Decoded: What gives us 'spinach tooth' 

NEW YORK: Ever noticed a weird gritty film covering your teeth after eating spinach? This ' spinach tooth' is caused because of a naturally occurring chemical present in the green leafy vegetable, scientists have found.

The chemical, oxalic acid, is found in many plants, but spinach contains higher amounts of the substance compared with other vegetables, according to Jim Correll, a professor at the University of Arkansas in the US.

Spinach likely uses oxalic acid as a defence mechanism against animals, such as insects that try to eat it, Correll said.

He said the presence of other compounds, including beta carotene, lutein, folate, vitamin C, iron, phosphorous, potassium and calcium is also involved in spinach tooth.

"When you're chewing spinach, the oxalic acid combines with calcium," Correll said.

A reaction between the two chemicals can lead to the formation of calcium oxalate (CaOx), a crystal that does not dissolve well in water, he told 'Live Science'.

"It's almost like tiny crystals are floating around in your mouth, so that is what gives it that unusual feeling and texture," explaining the weird "spinach tooth" sensation, said Correll.