I used to have more problems with IBS when I ate a lot of meat. Since I changed my diet to more organic foods and more fruits and vegetables, I don't have that constant battle anymore. I have tried "activa" with not much result. I use protein shakes made from Nature Plus brand, Spiru-ten.
I love the blueberry and cream flavor, which I mix with almound milk or soy milk, with fresh or frozen blueberries. This seems to help regulate my digestive tract. I thought the problem might be a lack of certain vitamins or minerals, in my diet. This brand contains rice and pea, and non-GMO soy. They have lots of favors to pick from like plain vanilla or chocolate, or tangerine dream, etc... When I used it with regular milk I had IBS problems, but with soy or almound or rice milk it mixes easier in my blender. This is my pick, but there are many brands out there for you to try. I have also used unflavored yogurt to prevent yeast problems. I hope this helps you in some way.