The Science Behind “Spinach Teeth”
Why Does Spinach Make My Teeth Feel Weird? The Science Behind “Spinach Teeth”
Spring is here, which means salad season is back in full swing. And if you’ve ever crunched through a fresh spinach salad only to notice a strange chalky, gritty feeling coating your teeth afterward, you’ve experienced what scientists and food writers have taken to calling “spinach teeth.” It’s one of those everyday mysteries that most people shrug off — but there’s some interesting science behind it, and as your dental team, we couldn’t resist explaining what’s actually happening in your mouth.
It’s All About Oxalic Acid
The culprit is oxalic acid, a naturally occurring chemical found in many plants, but one that spinach (Spinacia oleracea L.) tends to contain in higher concentrations than most other crops, according to Jim Correll, a professor of plant pathology at the University of Arkansas. Spinach likely uses the acid as a defense mechanism against insects and other animals that try to eat it. (Live Science)
When you chew spinach, the oxalic acid reacts with calcium from the spinach itself and calcium ions in your saliva to form calcium oxalate, an insoluble compound that coats your teeth and produces that familiar chalky sensation. (Compound Chemistry) As Correll described it to Live Science, it’s almost as if tiny crystals are floating around in your mouth — and that’s exactly what’s giving you that unusual feeling and texture. (Live Science) The key word there is insoluble. Because calcium oxalate crystals cannot dissolve in water, their formation creates a gritty physical barrier that lingers on your teeth until you rinse, brush, or it naturally clears away on its own.
Is It Harmful to Your Teeth?
The short answer is no. The overall pH of spinach is close to neutral, which means it is unlikely to erode your enamel. In fact, the oxalic acid has already bound tightly to the calcium and iron within the spinach itself before it ever reaches your teeth, which limits its ability to draw minerals out of your enamel. Interestingly, researchers have explored whether the same calcium oxalate crystal formation that causes spinach teeth might have applications in reducing tooth sensitivity, a reminder that the chemistry happening in your mouth after a salad is more interesting than it might seem. For now though, the science on that is still developing. (PubMed, ResearchGate)
Spinach Isn’t the Only Offender
Rhubarb is another oxalic acid-containing plant that can cause a similar sensation. (Compound Chemistry) Beets, rasberries, almonds, chocolate, and tea also contain significant levels of oxalic acid. (WebMD)
How to Reduce the Effect
Boiling or steaming spinach helps reduce calcium oxalate content. Alternatively, squeezing lemon juice over fresh spinach works because the ascorbic acid (vitamin C) in lemon juice helps dissolve some of the oxalic acid. You’re still ingesting it, but it reduces the film on your teeth. Pairing spinach with calcium-rich foods like cheese or yogurt also helps because the calcium in those foods binds with the oxalic acid before it reaches your teeth, which is why dishes like creamed spinach or a spinach salad with feta often don’t cause the same sensation. A quick rinse with water after eating raw spinach is another simple option.
Sources:
Brunning, A. “The Chemistry of Spinach: The Iron Myth and ‘Spinach Teeth.'” Compound Interest, 2018.
Geggel, L. “Why Do Your Teeth Feel Weird After Eating Spinach?” Live Science, 2016.
Jaiswal, S.K. et al. “Regulation of Oxalate Metabolism in Spinach.” PMC / NCBI, 2021.Cunha-Cruz, J. et al. “Dentin Hypersensitivity and Oxalates: A Systematic Review.” PMC / NCBI, 2011.
The information presented on this website is for general informational purposes only and does not constitute medical or dental advice, diagnosis, or treatment. Reliance on any information provided on this site is solely at your own discretion. For medical emergencies or specific health concerns, consult a licensed healthcare provider or seek emergency medical care.
