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Bone Gains in
New Mothers
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Assistant professor of pediatrics
Judy Hopkinson examines a bone
density scan of a breast-feeding mother.
(K9510-1)
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Osteoporosis causes bones to become
fragile. Bones in the hip, spine, and wrist are especially susceptible and can
break unexpectedly if the disease is not prevented or treated. Fractures of the
hip and spine frequently require hospitalization and surgery and can result in
permanent disability.
In the United States alone, 28 million people—80 percent of them
women—suffer from this debilitating disease. Some studies have suggested
that the loss of bone associated with breast-feeding may increase the risk of
osteoporosis later in life.
Now, researchers at the ARS Children's
Nutrition Research Center in Houston, Texas, led by Judy M. Hopkinson, have
examined the changes that occur in bone mass and density after pregnancy. This
is the first such study to evaluate the long-term process of bone accretion
after pregnancy and lactation.
The researchers also compared the differences in the changes that occur in
breast-feeding and formula-feeding women. "Because of the increased risk
of osteoporosis, the decline in bone density associated with lactation has
received considerable attention," says Hopkinson.
"Some studies have found decreases of 4 to 6 percent in lumbar spine bone
mineral density (BMD) during the first 6 months of lactation." Hopkinson
says these losses are thought to be caused by the low estrogen levels in
breast-feeding women. Lactation delays the onset of menses and the cyclic
release of estrogen for several months. In addition, about 210 milligrams of a
nursing mother's calcium a day are lost in breast milk.
Other studies suggest that while bone loss does occur, bone density normally
returns to baseline levels and that women who do not breast-feed do not
experience net changes in their bone mass or density.
So the researchers were surprised to find that 2 years after pregnancy, both
women who did and did not breast-feed not only regained their baseline levels
of BMD but actually achieved net gains.
While those who breast-fed lost some bone mass and density during early
breast-feeding, short-term breast-feeders (less than 9 months) ended up with
more bone than they had immediately after delivery. Researchers also found that
women who breast-fed for more than 9 months took longer to recover their lost
bone mineral.
In the women who did not breast-feed, more bone was deposited earlier in the
cranial region, which includes the jaw, teeth, and skull.
"These results indicate that lactation delays bone mineral accretion and
temporarily alters its regional distribution in postpartum women," says
Hopkinson.—By Jesús
García, Agricultural Research Service Information Staff.
This research is part of Human Nutrition, an ARS National Program (#107)
described on the World Wide Web at http://www.nps.ars.usda.gov.
Judy M. Hopkinson is with the
USDA-ARS Children's Nutrition Research
Center, Baylor College of Medicine, 1100 Bates St., Houston, TX 77030;
phone (713) 798-7971, fax (713) 798-3692. |
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"Bone Gains in New Mothers" was published
in the July
2001 issue of Agricultural Research magazine.
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Last Modified: 03/11/2005
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