Hank: Just because something is natural, doesn't mean that it necessarily offers an advantage. And according to new research, that includes eating human placentas.

There's been a recent surge in placentophagy, or the practice of eating the placenta after birth, sometimes raw, sometimes cooked, sometimes dried and packed into capsules. It's been done in some form in the U.S. since at least the 1970's, with the belief that eating the placenta can help new mothers recover from childbirth, prevent postpartum depression, and boost the production of breast milk, among other things. But the popularity of the practice has continued to peak, and this January, Kourtney Kardashian blitzed Instagram with pictures of the pills she had made from her placenta after the birth of her third child. She posted pictures of the dark brown pills with testimonies of their "life-changing effects," along with #lookitup.

So, doctors did. Researchers from Northwestern University Medical School looked up ten different studies of placenta eating in humans and other animals going back to 1950 and found no data to suggest the practice conferred any benefits to new mothers. Now it turns out the vast majority of research that's been done on the practice has focused on animals like mice and dogs, and in all of those cases the effects were inconclusive. The research also found that empirical studies of placenta eating in humans were essentially nonexistent, with just a handful of studies reporting on subjects' personal impressions of their health after eating their afterbirth. But since there are no medical guidelines for how a placenta should be prepared or eaten, let alone whether it should be done at all, the study also points out that there may actually be unknown risks that come with eating a part of your own body.

The placenta is an organ that forms in the wall of the uterus in the earliest phases of pregnancy. It's actually the only organ that the human body forms temporarily and then expels. While in its place, it supplies oxygen and other nutrients to the fetus, produces hormones that stimulate its development, filters out its waste, and protects it from bacterial infections. So while placental tissue could not be more natural, the study points out that it has been found to contain toxins like selenium, mercury, lead, and a whole host of bacteria.

So placentophagy appears to be yet another case of people thinking that something is healthy because it's natural, even though scientists don't have any idea whether it is or isn't good for you.

But you know what's probably not natural, the recent rash of earthquakes that's been happening around the central United States. That's the conclusion of a major study released this week by the U.S. Geological Survey, which sought to determine whether there's any connection between drilling for fossil fuels and earthquakes, both of which have been steadily increasing in the central U.S. since the mid- 2000's.  While previous research has studied the incidence of earthquakes around individual wells, the new study looked at more than 187,000 oil and gas wells throughout the central and eastern U.S., including some areas that have seen spikes in earthquake activity and some that haven't. And it found that areas with so-called high-rate injection wells (which force high volumes of water into the ground) were nearly twice as likely to experience earthquakes as other areas. And these kinds of wells are different from hydraulic fracturing (or "fracking") wells. Fracking involves forcing high-pressure fluids underground to break up rock formations to release fossil fuels. But the wells studied here are wastewater injection wells, which take the saltwater that's been extracted from the ground, along with all that oil and gas, and pump it back underground. Partly to force out the last traces of oil, and partly just to get rid of the water.

By mapping these wells and the incidence of earthquakes, the study found that 10 percent of all injection wells had earthquakes of magnitude 3 or higher happening within 15 kilometers of them. And the correlations were even higher among wells that injected wastewater at the highest rates of more than 300,000 barrels per month. About 61 percent of those wells were associated with earthquakes in their immediate vicinity. And it's getting worse: until 2000, only about 20 percent of earthquakes in the region were connected to wells. By 2014 that number had risen to 87 percent, all while the number of regular, non-associated earthquakes stayed about the same.

Now exactly why drilling might cause quakes isn't really clear. It could have to do with injection wells causing higher pressure underground, or with the salty water acting as a lubricant along small faults.

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