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Bone savers: rating lifestyle and drugs.

Osteoporosis, an embrittling bone loss common among postmenopausal women, causes roughly 1.3 million fractures in the United States each year. A new Australian study -- the first to pit the three most common preventive regimens head to head -- confirms what other studies have suggested: Estrogen-replacement therapy offers the best protection against osteoporotic bone fractures. However, the same study shows that in the absence of hormone supplements, a combination of regular exercise and calcium-rich diet can significantly slow osteoporosis.

"I was surprised that this lifestyle approach was as successful as it was," says study director Richard L. Prince of the University of Western Australia in Perth.

He and his co-workers recruited 120 nonsmoking women, aged 52 to 60, and assayed their bone density at three fore-arm sites every three months for two years. Densities initially hovered in the lower 40 percent of those seen in women the researchers had studied previously, indicating a high risk of eventual fractures.

The researchers encouraged the women to take at least one hour-long, low-impact aerobics class and two brisk, 30-minute walks a week. In addition, they gave all 120 women identical-looking sets of pills. One-third received daily placebo pills, another third took I gram of calcium per day, and the rest received estrogen and progestins (other hormones in some estrogen-replacement therapies) at a dose taken by many U.S. women today.

The investigators compared these women with 42 others who had average-density bones. Though intended as a control group, those 42 proved nearly as active as the volunteers on the experimental egimens.

In the Oct. 24 NEW ENGLAND JOURNAL OF MEDICINE, Prince and his colleagues report that the women had to undertake the equivalent of two hours of brisk walking daily before they halted bone loss. Because most women did not reach that activity level, the exercise-only and control groups lost about 2.5 percent of their bone density each year. Women who combined calcium and exercise slowed their bone loss to between 0.5 and 1.3 percent annually, depending on the forearm site. Only those receiving the hormone showed a density increase, ranging from 0.8 to 2.7 percent per year.

Though interesting, these results may not reflect similar changes in the loadbearing bones, such as the hip and spine, which are most likely to undergo osteoporotic fractures, cautions Miriam E. Nelson of the Agriculture Department's Human Nutrition Research Center on Aging in Boston.

Still, the Australian investigators think their findings have important implications for public health. Because estrogen-replacement therapy requires medical supervision and may cause side effects, Prince and his co-workers suggest reserving the hormone treatment for women at highest risk -- those with low bone density -- and advising others simply to exercise and take calcium.

But estrogen's cardiovascular benefits, reported in the same journal, may tip the balance in favor of the hormone. Researchers at Harvard Medical School and Brigham and Women's Hospital in Boston have shown for the first time that even low does of estrogen -- 0.625 milligrams per day -- can foster positive bloodcholesterol changes in postmenopausal women. Overtime, they say, the observed decreases in low-density lipoprotein ("bad") cholesterol and increases in high-density lipoprotein ("good") cholesterol might reduce cardiovascular risk in women by more than 40 percent.

The Boston study, which involved 31 women aged 43 to 69, also shows why estrogen offers greater benefits when administered orally rather than through the skin or into the blood: It goes straight to the liver, the central organ in lipoprotein metabolism. "It now appears that women who take [oral] estrogen may produce a little more low-density lipoprotein cholesterol [in the liver] compared with women who don't take estrogen, but that their ability to get cholesterol out of their bloadstream is massively increased," explains Brian W. Walsh, who led the study.
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Title Annotation:prevention of osteoporosis
Author:Raloff, Janet
Publication:Science News
Date:Oct 26, 1991
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