Actress Shailene Woodley has added clay to her diet in a bid to be as healthy as possible.

The Divergent star explains she began making her own toothpaste with clay so she could get her daily dose after reading about the benefits of earth in her diet.

She tells U.S. late night host David Letterman, "If you look at indigenous cultures around the world, people are eating clay almost daily. It's just a part of their diet... because it's really good for their bodies...

"Clay binds to other materials in your body and helps your body excrete those materials that are not necessarily the best for you..."

The earth-loving star, 22, also studies herbalism and practices a concept called "re-wilding", which helps her connect to the plants around her and understand their benefits.