He's not suggesting new parents pause in the delivery room to whip up a placenta sandwich. But neuroscientist Mark Kristal says human mothers might be missing out on the benefits other mammals receive from gobbling up their afterbirth. With luck, there might be a way for us to take advantage of placenta power that's not totally disgusting.
Mark Kristal is a professor at the University of Buffalo who's been studying the practice of placenta eating--or placentophagia, if you want to bring it up in polite company--for more than 40 years. His interest in the subject sprang from his study of maternal behaviors in mammals giving birth. "I had the field to myself," he said in an email.
And he knows it's gross. "Unfortunately, people often ask me what my research is on during dinner," he says. "It always gets a laugh (and a gag)."
Humans, with the exception of some naturopaths and celebrities, don't eat placentas. But that makes us nearly alone among mammals. From rodents to cattle to apes, new moms turn to the business of eating or licking up the afterbirth, including the liver-like placenta, as soon as the baby is out.
In a new review paper (soon to be available here), Kristal and his coauthors discuss the potential benefits of placentophagia for mammals that practice it, as well as for mammals that don't (us). There are several practical reasons why animals might ingest their placentas. Maybe they want to hide the odor of blood from predators, for example, or to keep their nests clean. Maybe mothers are famished after the ordeal of giving birth, or perhaps the placenta replaces nutrients that were depleted during pregnancy.
Though some of these explanations fit subgroups of mammals, none of them works universally. So Kristal thinks there must be a more basic evolutionary explanation for placentophagia. If almost every mammal does it, the simplest explanation is that they do it for the same reasons.
One intriguing possibility, and the strongest lead researchers have so far, has to do with pain. In the 1980s, researchers discovered that female mammals' bodies produce pain-relieving endorphins during labor and delivery. Studying rats, Kristal found that eating the placenta increased the effect of these endorphins. The placenta didn't dampen pain on its own. But rats that ingested placentas felt less pain, because they responded more strongly to their bodies' own pain relievers.
The effect also works with morphine, a similar pain suppressant. Rats that ate placenta, or amniotic fluid, experienced greater pain relief from morphine. Kristal found that the pain-relief-enhancing effect of afterbirth works in male rats, too, and in animals of other species. It also worked when researchers fed rats with human placentas.
This suggests human placentas have the same health benefits as other mammals'. So why do humans, alone among land mammals, deny ourselves the pleasures of eating placenta? It's possible, Kristal says, that evolution destroyed our appetite for afterbirth for a good reason. Maybe it has to do with toxins caught in the placenta as the organ filters them out of the fetus's environment. Or maybe extra-painful childbirth was helpful in human evolution because it encouraged women to help each other through delivery.
Kristal thinks that with further research, scientists can identify the ingredient in placenta that enhances pain relief from morphine or endorphins. Then the compound can be made in the lab and used as a drug--for all kinds of pain in males and females, not just childbirth.
These days, a few women who have gotten wind of the potential advantages of placentophagia are experimenting with it themselves. But they're interested in more than just pain relief. There are claims that eating one's placenta cures conditions ranging from postpartum depression to nursing difficulties.
Though such claims aren't backed up by any research, Kristal is interested in these same postpartum problems--which, he says, are uniquely human. Sure, other mammals sometimes go so far as to kill and eat their newborns. Rodents, for example, are tempted to ingest everything that comes out of them during delivery, baby included. But a healthy newborn will get its mother's attention by moving around and making noise. Other mammals only eat their young after an extremely stressful pregnancy.
Kristal says none of these behaviors, though, are parallel to the human problems of postpartum depression or an inability to bond with one's baby. If scientists could pinpoint the mechanisms that cause these issues, they could then start asking whether any element in the placenta might help treat them.
While science lags behind, eager placenta-eaters are going ahead with their own methods. Actress January Jones recently outed herself as a fan of placenta pills. After delivering her son, she had her placenta dried and made into capsules. Pill poppers are also featured in this gruesomely detailed 2011 New York Magazine article about placentophagia. (Focused on trend-conscious Brooklynites, the story contains the horrifying sentence, "I threw a chunk of placenta in the Vitamix with coconut water and a banana.")
Mark Kristal gets emails "all the time" from women who have tried placentophagia, he says. Without exception, they all insist it helped them.
But the claims of placentophagia fans are the same regardless of how much placenta they ingested, when they took it, or how they prepared the organ (cooked? raw? encapsulated? smoothied?). And it's unlikely that any real medicinal effect of the placenta could be so universal. For example, experiments have shown that placenta loses its pain-suppressing power when it's heated.
It's more likely that the benefit human women report from eating their afterbirths is the benefit of placebo. The ability to make women feel that they're tapping into a primal force to keep themselves healthy may be the real power of placenta.
Mark B. Kristal, Jean M. DiPirro, & Alexis C. Thompson (2012). Placentophagia in Humans and Nonhuman Mammals: Causes and Consequences Ecology of Food and Nutrition
Image: avlxyz/Flickr (Note: This is a picture of someone's French toast remains. Not placenta.)