Depends on which sweetener. It depends on the chemical structure and not all of them have the same effects in people so there cannot be general rule. Splenda seems to be OK for most people. Your mileage may vary.the -itol's like sorbitol and mannitol are often problematic but I believe that Splenda is less so for most people. Sugar alcohols (what the -itol's) are can also be found in some of the more problematic fruits like apples and pears. Foods with high levels of sugar alcohol's usually have to carry a diarrhea warning.K.