This is not an unusual ingredient in ‘zero’ beverages for sure. But I can’t see any reason to push it into protein snacks too. That’s why it lands in our series of The potentially unhealthy ingredients in protein snacks.
There is a vast range of ingredients to use in protein snacks. However, some protein snacks makers, for some reasons, still choose these not too healthy than the opposite ones. After Ponceau 4K (also known as Brilliant Scarlet 3R and 4R, and more than 100 synonyms) to be found in Scitec Nutrition CHOCO PRO Mixed Berries White Chocolate Flavour Carbs+Protein Bar, now it’s time for another weird ingredient, Acesulfame K. I have found it in only one kind of protein bars so far, in Barebells protein bars. Potentially, they are unhealthy protein bars. And I guess it’s not too necessary to be like that.
Yes, I know. Acesulfame K, also known as Acesulfame Potassium, is widely used in ‘zero’ pop drinks. That’s the fact. However, as you’ll see in a moment, there are some concerns regarding its use. And I believe it’s not too necessary to push it into protein snacks too. Therefore, I think Barebells could do it much better indeed. Anyway, this is Acesulfame K and (nearly) everything you should know about it.
What is Acesulfame K?
Acesulfame K is a calorie-free sugar substitute (artificial sweetener).  It’s 200 times sweeter than sucrose (common sugar). It has a slightly bitter aftertaste, especially at the high concentrations. Often, it is blended with other sweeteners, usually with sucralose or aspartame. It works by stimulating the sweet-taste receptors on the tongue. Therefore, you can enjoy the taste of sweetness without consuming sugar. 
It is also often used as a food additive in baking or in products that require a long shelf life. Shelf time is the length of time for which an item remains usable, fit for consumption, or saleable.  Although it has a stable shelf life, it can eventually degrade to acetoacetamide, which is toxic in high doses.  It can be listed on food labels in a number of ways like Acesulfame K, Acesulfame potassium, Ace-K or E950. 
Is it safe for use in food?
There are some concerns regarding the safety of using Acesulfame K in food. The most serious of them are the ones that claim it could increase the risk of cancer. The first safety tests on Acesulfame K were conducted in the 1970s. Among other things, these tests indicated the compound could be carcinogenic, or cancer-causing, in rats. However, the validity of these tests has been called into question over the years. Despite that, in 1996 Center for Science in the Public Interest (CSPI) urged the FDA (U.S. Food & Drug Administration) to do more testing on Acesulfame K before allowing its inclusion in soft drinks. 
Regardless of that, Acesulfame K was approved by FDA with an ADI (Acceptable Daily Intake) of 15mg/kg BW.  Also, acesulfame K was re-evaluated by the European Union (EU) Scientific Committee on Food (SCF) in 2000.  It was authorised in the EU for food use except for foods for young children. Its ADI was specified of 9mg/kg body weight (BW). Also, according to NHS, Cancer Research UK and the US National Cancer Institute have said it does not cause cancer. 
Protein bars with this controversial ingredient.
With more than 400 protein snacks reviewed so far, we have found only one range of protein bars containing Acesulfame K. The one from Barebells. All four of them we reviewed so far have Acesulfame K in the ingredients list. What’s important, however, I wasn’t able to find on their website any information on that.  Even more, there’s no information on the ingredients list of any of their protein bars out there. Is it a coincidence?
There are no firm evidence Acesulfame K is bad for health. At the same time, no one can tell it’s 100% safe either. Therefore, what I would suggest, is to stay away from the protein bars containing this ingredient, i.e. Barebells protein bars. Potentially, they might be unhealthy protein bars. It’s enough we can find it in many other food and drinks, like ‘zero’ pop drinks and beverages. There’s no need to push it into ‘healthy’ protein bars.
P.S. There are also other ingredients in protein food you should avoid. One of them is Ponceau 4R, another ingredient that may make protein bars unhealthy. And we wrote a bit more about it here.