Add Yahoo as a preferred source to see more of our stories on Google. Close-up of butter and coffee in a mug - karins/Shutterstock Nowadays, the term "bulletproof coffee" has outgrown its origin, no ...

Over ten years ago, Bulletproof popularized mixing coffee with butter as a form of biohacking. Now the company is moving in a new direction, and hopping on a more recent trend: Cold coffee at home.