It could be the sugar alcohols, but it could also be your body adjusting to a big change in what's coming in (or both). Anytime there's a drastic change in diet, the body can react with either constipation or diarrhea. The remedy for either is the same: more fiber!
You can get plain psyllium husks at pharmacies or health food stores or you can get psyllium caplets or tablets. It's also important to get plenty of fiber from the foods that you eat (veggies!) and plenty of water, epsecially if you have diarrhea and plan to add the psyllium.
The changes in bowel habits are usually transitory and will probably clear up in a week or so once your body adjusts to the new dietary regime. It's still a good idea to make sure that you're getting plenty of fiber and water even after the symptoms clear up, though.