Are there any safety concerns with sugar alcohols?

Sugar alcohols are regulated as either GRAS or a food additive. The FDA has filed GRAS affirmation petitions for isomalt, lactitol, maltitol, HSH, and erythritol. Sorbitol is on the GRAS list, while mannitol and xylitol are listed as additives.
The reason that sugar alcohols provide fewer calories than sugar is because they are not completed absorbed in our body. For this reason, high intakes of foods containing some sugar alcohols can lead to abdominal gas and diarrhea. Any foods that contain sorbitol or mannitol must include a warning on their label that "excess consumption may have a laxative effect." The American Dietetic Association advises that intakes greater than 50 grams/day of sorbitol or greater than 20 grams/day of mannitol may cause diarrhea.
The presence of sugar alcohols in foods does not mean that you can eat unlimited quantities. Sugar alcohols are lower in calories, gram for gram, than sugar. They are not calorie-free, and if eaten in large enough quantities, the calories can be comparable to sugar-containing foods. You will need to continue reading the food labels for the calorie and carbohydrate content regardless of the claim of being sugar-free, low-sugar, or low-carb.

What are nonnutritive sweeteners?
The use of nonnutritive sweeteners began with the need for cost reduction and continued on with the need for calorie reduction. Since the 1950s, nonnutritive sweeteners have become a weight-loss wonder that allowed us to have our sweets without the calories and cavities. These sweeteners are also referred to as intense sweeteners, alternative sweeteners, very low-calorie sweeteners, and artificial sweeteners. The celebration and consumption of nonnutritive sweeteners came to a halt in the '70s when cancer connections were discovered. To this day, there is a great deal of controversy surrounding the safety of nonnutritive sweeteners. For every compelling positive argument in favor of using these sweeteners, there is an equally compelling negative argument opposing their use.
The five FDA-approved nonnutritive sweeteners are saccharin, aspartame, acesulfame potassium, sucralose, and neotame. Each of these is regulated as a food additive. These sweeteners are evaluated based on their safety, sensory qualities (for example, clean sweet taste, no bitterness, odorless), and stability in various food environments. They are often combined with other nutritive and/or nonnutritive sweeteners to provide volume that they lack on their own and a desired flavor. An Acceptable Daily Intake (ADI) for each additive has been established. The ADI is the amount of food additive that can be consumed daily over a lifetime without appreciable health risk to a person on the basis of all the known facts at the time of the evaluation.