The optimal blood level of vitamin D3 is 70-80 ng/mL in the 25(OH)D3 form.
Vitamin D3’s Effect on Bones:
Bone formation and maintenance is influenced by 1,25-dihydroxyvitamin D3 (1,25D3). Supplemental vitamin D3 (cholecalciferol), such as that found in our product D3ZO, is converted into 1,25D3 in a two step process: first the cholecalciferol is taken to the liver to be hydroxylated into 25(OH)D3, and then it is taken to the kidneys to be hydroxylated a second time into 1,25D3.
1,25D3 is intimately involved in bone remodeling, the process by which your body breaks down old bone tissue and replaces it with new tissue so that your bones stay healthy and strong as you age. One way in which 1,25D3 regulates bone remodeling is by binding to the vitamin D receptor (VDR) of osteoblasts and osteoclasts. The VDR is a protein within cells that 1,25D3 must bind to before its biological effects are exhibited. Osteoblasts are cells that are primarily involved in the formation of new bone, while osteoclasts are involved in the breaking down of old bone. When 1,25D3 binds to the VDRs of osteoblasts, several important processes are initiated: there is increased calcium and phosphate absorption from the intestines to be used in bone formation; it facilitates the synthesis and secretion of collagen and other proteins by osteoblasts to be used in bone formation; the synthesis of parathyroid hormone is inhibited which prevents the breakdown of bone. When 1,25D3 binds to the VDRs of osteoclasts, excessive bone resorption (the breaking down of bone) is prevented.
In addition to preventing excessive resorption of bone by binding to the VDRs of osteoclasts, it has also been shown that 1,25D3 prevents the over-mineralization of bone. Over-mineralization of bone is when osteoblasts deposit too many minerals into newly forming bone, causing it to be abnormally dense. 1,25D3 prevents the over-mineralization of bone by inducing the expression of genes that inhibit mineralization (BGLAP and SPP1) and inhibiting the expression of a gene that stimulates mineralization (IBSP).
These are only some of the mechanisms by which 1,25D3 helps maintain bone health. There are likely dozens if not hundreds of additional ways that 1,25D3 plays a role in bone formation and reparation. It can therefore be concluded that optimal bone health simply cannot be achieved without sufficient levels of vitamin D3.