The Use of Directed Probiotics in ME/CFS: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

This clinical study aims to evaluate the use of i3.1 probiotic in participants who meet the Institute of Medicine (Canadian Consensus Criteria) case definition for ME/CFS and who may or may not be diagnosed with irritable bowel syndrome (IBS). The main questions it aims to answer are: * how effective is the usage of the i3.1 probiotic to reduce gastrointestinal (GI) inflammation and normalize the GI and systemic/brain interface? * how well is it working on IBS severity? The study sample is 100 male and female participants aged 45 to 70 years with ME/CFS (per the Canadian Consensus Criteria); one-half of the participants will have co-morbid IBS (per Rome IV criteria). Participants will receive an i3.1 or a placebo and be assessed at baseline, at eight weeks, and at 12 weeks (four weeks post-treatment completion).