Contributed by Dr. Steven T. Devor – Director of Performance Physiology for MIT and OhioHealth, and Associate Professor of Exercise Physiology, Department of Human Sciences, and Department of Physiology and Cell Biology, The Ohio State University
Sugar alcohols are also sometimes referred to as polyols, and are a biochemically interesting type of carbohydrate. Their molecular structures are a sort of mixture between a true carbohydrate molecule and an alcohol molecule, and hence the term “sugar alcohol” is widely used.
Unfortunately, with the exception of one popular sugar alcohol, the intestines are not very adept at breaking these compounds down into their constituent pieces and then subsequently digesting them. However, the bacteria in your intestines do ferment most sugar alcohols and for this reason they are implicated in the cause of diarrhea and can cause someone with irritable bowel syndrome to have a poor reaction. Furthermore, if sugar alcohols are ingested in too large a quantity many individuals feel bloated, have intestinal gas, or have general gastrointestinal (GI) distress.
Generally speaking, sugar alcohols are extremely sweet tasting and because they are also not broken down well by the bacteria in your mouth they are very prevalent in many sugar-free gum products. The combination of a sweet taste and almost no digestion in the mouth makes these products ideal as sweeteners for sugar-free gum, as they do not contribute to tooth enamel decay or initiate the formation of tooth cavities.
The caloric content of sugar alcohols is not zero, but it is close and far less than the calories contained in sucrose (i.e., common table sugar). Importantly, most sugar alcohols have little if any influence on insulin or blood glucose levels, which is why these sweeteners are increasingly popular with individuals who are either insulin-resistant or diabetic. Certain fruits, for example pears and apples most notably, contain sugar alcohols naturally. And sugar alcohols are also found naturally in the fibrous portion of dozens of other fruits and vegetables.
When manufactured and processed products utilize sugar alcohols as sweeteners they are required to list them separately on the nutritional label so consumers know they are present. However, in the USA even though sugar alcohols are not calorie free, they are rarely ever counted in the overall calorie contribution a processed food product has from carbohydrate.
Below is a list of the most common sugar alcohols that are found in manufactured and processed foods today.
Erythritol is virtually the only sugar alcohol with a very low GI distress rate, and because of this it has become extremely popular in manufactured and processed foods as a sweetener. Erythritol is also very often utilized in combination with other ingredients as a food additive to provide sweetness, especially with the popular stevia type of sweeteners. So erythritol provides both sweetness and a sort of “bulk” mouth feel (like table sugar), in manufactured and processed food products.
Erythritol is also a common ingredient in many sugar-free chewing gums, and has been shown by controlled research studies to actually decrease the incidence of dental caries and cavities. Chewing sugar-free gum manufactured with erythritol stimulates the production of saliva, which decreases the cavity-promoting effects of any residual sugar that may be in your mouth. And unlike processed products manufactured with other sugar alcohols, products sweetened with erythritol have very little negative GI effect when consumed in larger quantities.
Erythritol is approximately 65% as sweet as traditional sucrose but it is essentially non-caloric. It contains 0.2 calories per gram, while other carbohydrates (including traditional sugar) have 4 calories per gram. So it is essentially calorie free, and in the USA can be labeled that way. Interestingly in many European nations the food labeling requirements are that it be labeled as containing exactly the caloric content it has, 0.2 calories per gram.
Xylitol is another very popular sugar alcohol. Like erythritol it tastes remarkably like sucrose, but only contains approximately 50% of the calories as sucrose (2 calories per gram), while being nearly 1.5 times as sweet. Xylitol, like erythritol, is known to have virtually no influence on circulating insulin levels and very little effect on blood glucose levels. However, unlike erythritol, xylitol is known to cause general GI distress, bloating, and intestinal gas in many individuals.
The husks of corn, a number of different berries, and even some varieties of mushrooms contain xylitol naturally. It is produced from certain hardwoods and is a by-product of corn manufacturing. Xylitol, like erythritol, has been shown to be a protective agent against dental cavities and it is therefore also found as the sweetener in many types of sugar-free chewing gums.
Sorbitol is a sugar alcohol that is found naturally in many fruits with large seeds, like apricots, peaches, cherries, plums, and nectarines. When utilized by food manufacturers it is added to many different diet sodas and sugar-free frozen dairy desserts. It is also used as a commercial sweetener in a variety of mints and cough syrups. Sorbitol contains approximately 2.5 calories per gram, and excess consumption will lead to GI distress, especially in patients with irritable bowel syndrome. Because sorbitol is not nearly as sweet as other sugar alcohols, people tend to consume much more of it in order to obtain the desired sweetness, and that is when the GI distress issues become most pronounced. Like erythritol and xylitol, sorbtiol also has little influence on insulin or blood glucose.
Maltitol is a sugar alcohol with an advantage over the others, and that is the high similarity it shares with sucrose with respect to taste, how it feels in your mouth, and how it cooks and bakes. Manufacturers of many different processed dessert treats utilize maltitol as it is approximately 92% as sweet as sucrose with only half the caloric content. However, like sorbitol, maltitol will cause bloating, GI distress, intestinal gas, and abdominal pain when too much is consumed.
One final sugar substitute that is gaining increased popularity, and that has been utilized widely in recent years is a product called stevia. Stevia is not a sugar alcohol. Stevia is a South American herb that is harvested from the stevia rebaundiana plant, and it has been used as a sweetener for centuries.
In the USA Cargil manufactures a product called Truvia, which is a combination of stevia extract and the sugar alcohol erythritol. Stevia has no carbohydrates, is approximately 250 times sweeter than sucrose, and has no influence on insulin and blood glucose levels. Additionally stevia is not known to cause any GI distress, bloating, or intestinal gas. Stevia is utilized widely in drink mixes, many different manufactured and processed food products, and several sugar-free beverages.
In summary, while there are other sugar alcohols in the marketplace, I believe the ones outlined above are the most popular and are utilized widely by processed food and beverage manufacturers. The scientific literature is consistent with regard to the evidence that sugar alcohols have little influence on insulin and blood glucose levels. Accordingly they can be good sweetener choices for those individuals that are insulin-resistant or diabetic. However, with the exception of erythritol, most sugar alcohols are known to cause GI distress, intestinal gas, and bloating, especially when consumed in too large of quantities. My advice is that if you do not use any sort of artificial sweetener now, do not go out of you way to find a way to use these products. However, if you are trying to eliminate added sucrose (i.e., table sugar) from your daily diet, certain sugar alcohols or stevia are worth trying as a means to provide sweetness to food and beverages without greatly increasing calories.