Vitamin D

DCalciferol1,25 Dihydroxy vitamin D1,25-dihydroxyvitamin Daffects the immune systemD 2 Vitamin D (Calciferol)vitamin D deficienciesVitamin D milkVitamin-D
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and multiple other biological effects.wikipedia
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Cholecalciferol

vitamin D 3 vitamin D3colecalciferol
In humans, the most important compounds in this group are vitamin D 3 (also known as cholecalciferol) and vitamin D 2 (ergocalciferol).
Cholecalciferol, also known as vitamin D 3 and colecalciferol, is a type of vitamin D which is made by the skin when exposed to sunlight; it is also found in some foods and can be taken as a dietary supplement.

Ergocalciferol

vitamin D 2 D2ergocalciferols
In humans, the most important compounds in this group are vitamin D 3 (also known as cholecalciferol) and vitamin D 2 (ergocalciferol). Cholecalciferol is converted in the liver to calcifediol (25-hydroxycholecalciferol); ergocalciferol is converted to 25-hydroxyergocalciferol.
Ergocalciferol, also known as vitamin D 2 and calciferol, is a type of vitamin D found in food and used as a dietary supplement.

Calcitriol

1,25-Dihydroxycholecalciferol1,25 dihydroxyvitamin D 3 1,25-dihydroxyvitamin D 3
Instead it could be considered a hormone, with activation of the vitamin D pro-hormone resulting in the active form, calcitriol, which then produces effects via a nuclear receptor in multiple locations.
Calcitriol is the active form of vitamin D, normally made in the kidney.

Vitamin

vitaminsfat-soluble vitaminsfat-soluble vitamin
As vitamin D can be synthesized in adequate amounts by most mammals exposed to sufficient sunlight, it is not an essential dietary factor, although not technically a vitamin.
The thirteen vitamins required by human metabolism are: vitamin A (as all-trans-retinol, all-trans-retinyl-esters, as well as all-trans-beta-carotene and other provitamin A carotenoids), vitamin B 1 (thiamine), vitamin B 2 (riboflavin), vitamin B 3 (niacin), vitamin B 5 (pantothenic acid), vitamin B 6 (pyridoxine), vitamin B 7 (biotin), vitamin B 9 (folic acid or folate), vitamin B 12 (cobalamins), vitamin C (ascorbic acid), vitamin D (calciferols), vitamin E (tocopherols and tocotrienols), and vitamin K (quinones).

Rickets

rachitisrachiticantirachitic
Its discovery was due to effort to find the dietary substance lacking in children with rickets (the childhood form of osteomalacia).
This can result from eating a diet without enough vitamin D, dark skin, too little sun exposure, exclusive breastfeeding without vitamin D supplementation, celiac disease, and certain genetic conditions.

Nuclear receptor

nuclear receptorsnuclearmechanism
Instead it could be considered a hormone, with activation of the vitamin D pro-hormone resulting in the active form, calcitriol, which then produces effects via a nuclear receptor in multiple locations.
Ligands that bind to and activate nuclear receptors include lipophilic substances such as endogenous hormones, vitamins A and D, and xenobiotic endocrine disruptors.

Lumisterol

Lumisterol is a compound that is part of the vitamin D family of steroid compounds.

Osteomalacia

rachiticLoosers zonerickets
Its discovery was due to effort to find the dietary substance lacking in children with rickets (the childhood form of osteomalacia).
Osteomalacia is a disease in which softening of the bones caused by impaired bone metabolism primarily due to inadequate levels of available phosphate, calcium, and vitamin D, or because of resorption of calcium.

Steroid

steroidssteroidogenesisbiosynthesis of steroids
Chemically, the various forms of vitamin D are secosteroids, i.e., steroids in which one of the bonds in the steroid rings is broken.
Ergosterol is responsible for the vitamin D content found in mushrooms; ergosterol is chemically converted into provitamin D2 by exposure to ultraviolet light.

Sunlight

sunshinesolar radiationnatural light
The major natural source of the vitamin is synthesis of cholecalciferol in the lower layers of epidermis skin through a chemical reaction that is dependent on sun exposure (specifically UVB radiation).
Sunshine exposure is needed biologically for the creation of Vitamin D in the skin, a vital compound needed to make strong bone and muscle in the body.

22-Dihydroergocalciferol

22-Dihydroergocalciferol is a form of vitamin D, also known as vitamin D 4 .

Vitamin D5

Vitamin D 5 sitocalciferol
Vitamin D 5 is a form of vitamin D.

Calbindin

vitamin D-dependent calcium-binding proteincalbindin D-28Kcalbindin-D28k
The binding of calcitriol to the VDR allows the VDR to act as a transcription factor that modulates the gene expression of transport proteins (such as TRPV6 and calbindin), which are involved in calcium absorption in the intestine.
Calbindin is a vitamin D–responsive gene in many tissues, in particular the chick intestine, where it has a clear function in mediating calcium absorption.

Vitamin D deficiency

hypovitaminosis Dvitamin Ddeficiency of vitamin D
Vitamin D deficiency can result in lower bone mineral density and an increased risk of reduced bone density (osteoporosis) or bone fracture because a lack of vitamin D alters mineral metabolism in the body.
Vitamin D deficiency can also be caused by inadequate nutritional intake of vitamin D, disorders limiting vitamin D absorption, and conditions impairing vitamin D conversion into active metabolites—including certain liver, kidney, and hereditary disorders.

Nutrition facts label

Nutrition Factsnutrition labelingnutritional information
Because it found mounting evidence for a benefit to bone health, though it had not found good evidence of other benefits, the US Food and Drug Administration (FDA) has required manufacturers to declare the amount of vitamin D on nutrition facts labels, as "nutrients of public health significance", since May 2016.
For vitamin C, vitamin D, vitamin E, vitamin K, calcium, phosphorus, magnesium, and manganese, the current highest RDAs are up to 50% higher than the older Daily Values used in labeling, whereas for other nutrients the recommended needs have gone down.

Bone remodeling

bone metabolismremodelingbone turnover
Thus, vitamin D is also critical for bone remodeling through its role as a potent stimulator of bone resorption.
These controls include the action of several hormones, including parathyroid hormone (PTH), vitamin D, growth hormone, steroids, and calcitonin, as well as several bone marrow-derived membrane and soluble cytokines and growth factors (ex.

Multiple sclerosis

MSmultiple sclerosis (MS)disseminated sclerosis
Vitamin D and multiple sclerosis incidence have been linked, but it is not clear what the nature of any causal relationship might be.
Decreased sunlight exposure resulting in decreased vitamin D production has also been put forward as an explanation.

Bone resorption

resorptionresorbedresorption of bone
Thus, vitamin D is also critical for bone remodeling through its role as a potent stimulator of bone resorption. One of the most important roles of vitamin D is to maintain skeletal calcium balance by promoting calcium absorption in the intestines, promoting bone resorption by increasing osteoclast number, maintaining calcium and phosphate levels for bone formation, and allowing proper functioning of parathyroid hormone to maintain serum calcium levels.
Vitamin D increases absorption of calcium and phosphate in the intestinal tract, leading to elevated levels of plasma calcium, and thus lower bone resorption.

Vitamer

formsvitamers
Several forms (vitamers) of vitamin D exist.

Stress fracture

hairline fracturestress fracturesstress reaction
Athletes who are vitamin D deficient are at an increased risk of stress fractures and/or major breaks, particularly those engaging in contact sports.
During exercise that applies more stress to the bones, it may help to increase daily calcium (2,000 mg) and vitamin D (800 IU) intake, depending on the individual.

Calcium

CaCa 2+ calcium ions
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and multiple other biological effects.
Parathyroid hormone and vitamin D promote the formation of bone by allowing and enhancing the deposition of calcium ions there, allowing rapid bone turnover without affecting bone mass or mineral content.

TRPV6

The binding of calcitriol to the VDR allows the VDR to act as a transcription factor that modulates the gene expression of transport proteins (such as TRPV6 and calbindin), which are involved in calcium absorption in the intestine.
Expression of TRPV6 is vitamin D dependent in mice and humans.

Ergosterol

viosterolergosteroids
Vitamin D 2 is produced by ultraviolet irradiation of ergosterol found in many fungi.
This happens naturally to a certain extent, and many mushrooms are irradiated after harvest to increase their vitamin D content.

Dietary Reference Intake

Tolerable upper intake levelRecommended Dietary AllowanceAdequate Intake
The dietary reference intake for vitamin D issued in 2010 by the Institute of Medicine (IoM) (renamed National Academy of Medicine in 2015), superseded previous recommendations which were expressed in terms of Adequate Intake.

Calcifediol

calcidiol25-hydroxyvitamin D25-hydroxycholecalciferol
Cholecalciferol is converted in the liver to calcifediol (25-hydroxycholecalciferol); ergocalciferol is converted to 25-hydroxyergocalciferol.