We use superior science to make smarter formulas like Jarrow Formulas® Vitamin D3 1000 IU. It provides cholecalciferol, which is the form produced by the skin in response to UVB exposure (sunlight), and may also improve vitamin D status better than equivalent amounts of ergocalciferol. The body converts vitamin D3 to calcitriol, which enhances dietary calcium and phosphorus absorption, supports production of osteocalcin (an important protein in bone), and supports a healthy immune response.* *These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.