The Rise in Blood Lead Levels at Pregnancy and Menopause


The half-life of lead in the bloodstream is only about a month. That means if you feed people lead for about a hundred days, their blood levels go up and up. But then, if you stop, the lead levels in the blood start to drop, such that within about 30 days, their lead levels are cut in half, and in another month, cut in half again, such that by three or so months, your body is able to remove about 90% from your bloodstream.

Now, if you’re chronically exposed to lead, you can have chronically high lead levels in your blood. More than half a million kids in the U.S. have concerningly high lead levels, and “poor people in…politically disempowered communities of color” are at higher risk, regardless of age. But, if you don’t live in those communities, aren’t constantly exposed to lead, why should you care about dietary strategies to lower the lead level in your own blood, if your body is already so good at it? Even if you get exposed to lead here and there, three or four months, and 90% of the lead in your blood is gone.

Ah, but the question is: gone where? More than 90% of “lead [in our body] is stored in [our] bone,” and instead of a few months to get rid of it, how about a few decades? So, even if we moved to some like other planet, and had zero further exposure to external sources of lead, we still have an internal source of lead leaching the toxic heavy metal into our system throughout our life.

But, if it’s mostly just socked away in our skeleton, what’s the big deal? Well, if you were to lose bone, all the trapped lead could come flooding back into your system. For example, when we lose weight, we lose bone, which makes a lot of sense. I mean, heavier people have a heavier skeleton—greater bone mineral density. Their body has to maintain stronger bones to carry around all that extra weight. So, if we lose weight, do the levels of lead in our bloodstream go up as our skeleton downsizes? Unfortunately, yes; but only if we lose a lot of weight. Lose 10 pounds or so, and not much happens; but lose more like 80 pounds, and the lead levels in your blood can rise 250%.

When else can you experience bone loss? Well, osteoporosis, obviously. Women with osteoporosis can lose an average of 3% of their bone mass a year, but even healthy, postmenopausal women without osteoporosis may lose a percentage of their skeleton annually.

So, do the lead levels in women go up when they lose their periods? Apparently so. A study of nearly 3,000 women found “a…significant increase” in lead levels after menopause, “provid[ing] evidence that bone lead is in fact…mobilized into [the] blood. A major implication…is that even low level lead exposure, over a relatively long time, may result in increased body burdens of lead which would be releasable in toxicologically significant amounts during…physiological states [where your bone is in flux].” Not just osteoporosis, but, most seriously, during pregnancy and lactation.

Now, most of the calcium the baby gets comes from “increased maternal…absorption” of dietary calcium. The mother’s gut starts absorbing 60 or 70% more calcium in the second or third trimester to build the baby’s skeleton. That’s why “[w]omen’s dietary calcium requirements are not increased by pregnancy or [breastfeeding].” Your body’s not stupid; when it realizes it needs more calcium, it just absorbs more calcium. Now, when that isn’t enough, you do end up dipping into the calcium stored in your bones—but not a problem. After it’s all over, your body puts the calcium back into your skeleton, such that six months after delivery, your bone mineral density is right back where you started.

That’s why even women who breastfeed for a long time, well past those six months after pregnancy, end up with no compromise to their bone mineral density later in life—whether measured in their wrists, spine, or hips.

So, what if your body makes a withdrawal from the bone bank during pregnancy and lactation, if it ends up just depositing it all back? Because of the lead. When your body dissolves some of your bone to borrow that extra calcium, it releases the lead that’s locked in there at the worst possible moment—right when your baby is most vulnerable. That’s part of “[l]ead’s toxic legacy.”


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