Danger of Chain Reaction : Exercise and Bone Loss

The stubborn pursuit of a lean, trim body may prematurely result in a painful, disfigured mass of osteoporotic bones, warns the American Society for Bone and Mineral Research (ASBMR).

Premature bone loss in a young woman most commonly occurs in those who exercise excessively and eliminate dairy products from their diets, according to ASBMR member Dr. Frederick Singer.

This bone loss, called osteoporosis, makes bones weak, brittle and susceptible to fracture, particularly in the wrist, spine and hip.

"While daily weight-bearing exercise, such as walking or jogging, is beneficial to the prevention of osteoporosis, too much exercise can start a chain reaction which may cause bone loss," Singer said.

"As a woman loses body fat--due to over-exercising--her estrogen production decreases. Estrogen appears necessary for maximum absorption of calcium, the major component of bones. Therefore, the lower the estrogen production, the less calcium may be absorbed."

Excessive exercise, coupled with a poor diet, can lead to such reduced estrogen production that menstruation stops, resulting in infertility and more endangered bone health.

The problem is further complicated by inadequate calcium intake, he says.

"Dairy foods provide about 75% of the calcium in the American diet. Many women eliminate dairy foods from their diet in an effort to save calories not knowing the devastating effect it can have on their health later in life," he said. "In fact, an eight-ounce glass of low-fat milk contains only 121 calories, and nonfat has 86 calories."

Other calcium sources include salmon with bones, sardines, tofu, broccoli and spinach.

"Calcium supplements are available, but we just don't know the long term consequences of taking dietary supplements," Singer said. "We do know, however, that a well-rounded diet will provide adequate calcium along with the other nutrients needed for maximum absorption of the calcium.

A well-rounded diet, according to Singer, includes three dairy group servings a day, such as low-fat milk, yogurt and cheese; two meat group servings; and four daily servings from both the vegetables and fruits and breads and cereals groups.

One dairy group serving equals eight ounce of milk, 1 1/2 slices of cheese or an eight-ounce carton of yogurt.

"By following this pattern, you can be sure you're getting all the calcium you need for healthy bones and long term good health in general," he said.

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