I’ve been on a bit of an alternative sweetener  kick these past few weeks, for good reason: people want and need to know about this stuff. While a purist shudders at the prospect of any non- or hypo-caloric sugar substitute gracing his or her tongue, I’m a realist. People are going to partake and it’s important to understand what’s entering your body and what, if any, effects it will have. Whether it’s diet soda , artificial sweeteners, stevia , or the mysterious sugar alcohols, people want the sweet without worrying about a big physiological effect – an insulin surge, a blood glucose dip, even a migraine . So I’ve been covering the various types and have tried to be comprehensive about it. As a whole, it all seems fairly safe. Alternative sweeteners might mess with some folks’ adherence to a low-sugar diet, and they might induce or fortify cravings, but the research doesn’t suggest that they’re going to give you cancer or diabetes . The potentially negative effects are all fairly subjective, so it’s safe to play around with them and determine their role in your life based on how they affect your appetite, state-of-mind, and any other subjective health markers.
One remains, however. I have yet to cover sugar alcohols. I was surprised, actually, having gone through my archives and finding nothing. Sugar alcohols are pretty prominent in the low-carb  world – all those sugar-free desserts and chocolates and protein bars geared toward Atkins types tend to use sugar alcohols – so I had better get to it, huh?
What Are Sugar Alcohols?
A sugar alcohol, also known as a polyol, is an interesting type of carbohydrate. Its structure is kind of a hybrid between a sugar molecule and an alcohol molecule (hence the name “sugar alcohol”) and, for the most part, our bodies do a poor job of digesting and breaking down sugar alcohol in the small bowel. It’s also sweet to the tongue and resistant to fermentation by oral bacteria, meaning sugar-free gum manufacturers employ it judiciously to sweeten their products without causing cavities. Our colonic bacteria , however, can and do ferment the stuff. For that reason, it’s a kind of prebiotic that, as Kurt Harris points out , can stimulate diarrhea and exacerbate existing irritable bowel syndrome -related symptoms. Common side effects of sugar alcohol consumption (or over-consumption) include bloating, gas, and abdominal pain. Sugar alcohols are not quite non-caloric, but all contribute fewer calories than sucrose, and their effects on insulin and blood sugar  (if any) are pretty minimal.
Sugar alcohols pop up in nature, in fruits like apples and pears, but any commercial product that contains them must list the specific alcohols in the ingredients. If they aren’t counted toward the official carb count, they must be listed separately in the nutritional information. Let’s look at some of the popular ones you’ll be encountering:
Xylitol – Glycemic Index of 13
Xylitol is one of the more popular sugar alcohols. It tastes remarkably like sucrose, has about half the calories, and is 1.6 times as sweet, with little effect on blood glucose and none on insulin levels . You can find xylitol in certain berries , corn husks, mushroom fibers, and oats; most commercial xylitol comes from hardwood and corn. Xylitol has a cooling effect on the mouth and is actively protective against dental caries  (as opposed to merely being neutral or non-contributive, like the other sugar alcohols), making it the favorite choice of sugar-free chewing gum makers.
There appear to be some interesting health benefits to xylitol, too, beyond the well-established preventive actions  against dental plaque and cavities. Xylitol shows promise as a bone remineralization agent, positively affecting both tooth enamel  and bone mineral density  (albeit, thus far, in rats). I count at least ten studies  showing xylitol’s promise in the treatment or prevention of osteoporosis.
Just don’t feed it to your dog . Also, it may exacerbate intestinal distress or cause diarrhea, so exercise caution (and linger near a toilet if you’re unsure of its effect on you).
Sorbitol – Glycemic Index of 9
Sorbitol is found primarily in stone fruits, and manufacturers use it in diet sodas, sugar-free ice creams and desserts, as well as mints, cough syrups, and gum . It’s about half as sweet as sucrose, with 2.6 calories per gram (compared to sucrose’s 4 calories per gram, of course). Being a polyol, it has the potential to cause great gastrointestinal distress, especially in patients with IBS. This is compounded by its relative lack of sweetness when compared to other polyols, like xylitol; people are more likely to consume greater amounts of sorbitol to attain the desired level of sweetness and companies are more likely to use more of it.
There don’t appear to be any proactive beneficial effects with sorbitol. It doesn’t affect insulin or blood glucose, which could be good for diabetics, but there’s nothing like xylitol’s promise.
Erythritol – Glycemic Index of 0
Erythritol is almost non-caloric (0.2 calories per gram) and about 60-70% as sweet as sugar. It’s the only sugar alcohol that doesn’t appear to cause gastrointestinal distress (because the body absorbs it rather than let it pass to the colon for fermentation), it doesn’t affect blood sugar or insulin, and it cannot be fermented by dental bacteria  (and it exhibits some of xylitol’s inhibitory effect on carie-causing oral bacteria, though not all of it).
For the most part, erythritol seems pretty safe, and it’s rumored to taste very similar to sugar. Overconsumption – taking in more than your body can absorb – can result in bloating and gastrointestinal distress, but it takes a lot.
Maltitol – Glycemic Index of 36
Maltitol is very similar to actual sugar in terms of mouth feel, taste, and even cooking performance (except for browning, which it cannot do). It’s 90% as sweet with half the calories, so manufacturers love using copious amounts of maltitol in sugar-free desserts and other products. That’s all well and good while you’re eating the stuff, but what about half an hour later once all that sugar alcohol has finally reached your colon and the bacteria has started feasting and fermenting? Bloating, diarrhea, abdominal pain.
It’s right there in the name, isn’t it? Mal.
There are others, but those are the big ones. Overall, the literature shows that sugar alcohols are fairly neutral as far as blood glucose and insulin effects go. Some people may see spikes , as I’ve seen reports on blogs and in comment boards to that effect, but most people won’t. They can hit your gut pretty hard and cause problems there, especially if you’ve got a preexisting condition, but healthy people with healthy digestion (which isn’t as widespread as most people think, of course) should be okay with some here and there. Xylitol in particular seems promising, and I’ll keep my eye out for more information on that as it emerges.
If you’re doing fine without sweeteners (non-caloric, hypo-caloric, artificial, natural, whatever), keep it up. Don’t go looking for an excuse to introduce sugar substitutes. But if your desire for something, anything sweet is derailing your attempts at a healthy diet, sugar alcohols may be worth experimenting with. Give it a shot if you’re gonna and let me know how it goes.
What have your experiences been with sugar alcohols? They get a bad rap from being used in so many processed “low-carb” treats , but have they helped or hindered your path to health? Let me know in the comment section!