Fourteen-year-old Brianna is a tall, slim girl who loves basketball, track, and swimming. When Brianna’s mom brought her in for a sports physical one afternoon, she mentioned that Brianna’s grandmother had recently fallen and broken her hip. “Her doctor said she has osteoporosis,” she said. “I know it runs in families, and I’m worried about Brianna breaking bones, especially as active as she is. She’s probably a little young to have osteoporosis, but is there anything we can do to prevent it?”

I assured Brianna and her mom that it certainly wasn’t too early to be concerned about osteoporosis—in fact, following a few simple steps now could give Brianna her best chance to build healthy bones for life.

This month in “Your Child’s Health,” Duke pediatric rheumatologist Egla Rabinovich, MD, MPH, shares what parents need to know about osteoporosis and children.

--Dennis Clements, MD, PhD

Dr. Rabinovich

When one thinks of bones, what often comes to mind are the hard, dead bones of skeletons. However, bones are living tissues that are always changing, even as you sit reading this! Your body is always creating new bone cells to replace the old ones, a process that is necessary for the bones to stay healthy and perform their three vital functions. First, there is a structural function: bones give support to our body, allow our legs and arms to function, and protect organs such as heart and lungs. Second, the essential elements of blood are made in the center, or marrow, of bones. Third, bones act as a reservoir for essential minerals, most importantly calcium, magnesium, and phosphorus. In fact, 99 percent of the calcium found in the human body is found in bone.

Childhood is a unique time in bone biology—not only is there the constant turnover of cells that occurs in adult bones, but the bones are also growing. For this reason, childhood is our best window of opportunity for preventing osteoporosis.

How do we measure bone strength?

Osteoporosis is a disease of abnormally weak bones that increases the risk of fractures (broken bones). One of the most common tools used to diagnose osteoporosis is a DEXA machine. DEXA stands for “dual energy radiographic absorptiometry,” which is a specialized type of X-ray. As rays are passed over the body, they “see” how much mineral is in the skeleton and also measure the area of the skeleton. The result is called the bone density. While the World Health Organization defines osteoporosis as having “a bone density that is 2.5 standard deviations below that seen in a healthy normal adult,” there is no accepted definition for osteoporosis in children.

As children grow, their bones grow and the corresponding bone density rises continually during each year of growth. During the teenage years the bone density takes a big jump; this rapid increase follows the growth spurt and is under hormonal control. In the late teens and early twenties, our bone density hits a maximum, called the “peak bone mass.” Once peak bone mass is achieved, it never can increase further. Thus, if bone development is adversely affected during childhood, the potential for osteoporosis increases—even though we may not see fractures until 20 to 40 years later! This is why osteoporosis during childhood is often called a “silent” disease: it may be present, but the resulting fractures do not occur until much later in life.

What are risk factors for osteoporosis?

There are plenty of well recognized risk factors for osteoporosis in the elderly: low calcium intake, inadequate vitamin D intake, physical inactivity, race (Caucasians being more at risk than African-Americans), female gender, being very thin, premature menopause, excessive caffeine intake, cigarette smoking, excessive alcohol intake, medications (especially corticosteroids such as prednisone), and family history of osteoporosis.

In children, however, the risk factors are not firmly established. It appears that children who are more physically active have increased bone densities; a greater calcium intake has also been linked to higher bone densities. However, teenage girls who exercise so much that their menstrual periods go away, or who are anorexic, are at risk for osteoporosis. Juvenile rheumatoid arthritis or juvenile diabetes can increase the risk of osteoporosis for young people, as can taking steroids.

Prevention and treatment of osteoporosis

The best medicine for osteoporosis is prevention, and the time to act is during childhood. This is what you can you do for your child to optimize his or her peak bone mass:

• Make sure your child takes enough calcium and vitamin D, and keep your child active. A recent study showed that teenagers in the United States frequently have inadequate calcium intake, and their calcium intake is inversely correlated with soda pop intake—meaning that the more pop they drink, the less calcium they are likely to get! Current recommendations for calcium intake are shown in the accompanying table. For teenagers, this translates into four servings from the milk group daily. Milk is a nice choice for calcium because in the U.S. milk is supplemented with vitamin D, which helps the body utilize calcium.
• Other important sources of calcium include yogurt and cheese, sardines, canned salmon with bones, broccoli, leafy greens, all kinds of meat, and calcium-fortified foods, such as orange juice. Vitamin D is found in supplemented milk, but is also made by the body when skin is exposed to sunlight. Calcium supplements are available by prescription, but are also found in some antacids (for example, Tums and Rolaids). Ask your doctor if your child might benefit from calcium supplementation.
• If you have a strong family history of osteoporosis, or if your child is taking steroids, ask your doctor about the possibility of getting a DEXA scan done. Keep in mind, however, that one of the problems with childhood osteoporosis is that treatments have been geared towards adults. Treatment for osteoporosis in childhood has not been established and should be considered experimental. There is more research needed on bone health in children and prevention or treatment of childhood osteoporosis. Until then, helping your child prevent osteoporosis with the steps outlined above is the best course of action.

Egla Rabinovich, MD, MPH, is co-chief of the division of pediatric rheumatology at Duke.

Dennis Clements, MD, PhD, is the chief of primary care pediatrics at Duke Children's Hospital.