Vitamin D2 (ergocalciferol) is produced by plants while D3 (cholecalciferol) is made by animals. When produced by animals the body must have exposure to UV rays (sunlight).
Vitamin D promotes the absorption of calcium and phosphorous, which are vital in forming and maintaining strong bones and teeth. The intake of high fiber in the diet reduces absorption. Like other fat soluble vitamins, excessive intake of Vitamin D can possibly lead to toxicity.
Functions of Vitamin D:
• Precursor of active hormone form 1, 25-dihydroxycholecalciferol formed in the kidney
• Plays a central role in the maintenance of bone health
• Essential for calcium absorption; and the regulation of parathyroid hormone (PTH) and calcitonin
• Regulates the excretion of calcium from the kidney and maintains normal calcium blood concentrations
• Vitamin D receptors are found in many other tissues and affects the rate of cell growth and differentiation
• Vitamin D may also be involved in regulating cell growth and maintaining a healthy immune system