What's the difference between vitamin D and D3?

What's the difference between vitamin D and D3?

Vitamin D refers to a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and multiple other biological effects. It exists in several forms, with the two most common being vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).

The primary difference between vitamin D and D3 lies in their sources and structures:

Sources:

Vitamin D2 (ergocalciferol) is synthesized by plants, fungi, and some yeasts when exposed to ultraviolet (UV) radiation.

Vitamin D3 (cholecalciferol) is synthesized in the skin of animals, including humans, when exposed to UVB radiation from sunlight, and it's also found in some animal-based foods.

Structure:

Vitamin D2 has a double bond between carbons 22 and 23, whereas vitamin D3 has a double bond between carbons 22 and 23 and a methyl group at carbon 24.

Both vitamin D2 and D3 can be used by the body, but vitamin D3 tends to be more effective at raising blood levels of vitamin D and maintaining those levels for a longer period compared to D2. Because of this, vitamin D3 is more commonly used in supplements. However, both forms can help prevent vitamin D deficiency when taken in adequate amounts.