It's happened to everyone. You brush your teeth and take a swig of orange juice. It tastes bitter and disgusting. But why does toothpaste make orange juice and other foods taste like a bitter pile of trash?
The answer is pretty simple. Toothpaste contains a detergent called sodium lauryl sulfate or SLS. It's in the vast majority of toothpaste. It helps to create that foamy feeling and, importantly to this conversation, it helps to break down fats.
SLS does strange things to your taste buds while it works its magic. Taste buds have receptors for sweet, bitter, and umami, which is a receptor for savory tastes. There are also two ion channels that detect when things are salty or acidic, which is interpreted by your brain as sourness. SLS does two things here. It blocks the taste buds that detect sweetness and breaks down phospholipids, a type of fat, on your tongue. Those phospholipids inhibit how much bitterness you are able to taste.