Vitamin D for normal bone

Vitamin D comes from two sources in humans; it could either be synthesized in form of vitamin D3 (cholecalciferol) under the influence of solar UV-B radiation in the epidermis, or be absorbed from the diet or from supplements and food additives, which in some countries may contain vitamin D2 (ergocalciferol).

This vitamin is necessary for normal tooth and bone formation. Vitamin D contributes to bone health by regulating calcium absorption. Vitamin D is crucial for maximizing gut absorption of calcium via vitamin D dependent Ca receptors. It is estimated that adequate vitamin D status increases Ca absorption to 30–40% of intake compared with only 10–15% absorption without adequate vitamin D.

Adequate vitamin D is necessary for absorption of calcium. Vitamin D is made in the skin after exposure to sunlight. Estimates include 5-16 minutes of sun exposure 3 times a week on the face, hands, and arms will meet vitamin D needs.

The recommended adequate intake (AI) of vitamin D for children and adults up to 50 years is 200 IU, whereas the recommended AI for adults 51–70 years and 71+ years is 400 IU and 600 IU, respectively.
Vitamin D for normal bone