Hello,A bisphosphonate can help prevent progression of osteoporosis.Potential side effects include:low calciumgastrointestinal irritationbone,muscle, or joint painosteonecrosis of the jawVitamin D3 is better supplement than D2 due to efficiency of creating activated Vit D (25-hydroxyvitamin D) which helps prevent fracture.I see no reason other than convenience and cost why the two could not be tak