There are plenty of people in heavy metal detox groups who report CFS, and messed up gut ecosystem. Some of them reported impressive gains after detox plus other interventions such as support for methylation, adrenals, healthier gut balance, etc.
Once a person has started eating a healthy Diet and has detoxed sufficiently I wonder if a "gut make-over" could be done. I suppose some people use Miracle-Mineral-Supplement since it kills such a wide variety of microorganisms, unfortunately, both beneficial and less desirable ones.
I assume probiotics and prebiotics will be important.