Bridget Coila
Have you ever worried about the bone health of a child reluctant or unable to eat dairy products or other calcium rich foods? A few new studies showing that exercise is more important than calcium for growing strong bones may ease your mind.
The first study, in the Journal of Pediatrics, looked at 80 young women from the ages of 12 to 22. Researchers tracked the girls' calcium intake, exercise, sports activities, and bone density and strength over ten years. The girls participated in activities as varied as soccer, marching band, dance, and running and their average calcium intake ranged from 618 mg to 1498 mg a day. The researchers found no correlation between the amount of calium in the diet of an individual girl and her bone gain or hip bone density. Exercise, on the other hand, was found to be responsible for both greater hip bone density and bending strength.
Another study, in Medicine & Science in Sports & Exercise, found that building bone strength is as easy as making sure children get at least 40 minutes of vigorous play each day. Researchers recruited 460 children averaging five years old to wear a device that measured their activity levels for four days. Participants' bone density was measured at three places and compared to their activity levels. Children with the highest levels of intense activities like hopping, running and jumping had the best bone strength. The most vigorously playing boys had nine percent more bone mass and 12% more bone strength, and active girls had seven percent more bone mass and 9% more bone strength than their less-active peers
The optimal amount of activity for childhood bone development appears to be about 40 minutes of high intensity play each day, according to researchers. But this doesn't mean that kids need to be continually on the move. The 40 minute total is cumulative, meaning that active play should add up to 40 minutes. Twenty minutes of recess plus twenty minutes of after-school play can easily provide the necessary amount of activity. Participation in vigorous sports or extracurricular activities is another form of active play that parents can encourage. Anything from basketball to karate classes to gymnastics can provide the necessary levels of activity.
Unfortunately, only about a third of U.S. schools offer physical education classes so the traditional way children accumulate physical activity has disappeared. Now it's up to parents to make sure children get the proper amount of exercise for growing bones.
One of the easiest ways to get your children involved in bone-building play is to get them outside. Some kids are more suited to organized activities and will enjoy getting involved with a local soccer league or taking dance classes. Others will be happier playing with siblings or neighborhood friends, in which case, parents can encourage games that involve running, jumping, and hopping. Providing active props, such as balls, jump ropes, and sporting equipment can help encourage active play.
Locating safe play areas in your neighborhood and encouraging your child to frequent them is another good idea, whether that place is your own backyard, a local playground, or a nearby park with room for kids to run. According to Kathleen Janz, Ed.D., the lead author of a study on vigorous play in young children, "The best way to promote activity is to let kids be kids by allowing them to play and enjoy activities that require jumping, tumbling, and running.
Be careful of activities like swimming and riding bikes, which are healthy for children overall, but don't build bone strength. Be sure not to count them in your child's 40 minute total or rely on them for bone building.
Only high-impact activities provide the necessary "jolt" that young bones need to grow stronger. Non-impact activities can be alternated with activities that do build bones including tennis, volleyball, skateboarding, in-line skating, hockey, hiking, and dancing. So set an example for your children, pick up that sports equipment languishing in the corner, and invite your kids outside for an active game or two. They ‚ and their bones ‚ will appreciate it!
Bridget Coila is a research biologist and freelancde writer specializing in health topics. Her articles have previously appeared in Self, American Fitness, and Spirituality & Health magazine.
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