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Prolonged nursing and the risk of bone loss.

Women who nurse their infants for six months or more lose a significant amount of the mineral calcium from their bones, according to a new report. Although most women make up for that loss shortly thereafter, researchers speculate that such bone loss may put certain new mothers in jeopardy of potentially crippling fractures later in life.

Lactation, or the production of milk, requires a tremendous amount of calcium to ensure that nursing infants form a strong skeleton. But previous investigators disagreed on whether some of that bone-building mineral comes from maternal bone. So epidemiologist MaryDan R. Sowers at the University of Michigan in Ann Arbor and her colleagues decided to take a closer look at the bones of nursing mothers.

The researchers recruited 98 healthy women during the last months of their pregnancy, They measured bone density two weeks after delivery and again at various points after childbirth.

The team discovered that women who nursed their babies for six months or longer showed an average loss of bone density of 5.1 percent from the lower spine and a loss of 4.8 percent from the top of the leg bone. "That's actually a lot of bone," Sowers says.

Women who bottle-led their infants from birth or breastfed for less than a month showed no such loss, the team reports in the June 23/30 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION.

Sowers says the bone loss was not explained by differences in age, diet, or physical activity. Indeed, she notes, most of the women in the extended lactation group consumed large amounts of dietary or supplemental calcium.

For most healthy women, any bone mass lost during nursing will quickly be recovered. Moms who weaned their babies between six and nine months of age had recovered all of their lost bone a year after the baby's birth. Women who nursed beyond nine months had not yet rebuilt that lost bone.

The average U.S. woman nurses her baby for just three months and thus is unlikely to lose significant amounts of bone. Yet Sowers worries that teenage mothers and women who are malnourished may lose a critical mass of bone during lactation. This might put them at risk of developing osteoporosis - a bone-robbing disorder - after menopause.

"This isn't to say that women shouldn't breastfeed," says Stephen P. Heyse of the National Institute of Arthritis and Musculoskeletal and Skin Diseases in Bethesda, Md. Young women should make sure they get enough calcium to build strong bones before they get pregnant, he adds.
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Title Annotation:mothers who nurse longer than six months lose significant amounts of calcium from their bones
Author:Fackelmann, Kathy A.
Publication:Science News
Article Type:Brief Article
Date:Jun 26, 1993
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