Asked by: Edward Seymour, Hove
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.
Dr Emma Davies is a science writer and editor with a PhD in food chemistry from the University of Leeds. She writes about all aspects of chemistry, from food and the environment to toxicology and regulatory science.