Its rare, but a good one all the same.
Dietary therapies tend to focus on removing items form the diet that are causing problems.
This isn't really the best way of doing things, we need to think about what is to be added when we remove something. Specifically, we tend to treat patients with weak digestion problems by having remove things from their diet that are difficult to digest. These items most frequently include dairy products, greasy fatty oil deep fried things, and finally raw vegetables. On the other hand there are many foods that are used specifically as medicinals and though it isn't the most popular therapy that has come to the West from the Oriental medicine paradigm, it is most definitely to be found. Now, there is a another healing paradigm that comes from Chinese medicine at its roots, though it has undergone a great deal of evolution.