It’s about 200 times sweeter than table sugar, but acesulfame potassium has a sour reputation.

Also known as acesulfame K or Ace-K, the ingredient is a calorie-free sweetener found in sugar-free products. Alone, it’s a white crystal powder with a slightly bitter aftertaste.

Because of this taste, it’s often blended with other sweeteners, like sucralose (used in Splenda) or aspartame (used in Equal) — both controversial in their own right.

Ace-K can be found in:

  • soft drinks
  • protein shakes
  • drink mixes
  • frozen desserts
  • baked goods
  • candy
  • gum
  • tabletop sweeteners

The Food and Drug Administration (FDA) approved Ace-K’s use in soft drinks in 1998, increasing consumer exposure to the ingredient.

Although the FDA considers it safe, some people are convinced it has potentially dangerous health effects.

The first safety tests on Ace-K were conducted in the 1970s. The validity of these tests has been called into question over the years, though these tests were reported to indicate that the compound could be carcinogenic, or cancer-causing, in rats.

The safety tests that laid the groundwork for Ace-K’s bad reputation had several purported shortcomings, including randomization flaws, poor animal monitoring, and inadequate test duration.

However, the controversy of their results remains. In 1996, the Center for Science in the Public Interest (CSPI) urged the FDA to do more testing on Ace-K before allowing its inclusion in soft drinks.

The CSPI is among several agencies stating that although the initial safety testing of the 1970s was flawed, current research does not prove Ace-K’s safety.

The CSPI says that despite the shortcomings of early research, there are health concerns associated with Ace-K, including cancer, hormone disruption, and risks to pregnant people.

There’s also evidence that something called acetoacetamide, which is created in the body as it breaks down Ace-K, can lead to thyroid damage in lab animals.

Finally, a study determined that the chronic use of Ace-K in male mice was linked to possible changes in brain function over a period of 40 weeks.

However, even with contrary evidence from the CSPI and elsewhere, the FDA has approved Ace-K as a non-nutritive sweetener. The European Union’s consumer protection agency has also established an acceptable daily intake of 9 milligrams per kilogram of body weight.

If you take a better-safe-than-sorry approach when it comes to food additives with controversial backgrounds, it may be best to steer clear of Ace-K.

By reading the labels of the foods and drinks you purchase, you should be able to identify the sweetener. It will be listed as acesulfame potassium, acesulfame K, or Ace-K, according to the FDA. It could also be labeled under the brand names Sunnett or Sweet One.

Because it’s a nonsugar sweetener, you will largely find it in sugar-free or low-sugar products. Diet sodas may be sweetened with a combination of Ace-K and other artificial sweeteners.