Question: My wife is a La LecheLeader and she has been asked for
information on breastfeeding and osteoporosis. Someone
who had been on long term Heparin has been diagnosed
with osteoporosis via Technicium scan (she has a couple
of compression fractures), and is considering weaning
her newborn because of bone mass loss from breastfeeding.
Does anyone out there know how much bone mass is
typically lost from breast feeding??? I know it is
reversible, but that is all
Answer:
Multiple pregnancies that come with very little time between pregnancies
are considered a risk factor for osteoporosis because of the
increased calcium requirement during pregnancy (50% increase, RDA goes from
800 mg per day to 1.2 grams per day). But during pregnancy, there are
changes in maternal hormones that help to protect the bones from calcium
loss so long as the dietary intake of calcium is increased, especially
since the absorption of calcium increases from an average of 27% before
pregnancy to 57% during pregnancy.
During the last trimester however, there is a net loss of calcium from the
bones inspite an increased calcium absorption and increased calcium intake.
This net loss of calcium seems to be caused by prolactin. A normal
pregnancy will result in about a 2% loss of bone calcium. During the
last trimester, fetal uptake of calcium exceeds the amount that can be
absorbed from the gut (primarily because gut absorption decreases during
the last trimester due to very high prolactin levels which seem to supress
1,25diOHvitD levels).
While breastfeeding, calcium intake has absolutely no effect on the calcium
concentration in the breast milk and unlike during pregnancy, there is no
improvement in calcium absorption. The low estrogen while breastfeeding
and the high prolactin combine to drive calcium from the bones into breast
milk. Dietary calcium and even exercise do not appear to be able to stop
this extensive calcium loss while breastfeeding. 6 months of breastfeeding
results in a 5% loss of bone calcium. 12 months gives a 10% loss of bone
calcium. Losses of less than 10% prior to the age of 30 are not considered
to be significant risk factors for osteoporosis because with proper diet
and exercise, the woman can gain all of this back (assuming that she has
time to recover between pregnancies).
After the age of 30, it is much harder to put any lost calcium back into
bone. Space travel in a weightless state also causes extensive calcium
loss from bone. The rate of calcium loss from bone in space is 0.5% per
month. Time in space is now dictated by the recoverable calcium (do not
stay long enough to loose more calcium than you can recover once returning
to Earth). For men, this has been about 5%. We are now trying to gather
data for women (estrogen appears to enable women to get a better regain of
lost calcium than what we see in men).
