FAYETTEVILLE, Ark. — A University of Arkansas study shows that two percent of college-age women already have osteoporosis. A further 15 percent have sustained significant losses in bone density, and may be well on their way to developing the disease. The study also reveals some surprising risk factors, which may help explain why so many young women have dangerously low bone density-and provide them with the information they need to avoid problems in the future.

"I want women not just to live longer, but to live better," says dietician and health sciences professor Lori Turner. Turner thinks that millions of young women may be putting themselves at risk for developing osteoporosis up to 50 years before symptoms appear. Analyzing the diet and exercise habits of 164 college-age women, she came up with some surprising conclusions about the origins of this complex disease.

Turner collected bone density readings from the hips and spines of women between the ages of 18 and 30, using DEXA (dual energy X-ray absorptiometry) scans to generate complete pictures of her subjects’ skeletons. A computer then analyzed these images, measuring the bone densities of the young women and comparing them to a database collected by the National Center for Health Statistics. Turner then correlated her subjects’ bone densities with a barrage of possible risk factors: exercise, diet, and other lifestyle habits.

After putting her data through statistical analysis, Turner discovered something shocking: two percent of her young subjects already had bone densities low enough to cause osteoporosis of the spine. A further 15 percent had osteopenia-their low bone densities put them at increased risk for developing osteoporosis.

Turner found that Depo-Provera, a common method of birth control that consists of hormone injections every three months, was associated with significant bone loss, especially with long-term use. Depo-Provera is far more convenient than the Pill and just as effective, but many young women aren’t aware of its potential risks. Turner thinks that women who stick with Depo-Provera should be aware of this possible side effect and consider having their bone density levels checked.

Some of Turner’s subjects had extremely low body weights, which they maintained almost exclusively through dieting. Wanting to look thin, they avoided exercise because it would increase their muscle mass. These women were at highest risk for reduced bone density. Their low body weights exerted less pressure on their bones, so their bodies had no reason to maintain bone strength. And they often eliminated dairy products from their diets, thus losing their primary source of calcium. To prevent bone density loss, young women should get about 1000 milligrams of calcium per day by eating foods such as dairy products and calcium-rich vegetables, or by taking calcium supplements.

Young women who had participated in high school athletics had the highest bone densities, a finding that underscores the importance of exercise and physical education during the school years. Weight-bearing exercises-activities like weight training, gardening, jogging, walking, and aerobics-are the best overall way to strengthen bones. Parents and students are often more concerned about academics than athletics. But prioritizing physical activity during the school years not only improves health-it also helps young people form good habits that they are more likely to continue throughout their lives.

Bones reach their peak mass around the age of 30. Estrogen protects bones and stimulates their growth, and the loss of estrogen at menopause causes bone density to decline more sharply. So Turner’s research has important implications for the young women in her study, who still have a few years to improve their bone mass if they need to do so. She compares bone density to saving money and putting it in the bank: "The more you save, the more you will have to draw on later if necessary."

According to the National Institutes of Health, more than 10 million Americans have osteoporosis, 80 percent of them women. The disease threatens a further 18 million. Osteoporosis gradually and almost imperceptibly robs victims of their mineral reserves, causing their bones to become more porous and leading to fractures, deformity, and disability. The disease causes 1.5 million fractures a year, and treatment costs are a staggering $13 billion, more than asthma or breast cancer. Twenty percent of women with osteoporosis-related hip fractures die within a year.

Osteoporosis inflicts more than physical pain; it takes a great toll on women’s emotional health, robbing them of their independence and self-esteem. Victims of osteoporosis often suffer from depression and isolation.

Many people assume that osteoporosis is a natural part of aging. Turner prefers to see it as a frightening but preventable disease. Her findings will help educate the medical community and the public about the importance of prevention-targeting young women who are at risk while they still have time to change their habits and improve their bone health.