system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What gives aspartame and other zero-calorie sugar substitutes their weird aftertaste?

Edit: I've gotten at least 100 comments in my mailbox saying "cancer."  You are clearly neither funny nor original.
gpt
Sucrose is considered “clean” and has no aftertaste (clean meaning it only activates sweet receptors). Other sweeteners activate both sweet and bitter receptors. However, because artificial sweeteners are so powerful, they quickly overwhelm the sweet receptors. The bitter receptors still scale up though with greater mass for longer. That is why aspartame you consume is actually mostly filler ingredients, because otherwise you would be overwhelmed by the bitterness. 

Edit: If you are particularly affected by/don’t like an artificial sweetener feel free to avoid it.