Here's how to make the most of your tween's or teen's key bone-building years.

By Sandra Gordon

Bone Health for Kids

Brittni Reum's first broken bone happened in her right heel at age 10. She suffered four more fractures over the next three years in her arms and knee—all from seemingly minor mishaps while playing on the monkey bars or shooting hoops in gym class. "Brittni seemed so fragile that I was afraid to let her go outside or play sports," says her mom, Michele, an accounting manager in Jacksonville, Florida.

Enrolling in a bone-density study at nearby Nemours Children's Clinic revealed that Brittni had osteoporosis. Doctors prescribed calcium supplements and told her to load up on dairy products. Michele hadn't been including much dairy in her daughter's diet since Brittni developed a milk allergy as an infant (most kids outgrow the allergy by age 5). Fortunately, the damage wasn't permanent. Today, at 17, Brittni's bone density is normal, and she hasn't broken any bones in several years.

While her case may sound extreme, Brittni is far from the only teen who needs to be paying attention to bone health. In fact, according to the USDA, 81% of teen girls and 48% of teen boys fail to meet their recommended daily intake of calcium—1,300mg until age 18 and 1,000mg after that. The shortfall comes at a pivotal time because from ages 9 to 18, hormones such as estrogen and insulin-like growth factor 1 kick in, prompting the body to store calcium.

"The teen years are when you acquire nearly half of all the bone you're going to have for the rest of your life," says Susan Coupey, M.D., chief of adolescent medicine at the Children's Hospital at Montefiore in New York City. Your child draws from this "bone bank account" throughout adulthood, especially after age 50, when bone mass naturally starts to decline. If your kid doesn't build bone now, she may not reach her peak bone density. The good news: Research shows that boosting bone density by as little as 5% during the teen years lowers the risk of fractures later in life by 40%. Help your kids maximize their bone-building window of opportunity with our action plan.

Keep Dairy Handy

A recent study reveals that teens ages 14 to 18 typically down 18 ounces of soft drinks daily, which is more than double their milk intake. To help your teen meet his calcium quota, encourage him to have at least four 1-cup servings of dairy a day. Stock up on yogurt, yogurt smoothies, low-fat string cheese, and calcium-fortified cereal bars. Besides providing a healthy dose of calcium and vitamin D, dairy products offer a package of nutrients—including riboflavin, phosphorus, potassium, protein, zinc, and essential amino acids—all of which aid bone development.

If your teen is lactose intolerant, try having her build up her tolerance by consuming small amounts of milk with food, such as a half-cup of milk on cereal, then gradually increasing amounts. According to the American Academy of Pediatrics, teens with lactose intolerance should still drink as much milk as they can tolerate. "Drinking milk fosters good bacteria in the intestine that digests lactose," explains Robert P. Heaney, M.D., professor of medicine at Creighton University, in Omaha. Lactose-free milk is also an option, as are dairy products with low levels of lactose, such as cheddar and Swiss cheeses and yogurt containing active cultures.

Seek Out a Supplement

In addition to calcium, teens also need 200 daily IUs of vitamin D, which helps the body utilize the bone-building mineral. Have your teens, particularly girls, take a daily supplement as extra health insurance, recommends Dr. Coupey. A multivitamin also offers other nutrients teens may be missing, such as folic acid.

Give Team Sports a Go

Bones also need regular weight-bearing exercise, such as walking, running, and jumping, to get stronger. Unfortunately, many teens aren't getting the recommended 60 minutes of daily physical activity their bodies need. But a recent study found that teens who participated in team sports, such as soccer, basketball, ultimate Frisbee, baseball, and rugby, had higher bone mass than those who didn't. Team sports also offer the chance to build bone mass through weight training, a key component of many organized sports programs.

Pay Attention to Her Period

If your daughter hasn't gotten her first period by age 14, or if she misses her period anytime for three to six months in a row, see a doctor. Delayed puberty or missed periods may be the result of excessive dieting and overexercising, and can trigger the fall of estrogen levels, compromising peak bone mass, explains Saralyn Mark, M.D., associate professor of medicine and ob-gyn at Yale University and Georgetown University School of Medicine.

Should Your Teen Get a Bone Test?

The DEXA bone scan isn't used as a screening tool for healthy children under 18. "Healthy teens, even those who've had multiple fractures, don't need a bone mineral density test," says John Mazur, M.D., a pediatric orthopedic surgeon at Nemours Children's Clinic in Jacksonville, Florida. Possible bone density problems in these teens can be detected with just a physical exam or by assessing their diet, he says. But your child may need regular scans if she has an illness or takes medication for an illness that can impact bone density, such as celiac disease, lupus, rheumatoid arthritis, asthma, diabetes, Crohn's disease, epilepsy, cerebral palsy, muscular dystrophy, Cushing's syndrome, kidney disease, leukemia, or cancer.

Copyright © 2008. Used with permission from the April 2007 issue of Family Circle magazine.