No Intolerance While Traveling. Why?

Every once in a while I receive an email like this one from Adam:

I have many digestion problems in the UK. Have done for a while irrespective of what I eat or cut out. Just returned from Thailand where I had absolutely perfect digestion the whole time. I found I could eat anything I wanted the whole time. I went there for the 1st time last year+ found the same thing. After returning to UK, same digestive problems started again. Mystery to me+ my doctor. Just wondered if u have ever heard of anything like this. My life is miserable in the uk because of this. Hope u can offer an answer or some advice.

This is almost the ultimate fantasy for those of use with lactose intolerance and other digestive problems. A place in which we can eat anything we want and not suffer any consequences. Why does it have to be so far from home and so temporary an ideal?

I have no answer. I have no clue. I can't think of any reason why lactose intolerance should behave differently anywhere in the world.

I had only one possible grasp at a thought that I could share with Adam. We do know that the bacteria that live in our colons are responsible for many of the symptoms of lactose intolerance and many additional ills. And we know that bacteria are local. We'll meet strange bacteria whenever we travel. That's the problem behind traveler's diarrhea.

But what if it also worked the other way? What if the local bacteria that you encounter every day in your water and food are the ones making you ill? Wouldn't you then feel better when you got so far away that your exposure was to a whole new set that didn't cause the same problems?

I'm grasping at straws here, I know. But it's the only faint shred of an answer I have. If you readers have any similar tales or ideas that might solve this mystery, please share them.