I've never seen them, but if I'm guessing right, the answer should be on the packet somewhere.
A lot of these 'sugar free' items have a warning that there could be a 'laxative effect' if you eat too much of it, the vital question being, how much of said item is too much?
After being told I have type 2 diabetes, I went looking for 'sugar free' alternatives and discovered that either they tasted like crap or they had that warning on the pack.
At that point I decided that if I was going to have chocolate it was going to be REAL chocolate, just not as much as usual.