Summer, 1999
Understanding breastfeeding supply and
demand
 A
nursing baby with an insatiable appetite can cause a first-time
mom to doubt more than justher sanity. But, a simple lesson in supply
and demand can provide reassurance that her hungry infant is doing
exactly as nature intended.
"Sudden increases in infant appetite and feeding frequency
should not alarm breastfeeding moms," said Darryl Hadsell,
a Ph.D. scientist who studies mammary cell response to lactation-related
hormones and nutrient availability at the CNRC.
"Increased demand sets up a biological chain-reaction that
ensures a mother's milk production keeps pace with her infant's
needs for growth and development," he said.
According to Hadsell, the laws of physics require that the concentration
of lactose, the milk sugar, remains constant in breast milk. This
means that a mother's body naturally increases milk volume when
it steps up production of lactose.
"Lactose production inside milk-producing cells is tied to
the synthesis of a key protein that helps turn blood sugar into
lactose," Hadsell said. The production of this protein, called
alpha-lactalbumin, is under the control of hormones that are released
in response to nursing.
Increased feeding frequency causes more of a hormone called prolactin
to be released into a mother's bloodstream. This hormone, along
with insulin and substances called glucocorticoids, turn on alpha-lactalbumin
production, which causes more lactose to be made and leads to greater
milk volume.
According to Hadsell, this cascade of events, from demanding infant
to hormone-induced increased milk volume, continues until milk supply
meets demand. Once it does, infant hunger, feeding frequency--and
family life--generally return to normal.
However, a new mom who isn't aware of this natural progression
might doubt her body's ability to meet her hungry child's needs
and begin supplementing with formula. While this might give temporary
relief, it can intensify breastfeeding problems in the long run.
"Feeding formula interrupts the nursing cycle and reduces
breast emptying, which permits a build up of another protein involved
in regulating milk production called the Feedback Inhibitor of Lactation,
or FIL," Hadsell said.
A build-up of FIL reduces the sensitivity of milk-producing cells
to prolactin, which cuts alpha-lactalbumin and lactose production.
"In the short-run, the effects of FIL on milk volume are reversible
if exclusive breastfeeding is soon resumed. But, if the situation
becomes chronic, FIL is thought to trigger an actual reduction in
the number of breast cells capable of producing milk," he said.
"While this is normal during the weaning period, it is not
desirable otherwise."
"A new mother can trust her body to respond to her infant's
changing nutritional needs if she simply allows her infant to determine
the timing and duration of feedings," Hadsell said.
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