HERSHEY, Pa.--Exercise has more effect on bone mineral density (BMD) and strength in young women than calcium supplementation, according to researchers at Penn State College of Medicine. The study, published in Junes issue of the Journal of Pediatrics (144, 6, 2004), is part of the larger Penn State Young Womens Health Study, an ongoing observational study began in 1990 of 112 healthy female adolescents representative of Caucasian females attending public schools in Pennsylvania.
Researchers tracked body composition, hip bone measurements and bone strength of 80 women for 10 years. Calcium intake, frequency of exercise and oral contraceptive use was also recorded; the total average calcium intake was between 618 mg/d and 1498 mg/d. They found no significant relationship between average daily calcium intake and total bone gain from ages 12 to 22 in young adult hip bone mineral density; oral contraceptives were also found to have no effect. There was only a small positive relationship between calcium intake and bone variables, but a significant association between sports exercise score and young adult bone mass and strength, said Tom Lloyd, Ph.D., professor of health evaluation sciences at Penn State College of Medicine. Our statistical analysis of sport-exercise in adolescence showed that exercise is responsible for between 16 percent and 22 percent of the variation in hip bone mineral density and bending strength. Lloyd continued, Overall, data from the Penn State Young Womens Health Study indicates that calcium intake greater than 500 mg/d during adolescence does not result in clinically appreciable increased body bone accrual or increased adult bone mass. He added, however, that similar longitudinal studies of other ethnic and racial groups are needed to more fully evaluate the importance of the results for American women.
[U]nderstanding how modifiable lifestyle factors affect bone accrual and development of bone strength is of critical clinical importance. If we know how to optimize bone building and strength in youth, we may be able to develop a preventive strategy to reduce the more than 1.3 million fractures a year, Lloyd said.