The gut-brain axis is undeniable, but specific mechanisms of influence continue to be investigated. Specifically, the gut microbiota is now considered the body’s major neuroendocrine system, controlling body processes including the stress response and the hypothalamic-pituitary-adrenal (HPA) axis.  Back in the early 20th century, Nobel laureate, Ilya Metchnikoff, observed that the growth of cholera could…