This is an organic source of calcium from Irish oyster shells, grown in the clear waters of the Atlantic coast of Ireland. IT has been tested for heavy metal to ensure you are getting the purest, most natural calcium on the market. Added VitD3 enhacnes the absorption of calcium and is vital for health and bones. Calcium is a vital mineral for health not just for bones but for a healthy working metabolism. It decreases with age and is especially beneficial for menopause and women's and mens's beauty and functioning as we get older.