You asked "where would someone "get" iBS if they didn't have an infection". This is the million dollar question. There are indications that a genetic component maybe at play too. We will have to wait and see. The research in this area is moving rapidly at the moment. It might not be too long before we have some answers.
There are instances were constituents of foods from one group require consumption of constituents of foods from another group at the same time in order for some foods to be digested efficiently. Not sure a diet that is does not take these facts into account can be healthy in the long term. In the short term it likely doesn't matter. More importantly, the food combining diet is not aligned with known and proven dietary principles for managing IBS. That in itself is not good at least for individuals with IBS.
Anyway - we have covered this topic thoroughly now. On to the next weird topic that will surely show up on the boards shortly
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS