June 11, 2004 -- Exercise works better than calcium in building strongbones, a new study shows. It's a new advisory for teen girls: Physical activityis more important than drinking milk for offsetting osteoporosis.
That finding disputes the current message given to women and girls, writeslead researcher Tom Lloyd, PhD, an epidemiologist with the Penn StateUniversity College of Medicine. His paper appears in the current issue of theJournal of Pediatrics.
"Although calcium intake is often cited as the most important factor forhealthy bones, our study suggests that exercise is really the predominantlifestyle determinant of bone strength in young women," Lloyd says in anews release.
The advent of high-tech bone density screening -- dual energy X-rayabsorptiometry (DEXA) -- has given researchers a tool to measure bone densityand indirectly measure bone strength. That has also helped researchersunderstand the importance that various factors like calcium and physicalactivity play in building bone and preventing osteoporosis.
Studies have shown that as much bone is built between ages 13 and 15 as thatwhich is lost to aging and osteoporosis during the last four decades of life.Therefore, it's crucial that a girl works on optimizing the bone-buildingprocess during adolescence as the best protection against osteoporosis, writesLloyd.
To better understand the factors at work, Lloyd studied 80 girls about 12years old when the study began.
For 10 years, he and his colleagues tracked the girls' bone strength throughyearly DEXA scans of hip bones. They also got information on calcium intake,birth control use (which is reported to help build bone), and physical activitythe girls got -- whether it was sports, marching band, dance, aerobics classes,running, walking, or another activity.
- Calcium intake and birth control pill use had no significant affect on bonestrength, Lloyd reports.
- Sports and exercise did make a big difference -- increasing theyoung women's bone mineral density at the hip 3%-5%.
"We have shown that ages 12 to 16 are important years for bone[building] and that adolescent physical activity is positively related to [bonemuscle density] and bone strength of the young adult hip," writesLloyd.
His study has one limitation: It only involved white girls. Other ethnic andracial groups must be studied to provide a more complete picture ofosteoporosis, calcium, and physical activity, he writes.