Osteoporosis is often called a "silent" disease because bone loss occurs without symptoms. Breaking a bone may be the first clue of osteoporosis. Some people learn that they have osteoporosis after they lose height, due to one or more broken bones in the spine, which may occur without any noticeable pain.

The word "osteoporosis" means "porous bone." It is a disease in which low bone mass and the breakdown of bone tissue lead to bone fragility. In the past, both the disease and the fractures that occur from the disease were considered an inevitable part of old age. According to Michigan State University Extension, there are many influences on bone mass and strength, such as genetics, hormones, physical exercise and diet (especially intake of calcium, phosphate, vitamin D and other nutrients).

Your bones are living, growing tissue. Bones are made up of living cells that remove and replace weakened sections of bone. Throughout your life, you constantly lose old bone while you make new bone. Even after children and teens stop growing taller, they continue to produce more bone than they lose. Teens bones get denser until they reach peak bone mass, or the greatest amount of bone, which usually happens between the ages of 18 and 25. The more bone you have at the time of peak bone mass, the less likely you are to break a bone or get osteoporosis later in life.

Around age 30, bone mass stops increasing and begins to decrease. In most women, the rate of bone loss rapidly increases for several years after menopause, then slows down again, but continues afterward. In fact, in the five to seven years after menopause, women can lose up to 20 percent or more of their bone density. In men, the bone loss occurs more slowly. But by age 65 or 70, most men and women are losing bone at the same rate.

According to the National Osteoporosis Foundation, 44 million Americans have low bone density or osteoporosis. In fact, about one in two women and up to one in four men over the age of 50 will break a bone due to osteoporosis. By 2020, half of all Americans over age 50 are expected to have low bone density or osteoporosis.

Low bone mass that is not low enough to be osteoporosis is sometimes called osteopenia. Not everyone who has low bone mass gets osteoporosis. But everyone with low bone mass is at higher risk for getting it. If you have low bone mass, there are things you can do to help slow down bone loss. This could include getting enough calcium and vitamin D, avoiding smoking, limiting alcohol and caffeine and engaging in weight-bearing exercise such as walking. Taking care of your bones is important at any age, and it is never too late to take action. In Osteoporosis: Prevention and treatment –Part 2 you will learn more about what you can do.