Anna, I've been on slippery elm powder for several years now, and it works great!
While flaring, I used to take it after each meal. Now, in remission, I just take it once after dinner.
I make a "cocktail" of it, slippery elm powder in a little water + probiotics (2 different types), and you could add a little honey if you want as well.
IMO, powder is much more effective than capsules.