I was diagnosed with Lymphocytic Colitis in 2010. My heart goes out to you as I know how terrible it can be.
While I haven't confirmed it with a biopsy, I consider myself cured at this point. That's the nice thing about LC, they do feel it can be cured unlike Crohn's and I do believe I am one of those lucky ones.
I personally believe that there are a variety of cause of Lymphocytic Colitis. It makes sense really. All LC really is, is a bunch of lymphocytes that have been hanging out in your intestinal tissue for a long time leading to some inflammation and all the fun associated with that.
The problem then arises of figuring out what is the underlying cause. I went through a multi-year experiment of changing everything from diet to pretty much every environmental variable I could and seeing if that helped.
What made the most difference?
One stretch.
I drove my wife and myself crazy changing every variable in our lives and in the end, all I needed was a stretch. A stretch that it took me only 3 years to figure out. CT scans, colonoscopies, countless blood tests, and all I needed to do was a specific stretch.
Seriously. One very specific yoga stretch made all the difference in the world for me. As crazy as it sounds, I believe my excess lymphocytes were a result of tension in specific areas of my body not allowing my body to function properly. Sorta like a kinked garden hose. To this day I will once in awhile start to feel that old twinge, do the stretch for a couple days in a row, and be fine.
It's not something I really mention because if someone would have told me, when I was at my worst, that a single stretch would make all the difference, I might have punched them in the face. And I feel bad saying it on this forum considering people with Crohn's could probably do all the stretches in the world and it wouldn't make much difference. But none of that changes the fact that it is the truth for me.
I believe, for me, what the doctors saw under their biopsy was a microscopic manifestation of a macroscopic issue. It would be like looking at car engine pistons under a microscope and seeing microscopic abrasions when the real issue is no oil in the engine.
Do I believe this is the cause of most people's LC? Definitely not. It could be dietary, it could be environmental, it could be genetic, it could be stress related, it could be a combination. I don't know. And that's one of the things that really sucks. There's just so little known about it.
As such, the best advice I can give is to be the world's most open-minded scientist. Form hypothesises and test them. You're your own guinea pig.