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Apr 29, 2023

The ins and outs of sugar alcohol

Health Sciences Sugar substitutes have risen and fallen in popularity like

Health Sciences

Sugar substitutes have risen and fallen in popularity like fashion trends in decades gone by, stocking favorite foods and drinks before being eclipsed by something deemed tastier, safer, or more natural.

The latest to enter the sweetener vernacular: sugar alcohol—or, more specifically, erythritol, which can be found in drinks like Bai Water and increasingly popular light ice cream Halo Top.

Which begs the question: What is sugar alcohol, and what are the associated health risks with consuming it, if any? Octavia Pickett-Blakely, a gastroenterologist and assistant professor at the Perelman School of Medicine, explains the "alcohol" component of sugar alcohol, its relationship to sugar, and how the gastrointestinal tract responds to it in the body.

What is erythritol, otherwise known as sugar alcohol?

Sugar alcohols, in general, are a class of sugar derivatives where the alcohol is formed from fermentation of the carbohydrate. Erythritol is part of the class of sugar alcohols. Typically, the sugar alcohols end in ‘-ol,’ and that's a signal it's a sugar alcohol. Erythritol is not the only sugar alcohol; some others are xylitol or mannitol. Those originate from smaller sugar molecules that undergo a fermentation process that changes the chemical structure and results in there being an alcohol component. Erythritol is a derivative of glucose, one of the monosaccharides, or basic sugars, and fermentation can occur from bacteria, or from fungi, to form these sugar alcohols.

When you say ‘alcohol,’ you mean...?

Alcohol is a broad umbrella term that refers to the chemical structure, but not alcohol as in beers or sodas. It has some of the common chemical components.

And what you’re saying suggests sugar alcohol is related to sugar?

It's a sugar that undergoes the chemical process that converts and then ferments into a sugar alcohol.

How does the body react so differently to sugar, then, by comparison?

It depends on the sugar alcohol. Some sugar alcohols—for example, xylitol–are larger molecules, and these molecules are not necessarily digested by the human body, and when they get into the gastrointestinal tract in particular, the colon, they can attract water. An adverse effect can be diarrhea as a result of that.

Another thing that can happen to large molecules is the bacteria in the colon can ferment those large molecules and cause fermentation leading to gas formation, which can result in bloating. Erythritol is reported to not lead to those effects because erythritol is a smaller molecule, which allows it to be absorbed through the small intestine into the bloodstream, and then it's eventually excreted into the urine. So, it's not broken down the way a normal sugar molecule is, in the sense of raising your blood sugar level. But it also does not reach the colon completely intact, which is thought to be what could lead to reduced gastrointestinal symptoms.

And that's for erythritol, in particular?

Right. Compared to xylitol and mannitol.

And those other two are more likely to give you digestive discomfort?

Correct.

Then why don't more people use erythritol instead of xylitol or mannitol?

Erythritol is a newer sugar alcohol. That's one reason. Another is that, even though it occurs naturally, in fruits and vegetables, the amount is small. To mass produce it requires commercial production, and my understanding—I’m not a chemist—is it's not necessarily as easy to produce in mass as some other sugar alcohols.

Erythritol is something you’ll notably find in more recent food items, like Halo Top.

Erythritol is [also in] Truvia. So, you can buy Truvia commercially. But you don't buy xylitol by itself. You’re not going to find xylitol in a bag next to sugar in the grocery store. Artificial sweeteners you’ll find, like Sweet ‘n’ Low. You may find those, as artificial sweeteners, commercially available. But erythritol is in Truvia.

It sounds like these associated problems are more short-term than long-term?

Short-term effects. To my knowledge, erythritol is one of the newer sugar alcohols, but it's been deemed safe in humans. I ran across one study that referred to an adverse effect in the fruit fly, so it's been looked into as a potential pesticide. The flies that ingested the erythritol-enhanced food had slower neurological function, and didn't live as long. But extrapolating what happens with flies and what happens in human physiology is not something that's appropriate to do. It's similar to the controversy years back with the aspartame, or Sweet ‘n’ Low, and bladder cancer in rats. Later on, there were reports in the press about artificial sweeteners leading to cancer. It turned out rats had an increased risk of cancer related to something else, and it wasn't even the Sweet ‘n’ Low. It requires more time and study, but as of now it doesn't look like, in small and safe amounts, there are any adverse effects to be had.

And it's new?

When I say ‘new,’ I mean in terms of the U.S., in the past few decades. But it was discovered at least 100 years ago. As far as being used in food production and as a sweetener, it's relatively recent as it comes to be a common household item.

Do you ever discourage people from ingesting this sort of thing? From a gastroenterological standpoint.

I haven't had anyone specifically ask me about erythritol. In general, when I assess a patient who has symptoms, I ask about dietary consumption, and do make it a point to ask if they consume artificial sweeteners, or non-nutrient sweeteners, or low-caloric sweeteners, or if someone is drinking five or six Diet Cokes a day, or eating a lot of sugar-free gums or candy, then I advise them to try avoiding them to see if symptoms improve. In general, when I give patients dietary advice, it's trying to figure out if it's something specific they’re eating.

And what's also notable, and perhaps what's alluring for a lot of folks, is sugar alcohol doesn't spike blood sugar, right?

Interestingly, erythritol is not shown to have significant effects on your blood sugar because even though it is absorbed into the bloodstream, it does not metabolize in a way that glucose does. That doesn't mean it doesn't have an impact on insulin. So, if you think about the base of all these sugar alcohols being sugar, or a small carbohydrate, if there's some way the alcohol portion is separated from the sugar part and it ends up being metabolized back down to the original sugar, there's a possibility it can be absorbed, enter the blood stream, and raise your blood sugar that way. It all depends how much the sugar alcohol is metabolized. Most of the larger ones are not metabolized very much. But with bacterial fermentation, if there's a chemical reaction where some of the smaller sugars are cleaved from the alcohol molecules, I could conceive that it may have some effect on the blood sugar.

But in general, the sugar alcohols are advertised as not having a significant impact on your blood sugar.