Chemical structure of D-sorbitol
Image credit: Mrgreen71 [<a href="http://www.gnu.org/copyleft/fdl.html">GFDL</a> or <a href="https://creativecommons.org/licenses/by-sa/3.0">CC BY-SA 3.0</a>], <a href="https://commons.wikimedia.org/wiki/File:D-sorbitol.svg">from Wikimedia Commons</a>

At lunchtime one day years ago, I walked into a cafeteria near the building where I was working. I wasn’t in the mood for a salad or sandwich that day, so I looked at the hot entrees. Behind the glass was a heated serving pan full of rice, and next to it another pan containing a mixture I couldn’t quite identify, though there were some clearly recognizable vegetables and on the whole it looked fairly appetizing. The “daily specials” sign was missing, so I asked the server what it was. She looked down at the food, thought hard for a few seconds, looked back up at me, and said matter-of-factly, “Ingredients over rice.” Another few seconds passed and it was clear that was the only answer I was going to get. I said, “Fine, I’ll have some of that.” It was delicious—though to this day I have no idea what it was supposed to be.

Sometimes I feel comfortable living in a state of blissful ignorance about the ingredients in my food. Other times—especially when purchasing heavily processed, prepackaged foods—I like to know that at least some part of what I’m eating originally came from a well-known plant or animal source. Lots of food products, particularly dietetic foods, list something called sugar alcohols on their labels. Whatever that is, it sounds delightfully unhealthy, so what’s it doing in foods that are supposed to support good health?

Sweet and Low-Cal

A sugar alcohol (also known as a polyol) is any one of a class of sweeteners including sorbitol, xylitol, isomalt, mannitol, hydrogenated starch hydrolysates (HSH), and several other compounds. Despite their artificial-sounding names, each of these sweeteners occurs naturally in various plants. Some sugar alcohols can be just as sweet as sugar—and almost indistinguishable in taste. Their main appeal is that they have a lower caloric value than more common sugars such as sucrose and fructose. They also serve as texturizers, lending foods the same kind of moistness and chewiness they’d have if sugar were used. And they actually reduce, rather than increase, the incidence of tooth decay. All this without the potentially serious side effects of non-nutritive artificial sweeteners such as aspartame and saccharin.

The reason sugar alcohols are lower in calories is that the body cannot digest them as quickly or as completely as sugars. Consumed in moderation, sugar alcohols have little or no effect on blood sugar level, making them appealing to diabetics looking for a sugar substitute. But this lack of digestibility also means that sugar alcohols can have a laxative effect, in severe cases even causing diarrhea.

Carb-O-Rater

The term “sugar alcohol” is somewhat misleading, as polyols are neither sugars nor alcohols. Technically, they are hydrogenated carbohydrates that, at the molecular level, have some of the structural properties of alcohols. But the fact that they are a type of carbohydrate has led to much debate among those concerned about carbohydrates in their diets. Some manufacturers subtract the amount of sugar alcohols in their products from the total quantity of carbohydrates to yield a much lower “net carb” figure for their labels. They base this practice on the fact that indigestible carbohydrates, such as fiber, cannot by definition have the same effect on the body as carbohydrates that are converted to glucose. But sugar alcohols are only partially indigestible. So some people feel they should be counted as carbohydrates in their entirety, while others feel that only half the sugar alcohol in a product should count as a carbohydrate.

If you’re the sort of person who agonizes over this stuff (I’ll interject right here that I am not such a person), you can sidestep the problem altogether by sweetening your food with stevia or monk fruit extract, both of which are calorie-free, natural sweeteners that are not sugar alcohols. But if you’re interested in reducing carbs generally or sugar specifically, and don’t particularly care about the details of carbohydrate digestibility, sugar alcohols may be a great choice.

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on August 4, 2004.