Why does eating spinach make my teeth feel weird?

As well as being a great source of iron, spinach is packed full of oxalic acid. When you chew spinach, calcium in your saliva reacts with the oxalic acid to create insoluble calcium oxalate crystals. These stick to your teeth and make them feel gritty or chalky. You may feel that drinking milk might help but its high calcium content will only make things worse. The good news is that spinach does not damage your teeth. In fact, calcium oxalate crystals are used in some dental treatments claiming to eliminate sensitivity by targeting dentine, which lies below the enamel.