Why Toothpaste Makes Food Taste Bad

At some point in their life most people have made the mistake of brushing their teeth in the morning and following it up with a glass of fresh orange juice for their daily dose of Vitamin C. Assuming you've made that mistake, there's no reason to explain anymore. But if you’ve somehow gone through life without making that grave mistake: congratulations. The taste is vile. The reason for this is a simple lesson in chemistry, and the effect of Sodium Laureth Sulfate on our taste buds.

It’s easy to attribute the sour taste to the mint flavoring of most toothpastes. After all, mint and orange isn’t a great combination. Although the mint certainly doesn’t improve the taste of the juice, it’s not the cause of the very unique flavor you experience. The cause of the flavor relies on an ingredient known as Sodium Laureate Sulfate (SLS) or Sodium Lauryl Ether Sulfate (SLES), or slight variations such as Sodium Lauryl Sulfate and Sodium Dodecyl Sulfate depending on your brand of toothpaste. Also written less graceful as CH₃(CH₂)₁₀CH₂(OCH₂CH₂)_nOSO₃Na, SLS/SLES is both a detergent and a surfactant. It’s detergent property is unsurprisingly to improve the cleaning of your teeth. The surfactant property helps reduce the surface tension of the saliva and toothpaste mixture so that it can get to all the nooks and crannies of your mouth. It also gives toothpaste it’s distinctive foam, which is really only a side-effect.

So why does SLS/SLES mess up the taste of things? It does it in two ways. First, SLS/SLES suppresses our sweet-sensing taste buds from detecting sugars. Secondly, the detergent property dissolves phospholipids (fatty molecules) that live on our tongue. This means the bitter-sensing taste buds become even more sensitive. As a result when we drink things like orange juice that have a high amount of acid, and a matching amount of sugar to cover up the bitterness, we get hit twofold.

If you’re determined to drink your orange juice after brushing your teeth, there is a solution for you. You can now buy SLS/SLES-free toothpaste and avoid the unpleasantness. The trademark foam won’t be there, but it should clean just as well. As an added bonus, SLS and SLES can cause canker sores and worsen existing ones, so that unpleasantness is also avoided.

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