"Should Pregnant Women Take Calcium Supplements to Lower Lead Levels?"
Although our skeleton "has predominantly
been considered a storage site
for sequestering absorbed lead,
bone is not simply an inert storage site.
Once deposited in bone, lead can be
remobilized from bone" back into
the bloodstream if we lose bone,
for example, osteoporosis.
Even just normal menopause can do it,
rising lead levels as our bones
start to lose their integrity.
But it's the mobilization of
long-term stores of lead
from maternal skeleton during pregnancy
and lactation that's the biggest concern.
So to maintain maternal lead levels
as low as possible during this critical
period, we need to minimize bone loss.
How do we do that?
Well, "habitual excessive salt intake
could be a factor in promoting bone loss."
So is there a relationship between
maternal sodium intake and blood
lead levels during pregnancy?
We didn't know until this study.
They did find that higher salt intake
was associated with higher lead levels,
but only for women who were getting
less than 840 mg of calcium a day.
This suggests "that adequate calcium
with low sodium intake may play
a beneficial role in decreasing the blood
lead concentration in pregnant women."
Higher calcium intake has been associated
with lower blood lead concentrations
during pregnancy, but you don't know
if it's cause and effect,
unless you put it to the test.
What if you gave women calcium supplements?
We explored previously how milk
may actually make things worse.
What about just straight calcium,
especially for women
with low calcium intake?
These poor African women, getting only
350 mg of calcium a day, just 35%
of the 1000 milligram RDA.
Let's step in and give them
a whopping 1500 milligrams
of calcium a day.
That will protect their bones.
How did they ever get along without us?
Without the calcium, just getting 350 mg
of calcium a day in their diet,
they lost some bone in their spine
and hip, but the group we gave,
in our wisdom, 1500 mg of calcium
a day to, lost even more bone!
Those women who had received
the calcium supplements had a
significantly lower bone mineral
density at the hip and greater bone
loss in the spine and wrists.
Oops.
What happened?
It looks like we messed up
their body's natural adaptation.
Remember?
They were only eating
350 mg of calcium a day, so their body
wasn't stupid and was maximizing
absorption, minimizing loss.
And then we step in with calcium pills
and undermine the whole process,
turn off those adaptations,
leave their body thinking they were
always going to get these massive doses.
And then when the study stopped,
they went into major calcium deficit
and had to steal more from their bones.
The researchers went back later
hoping they'd catch back up,
and while the women lucky enough
to have ended up in the placebo group
bounced back, those given the extra
calcium continued to suffer the effects.
What about in Western women,
though, already taking in
over a 1000 mg a day?
Would giving them
an extra 1200 mg a day cut down
on some of that bone flux?
Yes, it did seem to cut down
on bone resorption by about 16%,
and thus may constitute a practical
intervention to prevent the transient
skeletal loss associated
with childbearing, which could
release any lead trapped there,
but you don't know
until you put it to the test.
This is a different paper
from the same study.
The researchers measured
what was happening to their
lead levels, and that drop in
bone borrowing led to a drop
in lead release, and so may help
lower exposure to the fetus,
as well as the infant as the
benefits continue
through breastfeeding.
OK.
But these were women
living in Mexico City,
who may have been exposed
to lead-glazed ceramics, with
lead levels approaching 10.
What about for women with
lead levels closer to the current
U.S. average: under 5?
We don't know, until you
put it to the test.
Well, half the breastfeeding women
were randomized to take 500 mg
of extra calcium a day.
Their lead levels started out
the same during pregnancy, but
shot up during breastfeeding,
as presumably some of the lead
was released from their bones.
But that was in the regular,
non-supplemented group.
In the group that got the
500-a-day calcium supplement,
there was no spike in lead in their
bloodstream, providing evidence
"that calcium supplementation
during breastfeeding may be effective
in limiting mobilization of lead from
bone stores, thus reducing the risk
of lead transfer to the
nursing infant through breast milk."
Now breast is still best regardless.
Supplementation or not, the risks
are outweighed by the benefits
of breastfeeding, but calcium
supplementation may help reduce
any risk even further.
Of course, better to not build up
lead in your bones in the first place.
As a famous occupational medicine
paper put it half a century ago,
yes, there's all methods
of dietary interventions.
There's only one way and one way only
to prevent lead poisoning: not get
poisoned in the first place.
Anything else just diverts attention
from treating the underlying cause.
For other toxic heavy metals like
mercury, for example, that would mean
advising women to avoid the consumption
of fish-that-eat-other-fish during pregnancy,
and when breastfeeding to decrease
mercury levels in breast milk.
In fact, maybe even before pregnancy,
women of childbearing age, period,
so you don't build up mercury
in your body in the first place.
For lead, that means not living
next to a smelter plant,
avoiding smoking.
Now, there's one other way
to detox your body of lead
to protect some of your future children,
but it's not ideal.
Remember that menopause study,
where postmenopausal women
had higher blood lead levels
than premenopausal women?
Well, even higher still were
postmenopausal women
who never had children.
"The postmenopausal increase
in lead levels was less in women
with prior pregnancies," presumably
because they had already detoxed
some of their lead into their children.