Spinach contains oxalic acid that can combine with the calcium present in the teeth, forming calcium oxalate crystals responsible for the sensation of grinding.
Spinach contains quite a bit of oxalic acid, this small molecule capable of binding to the calcium naturally present in saliva. When you chew spinach, the oxalic acid quickly combines with this calcium and forms tiny calcium oxalate crystals. It is precisely these mini-crystals that trigger that strange sensation of gritty teeth or a rough film on the teeth. These small crystals temporarily cling to the tooth enamel and give the impression that you've just bitten into chalk. Fortunately, it is a temporary and harmless sensation that disappears fairly quickly after the meal.
Spinach has a distinctive fibrous texture, with small, chew-resistant fibers that cling to the surface of the teeth. These stubborn fibers, even after being chewed for a long time, sometimes get stuck against the enamel, creating that unpleasant feeling of grinding or friction. The effect is particularly pronounced with raw spinach, whose fibers are more rigid and tough. These small plant fibers resist decomposition by saliva, compact between the dental spaces, and cause that very particular "crunching" sensation when clenching the teeth.
Spinach naturally contains oxalic acid, which, when it comes into contact with minerals like calcium present in your saliva, creates small crystals called calcium oxalate crystals. These tiny crystals then cling to the surface of the teeth, causing that strange grainy or crunchy sensation when you chew. It's a simple chemical phenomenon, completely natural, but quite bizarre in terms of mouthfeel.
The way you cook spinach clearly changes its effect on your teeth. Raw, they contain a lot of oxalic acid, responsible for the well-known unpleasant sensation of grittiness and the rough coating you sometimes notice on your teeth. By boiling them, you significantly reduce this amount of oxalic acid (most of it leaches into the cooking water): as a result, your teeth clearly feel less gritty. On the other hand, quick steaming or sautéing will retain more of these compounds, which will still give you a particular sensation on your teeth after eating. The longer you cook your spinach, the softer it becomes, which can also diminish the unpleasant sensation related to its fibrous texture.
Not everyone experiences the infamous teeth gritting after eating spinach. Some people are simply more sensitive to it than others, particularly due to their natural teeth sensitivity. It also depends on the tooth enamel: thinner or damaged enamel can easily amplify that strange sensation. Similarly, the composition of your saliva and its buffering capacity (its ability to neutralize acids) play an important role in how you perceive that unpleasant gritting. Finally, your eating habits and even some of your tooth brushing practices influence why you grit your teeth with spinach while your friend doesn’t experience it at all.
Cooking spinach in boiling water significantly reduces its oxalic acid content, thereby decreasing the tooth-grating sensation after consumption.
Some foods, such as beets, rhubarb, and cocoa, also contain oxalic acid, which explains why they can cause a similar sensation on the teeth.
Adding calcium-rich dairy products, such as cheese or cream, when tasting spinach helps reduce the unpleasant sensation on the teeth, thanks to the neutralization of oxalic acid.
The sensation of dental grinding varies greatly from person to person, depending on the individual’s sensitivity to the contact with calcium oxalate crystals produced in the mouth.
Yes, many other plants contain oxalic acid, including rhubarb, beetroot, Swiss chard, sorrel, and raw cocoa. These foods can also produce that characteristic sensation of teeth grinding, although to varying degrees.
Indeed, individual factors such as dental sensitivity, saliva composition, or the presence of micro-abrasions on the enamel can influence the perception of the crunchiness produced by spinach. Therefore, some people may experience this sensation more distinctly than others based on these personal criteria.
In general, no. Although unpleasant, the sensation of tooth grinding caused by spinach is generally harmless. However, excessive and frequent consumption of oxalic acid can slightly impair the absorption of minerals like calcium or promote kidney stones in particularly sensitive individuals.
Sure! Here’s the translation: "Yes. Blanching or cooking spinach in boiling water for a few minutes helps to release some of its oxalic acid. It is also helpful to add a bit of cream or calcium-rich products, as oxalic acid readily binds with calcium, thereby reducing its effect on the teeth."
Raw spinach generally contains higher amounts of oxalic acid, which is responsible for the gritty feeling on the teeth. By cooking spinach, some of this acid dissipates into the cooking water, thereby reducing this unpleasant sensation.
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