Asked by: Alex Fletcher, Margate
The taste buds on your tongue are covered in proteins that act as receptors for food particles. When in contact with food and drink, these receptors send a message to your brain, evoking one of the five taste sensations: sweetness, sourness, saltiness, bitterness, or umami.
When you brush your teeth, the toothpaste releases a foaming agent called sodium lauryl sulphate (SLS). This SLS interferes with the proteins that line the membranes of taste cells in the mouth. This impairs the tongue’s ability to taste sweet flavours, replacing them with an unpleasant, bitter sensation. The SLS also destroys bitterness-suppressing phospholipids, allowing the bitter taste to take over, resulting in the unique and horrible flavour you experience when you eat or drink something after you have brushed your teeth.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.
