Shailene Woodley – star of teen dystopia Divergent and The Fault in Our Stars – has come out as a clay eater. The 22-year-old, who has previously out-Gooped Gwyneth Paltrow with her tales of foraging for stinging nettles and collecting water from fresh mountain streams, told talkshow host David Letterman that she ingests clay as part of a detoxification diet. "Clay binds to other materials in your body and helps your body excrete those materials that aren't necessarily the best for you," she said.

She went into more detail for blog Into The Gloss, explaining: "My friend started 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, pees and even you, yourself, will smell like metal."

Woodley seems to have been referring to the belief that a certain form of clay, because of its negative electrical charge, can help to expel positively charged toxins from the body. But is there anything to it?

Paul Mackey, owner of Natures Cleansing Clay and the man behind the edible "living clay" product – "a green swelling" mass mined from the desert in California – says "the benefits of clay's 'full-body detoxification' are nothing short of amazing. It builds one's immune system, balances PH levels and allows the body to naturally heal itself and fight off future disease." Mackey suggests that users take it mixed with water.

But, before you start chomping on that mug you made in your school pottery class, others are less convinced. Dr David L Katz told the Huffington Post that the concept of the negative charge of clay is "meaningless".

He says that "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."

Mackey's retort? "Much of what it does is not totally explained scientifically, but there is some scientific explanation."