You can reverse intestinal permeability though diet. However, there is no money in it and neither is it a complicated treatment. Thus, the papers about it won't get published in prestigious journals.
I have a theory that fad diets like keto, paleo, primal blueprint, low fodmap, whole 30 (of which there are numerous people claiming they have major improvements) really work because they influence the gut biome.
Talking about low fodmap specifically I wouldnt call it fad as it has been and is being researched and has shown to be effective to help with IBS, maybe not so much for other conditions.
Personally I have found it helpful in reducing the symptoms that I have.
:thinking:
I don't know about this guy. I got that link from quackwatch.