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Here's Why You Shouldn't Eat Clay (We're Looking At You, Shailene Woodley)

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SHAILENE WOODLEY
Actress Shailene Woodley arrives at the ELLE 20th annual "Women in Hollywood" event at the Four Seasons Hotel on Monday, Oct. 21, 2013 in Los Angeles. (Photo by Jordan Strauss/Invision/AP) | Jordan Strauss/Invision/AP

During a recent interview with beauty blog and apparent disseminator of wacky health tips, Into The Gloss, actress Shailene Woodley described clay as "one of the best things you can put into your body." Her evidence? A friend had metallic-smelling bowel movements after eating clay -- a sure sign, Woodley claims, of heavy metals leaving the body. (More on that later, but PSA: The body is able to "detoxify" all on its own -- your liver and kidneys do that for you. Pretty cool, right?)

Also, one time a cab driver told the actress that pregnant women in his community (we do not know where, he is referred to only as "African") ate clay -- a practice known to researchers as geophagy. Perhaps her driver was referring to the uncommon pica cravings some pregnant women experience. Or the practice in some indigenous communities, where food sources are scarce, of eating soil as a nutrient supplement.

"This is a practice in some indigenous cultures, and I think that probably came about because they did not have access to certain nutrients in their diet, like calcium from dairy, or iron, and there are some minerals in dirt or clay," explained TODAY Show contributor and gastroenterologist Dr. Roshini Raj. Indeed, women in communities that don't include calcium-rich dairy in their diets are more likely to eat clay, research suggests.

But there are better ways to get calcium, iron and minerals, doctors agree. And while eating clay is mostly harmless, there are some concerns about both a pregnant woman and her fetus, actually being exposed to arsenic, lead and other toxicants that naturally occur in soil. The same goes for non-pregnant people.

That's the opposite of the intended effect of so-called "healing clays," which are taking off as a bit of a wellness trend, to remove toxins, heavy metals, impurities, and chemicals that are thought to have been ingested. While there is some evidence that clays can help remove toxicants from food sources when used in a culinary context, there is no substantial medical evidence that these clays, including popular bentonite clay, remove toxins. And, anyway, most people don't need help in this regard: Our livers and kidneys, if healthy, are perfectly capable of clearing our systems of trace amounts of "impurities" from our environments.

The actress went on to explain further:

So, I've discovered that clay is great for you because your body doesn’t absorb it, and it apparently provides a negative charge, so it bonds to negative isotopes. And, this is crazy: it also helps clean heavy metals out of your body. My friend starting eating it and the next day she called me and said, ‘Dude, my shit smells like metal.’ She was really worried, but we did some research together and everything said that when you first start eating clay, your bowel movements, pee, and even you, yourself, will smell like metal.

"Removing metal from the body is not necessarily good -- iron, for example, is a metal and essential to health. So, there could conceivably be benefits, but there could certainly be harms -- and a favorable benefit/harm ratio has not been established to justify recommending this," says Dr. David L. Katz, M.D., MPH, FACPM, FACP, a HuffPost blogger and founding director of the Prevention Research Center at Yale University. Katz additionally called her assertion about the negative charge of clay "meaningless."

We don't mean to harp on the actress, whose layperson experiments are her own business. But given the reach of celebrity health claims, combined with their lack of expertise and occasionally harmful -- even deadly -- consequences, it's important to address what's informed and based in fact and what's merely the opinion of a non-medical professional. For a thorough debunking of Woodley's health assertions, head over to TODAY.com.