Both fresh and dried shiitake mushrooms have small low FODMAP serving size amounts. For dried, Monash University lab testing has indicated that 7 g is low FODMAP. Monash says that is about 2 mushrooms, but in our experience their size varies widely; always go by weight. The amount used in a recipe must be divided by the serving size number, of course. They are optional, but they add a fantastic depth of flavor to the dish. You don’t even have to rehydrate them! Just crumble them by hand into the liquid mixture.