The randomised, double-blind study, funded by the U.S. Department of Defense, looked at 5,201 female U.S. Navy recruits during eight weeks of basic training from 2002 to 2006 at Great Lakes Naval Station near Chicago, Ill.

The women, ages 17 to 35, were divided into two groups with one group receiving daily pill supplements of 2,000 Mg of calcium and 800 IU (international units) of vitamin D, and the other group receiving placebo pills. Calcium supports bone formation and repair, while vitamin D helps the body absorb calcium. During the study, 170 recruits in the placebo group experienced stress fractures, about 25 percent more than in the group taking the calcium/vitamin D supplements. A history of regular exercising decreased the risk of stress fractures, while cigarette smoking increased the risk.

“What really surprised us is that calcium/vitamin D supplements made a significant difference in such a short period of time. Frankly, we were not sure we would see any statistically significant results in only eight weeks,” said principal investigator Joan Lappe, Ph.D., R.N., a professor of nursing and medicine at Creighton University in Omaha, Neb. The study shows that taking calcium/vitamin D supplements can greatly reduce stress fractures in female military recruits, many of whom are suddenly and dramatically increasing their levels of physical, weight-bearing activity.

Lappe noted that the study may also have implications for non-military athletic populations, such as high school track and field athletes, in whom stress fractures are also problematic. “It appears that supplementation with calcium and vitamin D provides a health-promoting, easy and inexpensive intervention that does not interfere with training goals,” she said.; Source: Creighton University