Advanced Levels of Vitamin D! For Bone & Colon Health Compare Active Ingredients To Caltrate® 600+D† Guaranteed Quality - Laboratory Tested Calcium is an important mineral for supporting bone health. Calcium also works to support muscle and nerve function. Vitamin D3 is added to assist with Calcium absorption and as support for immune function. Adequate Calcium and Vitamin D3 as part of a healthful diet, along with physical activity, may reduce the risk of osteoporosis in later life.