There are 206 bones that make up the skeletal body. Bone is a living tissue that is constantly being removed and replaced. Bones need normal sex hormones, calcium, vitamin D, proteins and weight bearing / strengthening exercise to keep them healthy. Peak bone mass is reached at 25-30 years old. After the mid-forties bone density is lost approximately 0.5-1% a year. As we get older and over 50, more bone is naturally lost than is replaced. This causes bones to become fragile and therefore, they can break easily.