Teens and bone strength

What factor is most important to ensure adequate bone density in teenage girls? When 80 young women were followed from age 12 to 22, the only factor in their lives that influenced bone density was exercise. Calcium intake and oral contraceptive use had no effect on bone strength. There may be other factors such as vitamin D levels from sun exposure and dietary sources, but the data pertaining to exercise was so dramatic that the study results are very convincing. How should this study impact our thinking about the minimum daily intake of calcium for children? It should reassure those parents who limit dairy intake because of an allergy or sensitivity to milk, and it should make us less militant about the daily dose of calcium. It should also encourage parents to require an exercise program during early childhood and the teenage years. 

Sports (other than swimming) and dance are excellent forms of weight bearing exercise that will build bone mass. Girls tend to curtail exercise during the teen years, and this study should redouble our efforts to keep teenage girls exercising. If they do not want to continue in the forms of exercise they enjoyed as younger girls, then it is time for them to begin a regular exercise program of running, weight training, and core strengthening that they can maintain throughout their adult lives. Boys who give up their sports teams, skateboards, and bikes should similarly be encouraged to establish an exercise regimen that will maintain their endurance and muscle strength. In this era of academic pressures and tight schedules we need to make time for teens to get moving and stay fit.

This study proves once again that exercise is an essential ingredient for child health. Obesity has become the greatest risk factor for health problems in a majority of Americans (and Canadians!). Children are increasingly at risk of obesity and therefore more likely to develop the serious complications of obesity - diabetes, heart disease, and cancer. A program of proper nutrition and regular exercise is essential to maintaining a high level of health, mental acuity, and emotional well-bing in teenagers. At this crucial time when a transition to lifetime habits is being established, parents need to set an example and require that teens follow that example of eating a quality diet and getting regular exercise. 

Lloyd, T, et al. Lifestyle factors and the development of bone mass and bone strength in young women. Journal of Pediatrics 2004 (June) 144; 6: 776-782