Osteoporosis is a bone disease best described as "porous bones." Bones are living tissue, constantly being rebuilt. With osteoporosis, the rate of bone loss is greater than that of bone rebuilding, causing thin, porous bones that break easily.

More than 28 million Americans have osteoporosis or are at high risk of developing it. One in every 2 women and 1 in every 8 men will suffer osteoporosis-related fractures some time in their life. The national cost of osteoporosis and associated fractures is estimated at $10 billion and rising. Osteoporosis causes pain, disability, and loss of independence. However, it is treatable and the amount of bone loss can be prevented.

Your bones develop in stages. From birth through adolescence, new bone is built faster than old bone is removed, so bones grow larger and denser. During adolescence, bones grow stronger at an even faster pace than before. Bone mass peaks between ages 20 and 25, then bone loss can outpace formation. After menopause in women, bone loss accelerates because of a decline in estrogen, a hormone that helps protect bones.

The risk for osteoporosis increases if too little bone is formed during youth, or too much is lost later in life, or both. Size and quality of bone may be genetically determined, but other factors also influence bone health. A family history of osteoporosis or bone fractures, a lifelong low-calcium diet, Caucasian or Asian heritage, lack of exercise, low body weight relative to your height, smoking, drinking excess alcohol, lack of menstruation, and taking certain medications are all risk factors for osteoporosis.

While you can't control all your risk factors, you can make lifestyle choices that will decrease your risk for developing osteoporosis. These include: eating a balanced diet rich in calcium, regularly doing weight-bearing activities, avoiding excessive alcohol, and not smoking. Building healthy bones at any age helps prevent osteoporosis later in life.