If you are using the liquid form of this medication, carefully measure the dose using a special measuring device/spoon. Do not use a household spoon because you may not get the correct dose.

Fischer J, Ganellin CR (2006). Analogue-based Drug Discovery. John Wiley & Sons. p.451. ISBN 978-3-527-60749-5. Archived from the original on 30 December 2016 . Retrieved 29 December 2016. Chen C, Zhai H, Cheng J, Weng P, Chen Y, Li Q, etal. (August 2019). "Causal Link Between Vitamin D and Total Testosterone in Men: A Mendelian Randomization Analysis". The Journal of Clinical Endocrinology and Metabolism. 104 (8): 3148–3156. doi: 10.1210/jc.2018-01874. PMID 30896763. S2CID 84841517. The conversion from ergosterol to vitamin D 2 follows a similar procedure, forming previtamin D 2 by photolysis, which isomerizes to vitamin D 2 ( ergocalciferol). [172] The transformation of previtamin D 2 to vitamin D 2 in methanol has a rate comparable to that of Too much Vitamin D can lead to Hypervitaminosis D (Vitamin D toxicity). This rarely occurs except people who mega dose on Vitamin D. Vitamin D is fat soluble—so you can consume too much. In 2016 in the United States, the Food and Drug Administration (FDA) amended food additive regulations for milk fortification, [138] stating that vitamin D 3 levels not exceed 42 IU vitamin D per 100 g (400 IU per US quart) of dairy milk, 84 IU of vitamin D 2 per 100 g (800 IU per quart) of plant milks, and 89 IU per 100 g (800 IU per quart) in plant-based yogurts or in soy beverage products. [139] [140] [141] Plant milks are defined as beverages made from soy, almond, rice, among other plant sources intended as alternatives to dairy milk. [142]Doctors often favor the supplement because of the dangers of UV rays and the difficulty of getting vitamin D from diet alone. Oily fish is the best source of D3, but few people want to eat fish daily. Gorham ED, Garland CF, Garland FC, Grant WB, Mohr SB, Lipkin M, etal. (March 2007). "Optimal vitamin D status for colorectal cancer prevention: a quantitative meta analysis". American Journal of Preventive Medicine (Meta-Analysis). 32 (3): 210–6. doi: 10.1016/j.amepre.2006.11.004. PMID 17296473.