That green juice you sip every afternoon could have an unexpected side effect: Stained teeth! Fresh-pressed juice blends made with dark leafy greens and beets contain plant pigments called chromogens… But they can build up on teeth – and as little as one juice a day could cause stains. The effect is a lot greater when you sip the juice, instead of just eating those foods. So sip through a straw so it doesn’t come in contact with your teeth.