Table 1 Probiotics for fatigue and depression - proposed pathways - adapted from Medical Hypotheses - Logan, et al.[[2]] and Logan, et al.[[3]]

•  Direct protection of the intestinal barrier

•  Influence on local and systemic antioxidant status, reduction in lipid peroxidation

•  Direct, microbial-produced neurochemical production – e.g. GABA

•  Indirect influence on neurotransmitter/neuropeptide production

•  Prevention of stress-induced alterations to overall intestinal microbiota

•  Direct activation of neural pathways between gut and brain

•  Limitation of inflammatory cytokine production

•  Modulation of neurotrophic chemicals including brain-derived neurotrophic factor

•  Limitation of carbohydrate malabsorption

•  Improvement of nutritional status – e.g. omega-3 fatty acids, minerals, phytochemicals

•  Limitation of small intestinal bacterial overgrowth

•  Reduction of amine/uremic toxin burden

•  Limitation of gastric/intestinal pathogens (e.g. Helicobacter pylori)

•  Analgesic properties