<<Disclaimer: Verify this information before applying it to your situation.>> Karen Maines asked whether Diet Pepsi could be the cause of problems. I understand that the artificial sweetener sorbital is a laxative, and therefore could be the source of celiac like symptoms. Diet Pepsi may have aspartame or saccharine, but anything artificially sweetened should be checked to see if it has sorbitol. nicki humphries university of maryland medical system baltimore, md.