Vitamin D2 supplements

Type of vitamin D found in food and used as a dietary supplement.

- Ergocalciferol

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Vitamin D

Group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects.

Cholecalciferol (D3)
Calcium regulation in the human body. The role of active vitamin D (1,25-dihydroxyvitamin D, calcitriol) is shown in orange.
Global vitamin D serum levels among adults (nmol/L).
The photochemistry of vitamin D biosynthesis in animal and fungi
Thermal isomerization of previtaminD3 to vitamin D3
In the epidermal strata of the skin, vitamin D production is greatest in the stratum basale (colored red in the illustration) and stratum spinosum (colored light brown).
Liver hydroxylation of cholecalciferol to calcifediol
Kidney hydroxylation of calcifediol to calcitriol

In humans, the most important compounds in this group are vitamin D3 (also known as cholecalciferol) and vitamin D2 (ergocalciferol).


Sterol found in cell membranes of fungi and protozoa, serving many of the same functions that cholesterol serves in animal cells.

The gonane skeleton, with the IUPAC recommended numbering of the carbon atoms

In human nutrition, ergosterol is a provitamin form of vitamin D2; exposure to ultraviolet (UV) light causes a chemical reaction that produces vitamin D2.


Edible mushroom native to East Asia, which is now cultivated and consumed around the globe.

Fresh shiitake mushroom in the vegetable market at Hong Kong
Shiitake growing wild in Hokkaido
Korean pyogo-bokkeum (stir-fried shiitake mushroom)
Japanese ekiben {{nihongo||椎茸めし|shiitake-meshi}}
Lentinan, a beta-glucan isolated from the shiitake mushroom
Young shiitake mushrooms on a log

Like all mushrooms, shiitakes produce vitamin D2 upon exposure of their internal ergosterol to ultraviolet B (UVB) rays from sunlight or broadband UVB fluorescent tubes.


Type of vitamin D that is made by the skin when exposed to sunlight; it is found in some foods and can be taken as a dietary supplement.


There are conflicting reports concerning the relative effectiveness of cholecalciferol (D3) versus ergocalciferol (D2), with some studies suggesting less efficacy of D2, and others showing no difference.

Vitamin D deficiency

Defined as a vitamin D level that is below normal.

The normal process of Vitamin D absorption
Normal bone vs. Osteoporosis
Child with rickets
Vitamin D2 supplements

Since vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) are fat-soluble, humans and other animals with a skeleton need to store some fat.


Biologically active organic compound with four rings arranged in a specific molecular configuration.

Structure of 24-ethyl-lanostane, a hypothetical steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC-approved ring lettering and atom numbering.
Gonane, the simplest steroid, consisting only of the common steroid nucleus
Steroid 5α and 5β stereoisomers
Cholecalciferol (vitamin D), an example of a 9,10-secosteroid
Cyclopamine, an example of a complex C-nor-D-homosteroid
Simplification of the end of the steroid synthesis pathway, where the intermediates isopentenyl pyrophosphate (PP or IPP) and dimethylallyl pyrophosphate (DMAPP) form geranyl pyrophosphate (GPP), squalene and lanosterol (the first steroid in the pathway)
Mevalonate pathway
Human steroidogenesis, with the major classes of steroid hormones, individual steroids and enzymatic pathways. Changes in molecular structure from a precursor are highlighted in white.
alt=Chemical diagram|Testosterone, the principal male sex hormone and an anabolic steroid
alt=Chemical diagram|Cholic acid, a bile acid, showing the carboxylic acid and additional hydroxyl groups often present
alt=Chemical diagram|Dexamethasone, a synthetic corticosteroid drug
alt=Chemical diagram|Lanosterol, the biosynthetic precursor to animal steroids. The number of carbons (30) indicates its triterpenoid classification.
alt=Chemical diagram|Progesterone, a steroid hormone involved in the female menstrual cycle, pregnancy, and embryogenesis
alt=Chemical diagram|Medrogestone, a synthetic drug with effects similar to progesterone
alt=Chemical diagram|β-Sitosterol, a plant or phytosterol, with a fully branched hydrocarbon side chain at C-17 and an hydroxyl group at C-3

Vitamin D forms such as ergocalciferol, cholecalciferol, and calcitriol

Agaricus bisporus

Edible basidiomycete mushroom native to grasslands in Europe and North America.

A. bisporus being cultivated
White Agaricus bisporus
Two Agaricus bisporus mushrooms that have fused together
Portobello mushrooms
Cross-section of a portobello cultivar
Ventral view of a portobello cultivar with a bisected stipe
Grilled portobello, feta, and rocket salad on toasted baguette

While fresh A. bisporus only contains 0.2 micrograms (8 IU) of vitamin D as ergocalciferol (vitamin D2), the ergocalciferol content increases substantially after exposure to UV light.


Active form of vitamin D, normally made in the kidney.

Calcitriol synthesis

Compared to other vitamin D compounds in clinical use (cholecalciferol, ergocalciferol), calcitriol has a higher risk of inducing hypercalcemia.


Fleshy, spore-bearing fruiting body of a fungus, typically produced above ground, on soil, or on its food source.

The Eatable Natural mushroom grow in India
The psychotropic mushroom Amanita muscaria, commonly known as "fly agaric"
Amanita muscaria, the most easily recognised "toadstool", is frequently depicted in fairy stories and on greeting cards. It is often associated with gnomes.
Morphological characteristics of the caps of mushrooms
Maitake, a polypore mushroom
A mushroom (probably Russula brevipes) parasitized by Hypomyces lactifluorum resulting in a "lobster mushroom"
Amanita jacksonii buttons emerging from their universal veils
The blue gills of Lactarius indigo, a milk-cap mushroom
Morchella elata asci viewed with phase contrast microscopy
Agaricus bitorquis mushroom emerging through asphalt concrete in summer
Yellow flower pot mushrooms (Leucocoprinus birnbaumii) at various states of development
The Agaricus bisporus, one of the most widely cultivated and popular mushrooms in the world
Culinary mushrooms are available in a wide diversity of shapes and colors at this market stand at the San Francisco Ferry Building.
Young Amanita phalloides "death cap" mushrooms, with a matchbox for size comparison
Psilocybe zapotecorum, a hallucinogenic mushroom
There are over 100 psychoactive mushroom species of genus Psilocybe native to regions all around the world.
Ganoderma lingzhi
A tinder fungus, Fomes fomentarius

The US Department of Agriculture provided evidence that UV-exposed mushrooms contain substantial amounts of vitamin D. When exposed to ultraviolet (UV) light, even after harvesting, ergosterol in mushrooms is converted to vitamin D2, a process now used intentionally to supply fresh vitamin D mushrooms for the functional food grocery market.

Vitamin D-binding protein

Protein that in humans is encoded by the GC gene.

A representation of the 3D structure of the protein myoglobin showing turquoise α-helices. This protein was the first to have its structure solved by X-ray crystallography. Toward the right-center among the coils, a prosthetic group called a heme group (shown in gray) with a bound oxygen molecule (red).

It is able to bind the various forms of vitamin D including ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3), the 25-hydroxylated forms (calcifediol), and the active hormonal product, 1,25-dihydroxyvitamin D (calcitriol).