Go into almost any store that sells sweets and you'll find a rack of candies labeled sugarfree. "Great" you may think. "The manufacturers are finally producing sweets I can eat without making my blood glucose (BG) go up."
If you look at the ingredients of these products, you'll find out that most of them use maltitol in place of regular sugar. So what is maltitol?
Maltitol is a sugar alcohol, which means that one of the groups in the molecule has been chemically altered. (For those interested in the chemistry, it means that an aldehyde or ketone group has been reduced to an alcohol group.) The alcohols usually end with -itol.
But maltitol is a disaccharide, meaning that it contains two sugars hooked together. One of those sugars is sorbitol, which is a sugar alcohol. In most people, sorbitol doesn't raise BG as much as glucose. But the other sugar in maltitol is glucose.
This means that when you eat maltitol, 50% of that maltitol is glucose.
Table sugar is also a disaccharide. In this case, half the molecule is glucose and the other half is fructose, so the glycemic index (60) is just about halfway between that of glucose (100) and that of fructose (19). The glycemic index of maltitol is about 70.
This means that when you eat something sweetened with maltitol, you might as well be eating something sweetened with table sugar in terms of how much your BG levels will increase. The difference is that half of the table sugar is fructose, which you might want to avoid because it can increase triglyceride levels, and half of maltitol is a sugar alcohol, which can have other problems such as producing gas and diarrhea.
How can the candy manufacturers get away with labeling something "sugarfree" when it contains glucose? That's because the legal definition of "sugar" is sucrose, or table sugar, and the candy does not, in fact, contain sucrose.
So buyer beware. When you see a sugarfree product on the shelves, look at the ingredient list. There are other non-sucrose sweeteners. Stevia has the least effect on BG, but stevia-sweetened candies are expensive. A sugar alcohol with a relatively small effect on BG is erythritol. Other sugar alcohols raise BG in some people and not in others. It depends on your digestion.
If you want to see how a particular product affects you, try some and test one or two hours after you eat it.
If the ingredient list includes maltitol, put it back.