FRIDAY, Nov. 9, 2008 (HealthDay News) -- Calcium and vitamin D supplements may do more than strengthen bones in older women. These vital nutrients may also help younger, active women reduce their risk of stress fractures.
To illustrate that point, many bone health experts refer to a recent study of more than 5,200 female U.S. Navy recruits that found that women who didn't take additional calcium and vitamin D were about 25 percent more likely to suffer a stress fracture than women who took the vitamin and mineral combination.
"The most common time for a stress fracture is when you're increasing your exercise levels -- when you're going from doing nothing to doing a whole lot. It's too much, too fast, and the bone can't handle it," explained Dr. Sabrina Strickland, an orthopedic surgeon who specializes in sports medicine at the Hospital for Special Surgery in New York City.
"Before you embark on any sort of exercise regimen, take calcium and vitamin D supplements to reduce your chances of a stress fracture," she advised.
Stress fractures occur when muscles become tired and can't absorb shock properly. That force is then transferred to the bone instead. After time, that added shock can cause a tiny crack in the bone. More than half of all stress fractures occur in the lower leg, according to the American Academy of Orthopaedic Surgeons.
Women are more likely to suffer stress fractures, particularly women involved in just one particular sport, such as running, tennis, gymnastics or basketball.
"Stress fractures are seen in people who do the same activity over and over again," said Dr. Elton Strauss, an associate professor of orthopedic surgery at the Mount Sinai Medical School in New York City.
In the Navy recruit study, the women were undergoing eight weeks of basic training. All were between the ages of 17 and 35. The women were randomly divided into two groups. One group was given daily supplements containing 2,000 milligrams of calcium and 800 international units of vitamin D, while the other group took a placebo.
More than 300 women developed a stress fracture. About 170 women who took a placebo experienced a stress fracture. That means about 25 percent more of the placebo group had a stress fracture compared to those taking the supplements.
Results of the study were presented at a recent meeting of the Orthopaedic Research Society.
"I recommend that all of my female patients take 1,200 to 1,500 milligrams of calcium citrate and 800 international units of vitamin D3 daily," said Strickland.
Strickland also advised that athletes should cross-train to avoid stress fractures. If you're a runner, she suggests lifting weights. "Don't just participate in impact activities," she cautioned.
Strauss agreed that cross-training is crucial for strengthening muscles and ligaments, which will help prevent stress fractures. "You shouldn't do the same sport seven days a week," he said.
Strauss also suggested making sure you get plenty of sleep. And, if you're participating in a lot of exercise, you should "push for at least 12 to 15 grams of protein at each meal." Protein is important for the metabolism of muscles and bones, he said.
Strauss also recommended getting adequate levels of calcium, because it's "good for the entire musculoskeletal system." He said he thought most runners and other athletes spend enough time outdoors that they might not need a vitamin D supplement, because the body makes vitamin D when exposed to sunlight. However, athletes who are vigilant about applying sunscreen may need the additional vitamin D.
Finally, when you begin a new activity, take it slow, Strickland advised. "Don't do too much too fast. The typical rule for runners, and one almost nobody follows, is to increase the amount of running by 10 percent each week," she said.
To learn more about stress fractures, visit the American Academy of Orthopaedic Surgeons.