My husband has fairly regular extended bouts of diahrhea - he s starting to think he is bother by diary products but that s just a guess. His PC physician told him to try eliminating dairy and he s done a pretty good job but it still persists. He solves the problem by taking Imodium etc and then it gets better for a while. What is the best way to figure out his problem and what type of practitioner is the best to see? He is also taking many medications for heart issues and has told his cardiologist but no solutions. He is 68 years old.