Acesulfame potassium — usually written "acesulfame K" or "Ace-K," and branded Sunett or Sweet One — is a non-nutritive sweetener about 200 times sweeter than sugar. It's calorie-free, heat-stable (so it works in baking, unlike aspartame), and passes through the body without being metabolized. The FDA approved Ace-K as a general-purpose sweetener in 1988 and set the Acceptable Daily Intake at 15 mg/kg of body weight. It has a slightly bitter aftertaste on its own, which is why it's almost always blended with another sweetener rather than used alone.
That blending is the thing to notice on labels. Ace-K is the sweetener most often paired with sucralose or aspartame — the combination masks each one's aftertaste and lets manufacturers use less of each. So a "zero sugar" drink or a flavored protein product may list Ace-K plus sucralose together. Because it's heat-stable, Ace-K also appears in more baked and shelf-stable "sugar-free" products than aspartame does. It's found in diet sodas, flavored waters, protein powders and bars, sugar-free gum, and some "light" dairy products.
For kids, the guidance is the same as for the other non-nutritive sweeteners: the AAP 2019 policy statement doesn't ban them but notes limited long-term pediatric data and the concern that early intense-sweetness exposure may shape taste preferences. The FDA reviewed multiple studies before approval and considers Ace-K safe within the ADI, which is far above realistic intake. As with aspartame and sucralose, the practical stance is moderation, and whole-food-sweetened snacks are the preferred daily default for young kids.
How to spot it on a label: "Acesulfame potassium," "acesulfame K," "Ace-K," "Sunett," or "Sweet One." Scan the ingredient list for it appearing alongside sucralose or aspartame — the pairing is the norm. It's most common in "zero sugar" sodas and flavored waters, protein bars and shakes marketed to older kids and teens, sugar-free gum, and some reduced-sugar dairy. Products sweetened only by fruit, dates, or honey skip it entirely.