Why do fake sugars make us poop?


For anyone who’s chewed too much sugar-free gum in one sitting or has seen reviews of sugar-free gummy bears, you know that certain types of sweeteners can lead to bathroom events on par with Tunguska 1908.


Many people accept that sugar alcohols can lead to bloating, gas, and diarrhea, but few seem to know why. Are these sweeteners toxic and your body is rejecting them? Do they get drunk and throw a party in your colon? Should we really eat it at all?

Getting to the “bottom” of it

As it turns out, the effects of sugar alcohols come from their inherent properties. These sweeteners resemble real sugar, but with what is chemically known as an alcohol group attached. (No, they don’t contain what we normally think of as alcohol—which is ethanol. However, both sugar alcohols and ethanol contain the alcohol chemical group.) Types of sugar alcohols include erythritol, mannitol, sorbitol, and xylitol, and while these sweeteners vary widely, there are a few general trends they usually share.

First, they’re lower in calories, taste only slightly more sweet than real sugar (as compared to artificial sweeteners, which tend to be in the 160 to 600 times sweeter range), and often have little to no effect on blood sugar levels, unlike regular sugar—hence their popularity. And second, they’re difficult to digest and absorb; the bacteria in the mouth can’t use them at all, so sugar alcohols are popular in gum to keep the bacteria from destroying your teeth.

The second part is the most important when it comes to emergency bathroom trips, as the lack of digestibility is at the heart of the problem. For example, if you were to consume 20 grams of maltitol (the stuff in those gummy bears), around 44% of that wouldn’t get absorbed by your upper intestine. When this enters the colon, the bacteria there have a field day fermenting the stuff, producing carbon dioxide and methane—and leading to flatulence and abdominal discomfort.

If you eat a lot of a sugar alcohol, the capacity of the bacteria in the colon to ferment may become overwhelmed. In this case, the undigested sweetener causes water to be drawn osmotically into the colon, resulting in sudden, watery stools.

The good news

There are three easy ways to avoid these issues with sugar alcohols— don’t eat them; eat them with other foods to dilute the concentration; or eat them in increasing amounts, which allows you to build up a tolerance to them. If this seems like more trouble than it’s worth, remember that sugar alcohols generally have good side effects. As mentioned before, they’re usually low-calorie and low-glycemic index, making them popular with dieters and diabetics. Beyond that, some have other benefits.

Xylitol in particular seems to have beneficial side effects. It has been shown to prevent plaque buildup and cavities, along with remineralizing enamel, making it particularly popular in gum and in some toothpastes—while seeming to have positive effects on the composition of bacteria in the gut. It has been shown in multiple studies to aid in increasing bone density—a major plus for those with osteoporosis. Further, it is also believed to help prevent ear infections in children. And lastly, it may boost collagen production—meaning skin will be less likely to wrinkle.


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