Vitamin D-3, 1000 IU, 200 Tablets, Source NaturalsSource Naturals Vitamin D3, 200 Tablets, 1000 IU, supports the maintenance of healthy calcium and phosphorus levels in the body, which is essential for strong bones. It aids in maintaining muscle strength in older adults and plays a role in promoting a healthy immune response. The product contains Vitamin D3 (Cholecalciferol), the optimal form of Vitamin D, which is the same form that the body produces when exposed to sunlight and is most efficient