context: Did you know there are different types of osteoporosis? While white women are at the greatest risk, the disease does not discriminate. Men and women of all ethnic groups can develop osteoporosis. So can children and teenagers. Women experience more rapid bone loss in their 50s than men do. By the time they're both in their late 60s, though, men and women lose bone mass at the same rate. Statistics show that 2 million men have osteoporosis today. Another 12 million are at risk. And one out of every four men over age 50 will break a bone due to osteoporosis. A woman's risk of osteoporosis rises sharply after menopause. This is especially true for white women and Asian women. It's also especially true for women who have small, thin frames. Teens and college-age women who are thin and who exercise excessively are at a high risk of not having menstrual periods. This is a condition called amenorrhea. Loss of menstrual periods is linked to decreased estrogen levels. Decreased levels of estrogen may cause osteoporosis. A diet low in calcium and other bone-boosting nutrients can also contribute to low bone density. Teenage girls who restrict their eating and who lack menstrual periods are at risk of osteoporosis and fractures. Young female athletes who try to reach a low body weight for running or dancing are more likely to not have periods. So are those who compete in scoring sports such as gymnastics and figure skating. A young female athlete who appears to be in top physical condition often has the highest risk of low bone density -- osteoporosis -- and fracture, especially if she has an eating disorder and lacks periods. In fact, a fracture may be the sign that first alerts the doctor there is a problem. Up to 30% of ballet dancers suffer from repeated stress fractures, which can be a sign of eating disorders and low body weight. There are two kinds of osteoporosis in children: secondary and idiopathic. Secondary juvenile osteoporosis refers to osteoporosis that develops as a result of another condition. This is by far the most common kind of osteoporosis in children. Some of the diseases that can lead to osteoporosis in children include: anorexia nervosa Cushing's syndrome cystic fibrosis diabetes homocystinuria, a genetic metabolic disorder hyperparathyroidism hyperthyroidism juvenile arthritis kidney disease leukemia malabsorption syndrome osteogenesis imperfecta, sometimes called brittle bone disease Some osteoporosis in children is a direct result of disease itself. With rheumatoid arthritis, for example, children may have lower than expected bone mass, especially near arthritic joints. Certain drugs can also lead to juvenile osteoporosis. These can include chemotherapy for cancer, anticonvulsants for seizures, or steroids for arthritis. If your child has one of these conditions, ask your child's health care provider about testing and monitoring bone density. Idiopathic juvenile osteoporosis means that there is no known cause of the disease. This type of juvenile osteoporosis is rare. It develops most often just before the onset of puberty. Although most of the bone density may return during puberty, children with juvenile osteoporosis usually have lower peak bone mass as adults. No matter what the cause, juvenile osteoporosis is a very serious condition. You build about 90% of your bone mass by the time you're ages 18 to 20. Losing bone mass during prime bone-building years can put a child at serious risk for long-term complications such as fractures. Here are some things you can do to build bone now and help prevent osteoporosis later: Do weight-bearing exercise. Just like your muscles, your bones need to be worked regularly to stay strong. Studies show that young women who participate in athletics have the highest bone density. They also show that postmenopausal women who take part in regular exercise can prevent or reverse bone loss by almost 1% a year. Eat a diet rich in calcium and vitamin D. Adults (men and women) under age 50 need 1,000 mg (milligrams) of calcium each day. All women over age 50 should get 1,200 mg of calcium daily. Men ages 51 to 70 should get 1,000 mg of calcium a day and 1,200 mg after they reach age 70. Men and women under age 70 need 600 international units ( IU) of vitamin D daily. That increases to 800 IU of vitamin D after age 70. Experts feel that it is best to get your calcium and vitamin D from your diet. Good natural sources of these nutrients include milk, yogurt, cheese, dark green leafy vegetables, and fortified cereals and juices. Three and a half ounces of cooked salmon contains 90% of your daily dose of Vitamin D. If you can't get enough calcium and Vitamin D in your diet, talk to your health care provider. Don't smoke. The more you smoke and the longer you smoke, the greater risk you have of fracture in old age. Quitting smoking appears to lower this risk over time. If you are concerned about your bone health, talk to your health care provider. Screening tests are available to check your bone health.