The major role of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D helps the body absorb calcium, which forms and maintains strong bones. It is used alone or together with calcium to improve bone health and decrease fractures. Vitamin D may also protect against osteoporosis, high blood pressure, cancer, and other diseases. Table 1 identifies the various forms of Vitamin D and their associated functions within the human body.
Table 1. Forms of Vitamin D and their Function.Forms of Vitamin D | Function within the Body |
D2 (Ergocalciferol) | - Absorption of calcium and phosphorus
|
D3 (Cholecalciferol) | - Helps the body absorb calcium
|
Calcidiol (25-hydroxyvitamin D) | - Not an active form of vitamin D until converted to calcitriol (1,25-dihydroxyvitamin D)
- Converted in the kidneys
|
Calcitriol (1,25-dihydroxyvitamin D) | - Increases the level of calcium (Ca2+) in the blood by increasing the uptake of calcium from the gastrointestinal tract
- Increases reabsorption of calcium by the kidneys
- Increases release of calcium from the bone
|