Why should someone supplement with vitamin D Many clinical trials have demonstrated the benefits of vitamin D to support bone strength and density: Supplementation with vitamin D at dosages of 700-800 IU daily or higher has been associated with a 23-26% improvement in bone health, especially for older adults. Why use Vitamin D3 1000 IU It is convenient: Vitamin D3 provides an easy way to increase intake of cholecalciferol - the same form of vitamin D our bodies create naturally. To support healthy bones: Healthy bones need vitamin D to properly use calcium and phosphorus. Vitamin D helps regulate calcium and phosphorus absorption through the intestines, reduces kidney excretion of calcium, and regulates the amount of calcium in the bones. To support a healthy immune system and other health functions in the body: Vitamin D has been shown to enhance healthy cell replication and division, as well as influencing healthy glucose metabolism.