This powerful, one-a-day bone and immune system health formula blends a high-strength 1000IU of Vitamin D3 (the active form of Vitamin D) with important bone-supporting antioxidants. Our bodies need Vitamin D to absorb and use Calcium properly, which helps to maintain healthy bones and reduces the risk of osteoporosis. Boron and Selenium are essential antioxidants that further support bone health, strength and density.