The strength of your bones depends on their size and density; bone density depends in part on the amount of calcium, phosphorus and other minerals bones contain. When your bones contain fewer minerals than normal, they're less strong and eventually lose their internal supporting structure.
The process of bone remodeling. Scientists have yet to learn all the reasons why this occurs, but the process involves how bone is made. Bone is continuously changing — new bone is made and old bone is broken down — a process called remodeling, or bone turnover.
A full cycle of bone remodeling takes about two to three months. When you're young, your body makes new bone faster than it breaks down old bone, and your bone mass increases. You reach your peak bone mass in your mid-30s. After that, bone remodeling continues, but you lose slightly more than you gain. At menopause, when estrogen levels drop, bone loss in women increases dramatically. Although many factors contribute to bone loss, the leading cause in women is decreased estrogen production during menopause.
Your risk of developing osteoporosis depends on how much bone mass you attained between ages 25 and 35 (peak bone mass) and how rapidly you lose it later. The higher your peak bone mass, the more bone you have "in the bank" and the less likely you are to develop osteoporosis as you age. Not getting enough vitamin D and calcium in your diet may lead to a lower peak bone mass and accelerated bone loss later.
What keeps bones healthy. Three factors that you can influence are essential for keeping your bones healthy throughout your life :
· Regular exercise
· Adequate amounts of calcium
· Adequate amounts of vitamin D, which is essential for absorbing calcium
Sources mayoclinic.com