WEDNESDAY, May 7 (HealthDay News) -- Want your teenage daughter to have strong bones? Steer her to soccer or other impact sports, experts suggest, and you may help her prevent low bone density later in life.

Sports such as soccer -- with the combination of weight-bearing exercise and repetitive, "impact-loading" from jumping and running -- have been shown to build bone mineral density in adolescent girls better than some other activities.

Building bone density during the teen years is considered crucial for healthy bone development, helping to ward off osteoporosis, the disease that causes bones to become brittle and break later on in life. Peak bone mass is typically achieved by age 30, according to the National Osteoporosis Foundation.

"It's those years of adolescence, and early teens to late 20s, that are most important" for bone building," said James W. Bellew, an associate professor of physical therapy at Louisiana State University Health Science Center-Shreveport.

Bellew and his colleagues compared the effects of soccer, weight-lifting and swimming on the bone mineral density of teen and pre-teen girls, ages 10 to 17. The groups included 29 swimmers, 16 soccer players and 19 weightlifters.

Soccer players had the best bone density, followed by the weight-lifters and then the swimmers. Bellew's team compared the groups' average bone mineral density to what is considered the norm for a 25-year-old woman.

Soccer players' bone density was significantly greater than the norm, and the weight-lifting group was equal to the norm. The swimmers were lower than the norm. Still, that's not cause for alarm, he said, because the girls were still in their teens and have time to accrue bone density.

Soccer and other "impact" sports expose the body to repeated impact, and that activity is thought helpful to bone health. "Basketball and volleyball may very well do the same" as soccer in building bone, he said. Jogging and tennis may also be good, he added.

The study results, published in the journal Pediatric Physical Therapy, don't surprise Susan Randall, senior director of education at the National Osteoporosis Foundation. "Swimming is not a weight-bearing exercise," she said. "Soccer increases the loading on the bone which actually stimulates bone production."

Bellew isn't discouraging those who love swimming to give up the sport. "The odds are the swimmers' density [in the study] will be fine, because they are active, but our data suggest they aren't accruing as much bone as those who do weight-bearing exercise."

"If your primary objective is to increase bone mass, swimming is not the best," he said. "But in terms of weight maintenance, it's good."

Besides exercise, Bellew suggests teens can boost their bone health by reducing their soda intake and increasing their milk consumption. "Genetics is probably the largest factor," he added, so those with a family history of osteoporosis may want to pay even more attention to bone-building exercise.

Randall agreed that families should pay even closer attention to their children if a parent or grandparent suffers from low bone density. And parents can emphasize a healthy diet for their sons as well as daughters. While men are less likely than women to suffer osteoporosis, they still need to build bone, she said.

One of the first foods teen girls often abandon are dairy products, Randall said, because they perceive them as fattening. Parents should be sure their children get the recommended 1,300 milligrams of calcium a day. That's roughly the amount of calcium in four glasses of milk. And the milk can be low-fat, she said.

More information

To learn more about bone health, visit the National Osteoporosis Foundation.

SOURCES: Susan Randall, R.N., C.F.N.P., senior director of education, National Osteoporosis Foundation, Washington, D.C.; James W. Bellew, P.T., Ed.D., associate professor of physical therapy, Louisiana State University Health Science Center-Shreveport; Pediatric Physical Therapy

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