Bone Gains in
August 8, 2001
Childbearing and nursing do not appear
to permanently diminish the density of new mothers bones, according to a
recent study by scientists at the Childrens Nutrition Research
Center at Baylor College of
Medicine in Houston. The center is funded by the
Agricultural Research Service, the
primary science research agency of the U.S.
Department of Agriculture.
Led by Judy M. Hopkinson, a lactation physiologist and assistant professor
of pediatrics at Baylor, the researchers scrutinized postpartum changes in the
bone mass and density of 76 new mothers during a two-year period. Half
breast-fed their infants, while half chose to feed formula to theirs. The
scientists measured bone densities at regular intervals using a sensitive bone
scan called DXA, which can detect small changes in specific bones and bone
Earlier studies suggested that breast-feeding may lead to a loss of bone
that could later increase the risk of osteoporosis. In fact, decreases of 4 to
6 percent in lumbar spine bone mineral density (BMD) during lactation have been
shown. Nursing mothers lose about 210 milligrams of calcium each day in their
breast milk, which can trigger bone loss in areas prone to fractures later in
Hopkinsons study confirmed earlier ones suggesting that new mothers
who formula- feed do not experience decreases in bone mass or density. She
found bone loss only in breast-feeding mothers. However, she also found that
women who breast-fed had complete bone recovery by two years after delivery.
Those who breast-fed for nine months or less had nearly 3 percent more bone
than right after delivery, while those who nursed up to 24 months also gained
bone, but at a slower rate.
Hopkinson believes that this bone loss and recovery cycle allows the nursing
mothers body to repair tiny flaws in her bones, making them stronger than
they might otherwise be. She is now monitoring bone densities in women before
and after giving birth, to learn more about how pregnancy affects maternal bone
ARS is the U.S. Department of Agriculture's chief scientific research