A new study done at Cornell University and published in the journal Microbiome
(June 23, 2016) suggests a correlation between "leaky gut", or increased intestinal permeability, and chronic fatigue syndrome. According to the main author, "If there is damage to the gut mucosa, microbial translocation could increase, altering antimicrobial regulators and dysregulating the innate immune system."
Also exciting is the idea that lab tests looking at the microbiota of the gut and certain inflammatory markers in the bloodstream related to that may be used in the future to diagnose CFS. There are essentially big differences in the gut of those with CFS versus controls, including less diversity of bacteria and increased pathogens.
The authors don't know for sure if the altered intestinal environment is a cause or a result of the disease, so more research will be done to help distinguish that.
You can see the fascinating study here: