May 6, 2014 9:34 AM EDT

Divergent star Shailene Woodley has been known to forage for herbs and promote natural living, but she told David Letterman her diet now includes a particularly odd mineral.

Eating clay, she said, can help your body “excrete materials.” The CBS late night host had a hard time wrapping his head around that one.

Viewers more interested in her acting than her foraging should go see Woodley in the film The Fault in our Stars on June 6th.

WATCH: Divergent: Behind-the-Scenes Interview Video with Shailene Woodley
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