Heather suggests that anything from dairy source such as whey protein can be a trigger. She says "In addition to fat and lactose, dairy contains components such as the proteins whey and casein, which can cause severe digestion problems. Though yogurt is traditionally recommended as an "easily digestible" dairy product because fermentation has reduced the lactose levels, even non-fat versions contain whey and casein, and should be avoided". However, like all things pertaining to IBS there are few universal rules that fit everyone so it is something you may have to try and see if it is a problem for you.
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS