Vitamin D is a fat soluble vitamin that is mainly acquired from the sun. The majority of your vitamin D levels are naturally produced by your body, in the skin during sunlight exposure. Vitamin D plays an important role in the development and maintenance of strong, healthy bones, as it boosts calcium absorption. Vitamin D is also necessary for a healthy immune system.
Vitamin D is naturally found in only a few foods. These include fatty fish such as mackerel, salmon and sardines, fish liver oils and eggs. Other foods may contain vitamin D that has been added during the manufacturing process, such as some fortified milks and infant formulas, orange juice, cereals and breads. Adequate vitamin D intake cannot be obtained via diet alone.
The term ‘vitamin D’ refers to not one, but several different forms of the vitamin. Two forms are important in humans: vitamin D2 (ergocalciferol) and vitamin D3 (colecalciferol). Vitamin D2 is synthesised by plants, whereas vitamin D3 is the form naturally synthesised in your skin through exposure to the sun’s ultraviolet B (UVB) rays. Both Vitamin D2 and Vitamin D3 are biologically inactive forms of Vitamin D. Before they can become active in your body, they must be converted to active forms in the liver and kidneys.
Vitamin D supplements may contain vitamins D2 or D3. Vitamin D2 is derived from fungus or yeast, when exposing foods to ultraviolet light. Vitamin D3 is made in a similar way to how it is naturally produced in the skin of humans and animals. It is usually sourced from lanolin in sheep’s wool. Ostelin uses vitamin D3, the form naturally produced by your body.