If you drink your tea "straight," you may want to add a dash of milk the next time you enjoy a cup to keep your pearly whites shining. A professor at Alberta's School of Dentistry found that a splash of milk significantly reduces tea's ability to stain teeth.

Ava Chow found that casein, the main protein in milk, binds to tannins, a polyphenol found in tea that is responsible for much of staining.

"Tea is the second most consumed drink in the world, and the way it’s processed affects how teeth are stained," said Chow. "The more the tea is processed or oxidized, the higher its staining properties are. But we’ve found that the addition of milk to tea reduces the tea's ability to stain teeth."

Chow used extracted human teeth with no cavities, fillings, cracks, or other flaws. She and her students first recorded and determined the color of the natural teeth using a VITA Easyshade Compact Dental Spectrophotometer.

The teeth were then divided and placed in either a solution of tea, or a solution of tea with milk for 24 hours at 37 degrees. The colors of the teeth were then measured a second time.

"The results we found showed that casein is the component of milk that is responsible for the reduction of tea-induced staining," Chow said. "The magnitude of the color change observed in our experiments is comparable to the color change seen by vital bleaching products and more effective than whitening toothpastes."

The study was published in the International Journal of Dental Hygiene.