Hi,
Dr. MF at Beth Israel is excellent. They have an IDB clinic (he is not part of that research group), so you could look at another doctor there. His brother is in that portion of the practice so you may even want to start with him. I've never seen him before.
Dr. F has recommended and encouraged alternate treatments like probiotics/fiber along with more traditional approaches.
Great guy. Highly recommended.
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Edited in order to keep this a bit more generic given the experience of jsummer below.