Effect of Calcium, Exercise, Estrogen in Preventing Osteoporosis Studied

With the help of a color computer monitor and a machine called a dual photon absorptiometer, Gail Dalsky, an exercise physiologist, can tell women things about themselves they probably never knew, or even thought about.

The machine measures bone density, yielding important information that can determine whether a person is at risk of developing osteoporosis, a potentially disabling disease that primarily strikes women after menopause.

Osteoporosis is caused by the loss of bone density resulting from the sharp decline of estrogen production after menopause, which usually occurs between age 45 and 55. Bones are weakened and become susceptible to fracture.

Dalsky and Dr. Jo-Anne Smith, director of the Osteoporosis Center at the University of Connecticut Medical Center in Farmington, are conducting a study on the effects of calcium, estrogen and exercise on bone density and are looking for evidence that osteoporosis can be prevented. The study is being conducted on women who had their final menstrual period more than three months earlier, but less than five years ago.

“We know that estrogen stops bone loss. And we know that in certain populations, exercise will help to a small extent,” said Dalsky, who has a doctorate in exercise physiology from Brigham Young University in Provo, Utah. “What hasn’t been done, especially in the early post-menopausal woman or in any study, is to use both treatments.”

While it is recommended that women get the recommended amount of calcium in their diet, taking calcium supplements alone will not prevent osteoporosis. When calcium supplements are combined with estrogen supplements, they seem to make the estrogen more effective in strengthening bone, Dalsky said.

An unrelated study of osteoporosis by Yale University researchers shows that women taking the hormone Calcitonin by nasal spray are maintaining bone mass.

The women in the University of Connecticut study will be placed in four groups. One group will receive calcium only, another will receive calcium and will exercise, another will take estrogen and calcium and the fourth will get a combination of calcium, estrogen and exercise, Dalsky said. The researchers hope to have 120 volunteers.

“We hope that by combining exercise with the estrogen, a woman who is low in bone mass upon entry into the study can maintain her bone mass, and that with the combination of exercise and estrogen, we can reduce her risk of fracture by making her bones stronger. That’s the goal,” Dalsky said.

The gradual loss of bone is painless until a fall or bump causes a fracture. Nearly 250,000 hip fractures occur each year that are related to osteoporosis, according to the National Osteoporosis Foundation. These fractures can leave a person permanently disabled.

The disease is also responsible for the “dowager’s hump” that some elderly women have, which is the result of numerous small fractures of the vertebrae. Since bone is lost as a result of the aging process, men can also develop the disease, but for them it does not usually occur until they reach their late 70s or 80s.

Bone density is measured using the dual photon absorptiometer. The patient lies flat on her back while a mechanical arm moves along her body, pausing at certain points. A camera emits a small amount of radiation, the same amount of background radiation that occurs naturally in this area.

A computer printout shows the distinct outline of a hip bone socket known as the proximal femur, and another shows the lower vertebrae that intersect with the pelvis. These areas are of particular interest to the researchers.

“Because of the type of bone that is predominantly in the spine, it is more susceptible to the loss of estrogen,” Dalsky said. “Often we will see decreases in the spine before we see decreases in another body part.”

Even though it is normal to lose some bone mass with age, she said, “in athletes and people who exercise, we’ve found they tend to have a higher bone density at the hip than they do at the spine. In people who don’t exercise, the density in each is about the same.

“For instance, my bone density at the spine is 96-97% (normal), and at the hip it’s about 10% above normal because I exercise,” she said, adding that weight-bearing exercise such as walking, jogging, stair-climbing and weight-training have been shown to have beneficial effects on increasing bone mass.

Dalsky said bones respond to exercise the same way that muscles do. “If a muscle isn’t exercised, it atrophies. If it is exercised, it gets stronger and so does bone. It becomes stronger by adding more mineral to the bone,” Dalsky said.

“Our study is interested in not only keeping good bone in the spine, but also in the hip, because hip fracture is what causes a lot of disability in people. About 50% of people who suffer hip fractures do not resume a normal life. They are wheelchair-bound or unable to live alone, so we are interested in building bone, both at the spine and the hip,” Dalsky said.

There are other factors that are believed to make a person susceptible to osteoporosis, according to the osteoporosis foundation: Women who are thin and small-framed are at greater risk than heavier women. Women who experience early menopause may be more likely to develop osteoporosis than other women. Asian and Caucasian women are more prone to developing the disease than black women, although it is not known why. Calcium deficiency in childhood and early adulthood can also increase the risk. Heredity also plays a role.

Angenette Rienow, 49, a financial secretary who lives in Farmington, Conn., is a volunteer in the University of Connecticut study, which began this past summer.

“I’ve never had any health problems whatsoever, and the little I know about osteoporosis is that slender people are more affected, and I’ve been slender all my life,” she said.

So far, she has had her bone density examined and her cholesterol checked. She has undergone stress tests on a treadmill to determine her level of fitness and kept a diary of her eating habits, and she is taking calcium supplements. In the next few weeks, she will be assigned to a test group.

“I just thought this would be a good opportunity to find out my physical condition, as well as hopefully prevent (disease) from occurring,” Rienow said.

She is not particularly worried about developing the disease, and she has never known anyone who has it. “But I don’t exercise at all. I hear all the things about the importance of exercising, and I am just not self-disciplined enough to do it. I’m hoping that I get in the exercise group because I really want to exercise. I’m a very committed person so if I get in the exercise group, I will be there three or four times a week to exercise.”

Smith said regular exercise for younger women will help keep bones strong, but she stressed that overdoing it can have serious ramifications.

“We’ve all heard about women who exercise so strenuously that their menstrual periods stop for some time. And that’s dangerous because they lose the protection of estrogen and they become susceptible to fracture much earlier in life,” she said.

The study may ultimately show that women who use a moderate exercise program up to and beyond the age of menopause can offset bone loss.

The women in the study will have a program of brisk walking and climbing stairs three times a week in a supervised setting, Smith says. “We have a feeling that will be enough to maintain bone mass, something that is definitely doable for women in that age range,” she said.