Calcium supplements may increase risk of heart attacks, and drugs known as bisphosphonates taken to prevent osteoporosis carry significant risks (jaw bone and femoral fractures).
On the other hand high intake of oral vitamin D3 safely protects against osteoporosis with daily intake of 4,000 to 8,000 IU’s or once per week dosage of vitamin D3. This provides well below reported toxic levels. Enough sun exposure to provide this would increase the risk of skin cancer – basal cell and melanoma. Sun screens with an SPF rating above 15 are now recommended for almost everyone, with reapplication every 2 hours while in the sun, which also blocks vitamin D absorption.