If you eat protein bars, or low sugar foods, you’ve probably seen sugar alcohol listed among the ingredients in many popular brands.
Sugar alcohols are found most commonly in food products labeled “sugar-free,” including hard candies, cookies, chewing gums, and soda, but have recently become very popular in “health foods”.
Do you really know what you’re consuming? Is sugar alcohol bad for you? The short answer to the latter question is “no”, sugar alcohol is not bad for you, but it is not intrinsically healthy either.
What Is Sugar Alcohol?
Sugar alcohol gets its name because of its molecular structure, which is a hybrid between a sugar molecule and an alcohol molecule. Biochemically speaking, sugar alcohols are structurally similar to sugar but are either poorly digested (e.g., maltitol), or poorly metabolized (e.g., erythritol).
Sugar alcohol has grown in popularity as a “sugar replacement” in foods such as protein bars because they contain few calories, minimally impact insulin levels, are safe for those with diabetes, and are better for your teeth.
Here’s a list of some popular sugar alcohols so you can identify them when you look at a nutrition label:
- Erythritol
- Maltitol
- Hydrogenated starch hydrolysates
- Isomalt
- Lactitol
- Mannitol
- Sorbitol
- Xylitol
The two major sugar alcohols found in protein bars and most low sugar foods are maltitol and erythritol, which are explored in more detail below.
Sugar Alcohol #1: Maltitol
Maltitol, the more popular of the two, has only 2.1 kilocalories per gram (compared to 4 for sugar) and is comprised of glucose and sorbitol (see image on right).
Only 80% as sweet as sugar, maltitol has 47% fewer calories…and won’t rot your teeth! The downside of maltitol is its poor absorption. In high doses, it will cause a laxative effect (i.e., diarrhea). This isn’t a concern in protein bars with less than 20 grams, but down a couple of the bars with over 20 grams and you might spend the afternoon in the restroom; fortunately, most companies are listing sugar alcohols directly on the label.
If “sugar alcohols” aren’t listed as a separate category under carbohydrates, check the ingredients list. You shouldn’t have to look very far because sugar alcohols will be one the first ingredients on the list.
Safety & Metabolic Effects of Maltitol
One study estimated the maximal safe dose to be 30 grams.1 40 grams caused very mild GI upset, but still no diarrhea. Furthermore, if you’re watching your weight, take comfort in the fact that maltitol causes minimal insulin secretion. This is important for maintaining blood sugar, which is a significant factor in controlling your body’s hunger. In the figure to your right, the response to 50 grams of either glucose (solid lines) or maltitol (dashed lines) is shown.2
For the record: 1) 50 grams is far more than what is found in any food products; and 2) these volunteers exhibited no side effects to 50 grams of maltitol, suggesting that the 30 gram limit mentioned above might be person-specific (i.e., some people can tolerate more than others).
Last but not least, maltitol promotes healthy gut bacteria!3
Sugar Alcohol #2: Erythritol
Erythritol, another popular sugar alcohol, is: 1) virtually calorie-free (0.2 kcal/g); 2) not a laxative; and 3) still 70% as sweet as sugar.
Erythritol is used in foods because its physical properties mimic sugar. It’s not more widely used because it has a slight cooling effect, kind of like mint, which is undesirable in some foods. This can be countered by the addition of inulin,4 a super-fiber that promotes healthy gut bacteria and I suspect companies who are trying to reduce the carbs in their protein bars will be doing more of this in the future…less sugar and more super-fiber, what more could you ask for?
Safety & metabolic effects of Erythritol
Erythritol lacks maltitols laxative and pro-gut bacteria effects because it is almost completely absorbed (~90%).
One group looked at the insulin response to a chocolate snack containing either erythritol or sugar.5 The figure to your right has been color-coded and edited for simplicity. Red = 24 grams of sugar; blue = 48 grams of erythritol.
After breakfast (Time = -2 h), which was identical in both groups, insulin went up to a similar degree confirming that subjects in both groups had a normal insulin response. After the snack (Time = 0 h), however, insulin only increased in the subjects who ate the sugar-containing chocolate (red line). And at twice the dose, the erythritol-containing chocolate snack was probably much sweeter. As mentioned above, unlike maltitol, erythritol has no GI side effects… it’s almost completely absorbed. But the other half of the story is that it is excreted almost completely intact (it’s not metabolized by the body, which accounts for its lack of calories). Did I forget to mention erythritol has virtually no calories?
So Should You Eat Sugar Alcohol?
While sugar alcohol might be better for you than actual sugar (what wouldn’t be?) it is still not intrinsically healthy. If you’ve got an insatiable craving for something sweet, sugar alcohols are the lesser evil, but in terms of healthy-eating, you would be much better off grabbing a piece of fruit than downing a protein bar full of this stuff.
