Calcium and exercise each day may keep osteoporosis at bay, according to a new study conducted at the University of Wales and University of Exeter. Research indicates that prepubescent children should receive 700 mg to 800 mg of calcium (about three 8-ounce glasses of milk) and perform about 25 to 40 minutes of vigorous activity (such as running, playing tag, or jumping rope) every day to grow healthy bones (Journal of Applied Physiology, 2004, vol. 97, no. 4). In the UK study, researchers suggest that because at least 90 percent of peak bone mass is accrued by the end of adolescence, it is important to optimize bone growth in younger years. Other research in the United States emphasizes that exercise is more important than calcium in creating dense and healthy bones (Journal of Pediatrics, 2004, vol. 144, no. 6). The bottom line: Calcium won’t hurt, and exercise always helps.