Gut-Brain Axis
Like the immune system, the brain and central nervous system are linked to the the gut. Biochemical signalling occurs between the enteric nervous system in the digestive tract and the central nervous system in the brain. The longest nerve in the body, the vagus nerve, is the main information channel between the gut and the brain. Interestingly, the gut produces many of the same neurotransmitters that the brain does. Serotonin and dopamine, for example, involved in mood, are produced in the gut. Gut flora imbalances have been linked to such conditions as anxiety, autism, depression and dementia. How digestive health and the balance of gut bacteria may affect brain health has led to research on specific bacteria strains. The term "psychobiotics" was coined for prebiotics and supplemental probiotic bacteria thought to have a positive effect on both digestive health and brain function.Psychobiotics

scored better on a test to measure cognitive impairment compared with
those who drank regular milk. Another clinical trial randomly assigned patients with major depressive
disorder to receive either probiotic supplements or placebo for eight
weeks. The probiotics consisted ofLactobacillus acidophilus ,Lactobacillus casei , and Bifidobacterium bifidum (2 billion
CFUs each). After eight weeks, patients who received the probiotic had
significantly decreased total scores on the Beck Depression Inventory, a
widely used test to measure the severity of depression, compared with
placebo. In addition, they had significant decreases in systemic
inflammation as measured by hs-CRP, significantly lower insulin levels,
reduced insulin resistance, and a significant rise inglutathione , the
bodys master antioxidant. The strainLactobacillus helvetica combined with Lactobacillus rhamnosus normalized anxiety-like behavior and learning and memory impairments in immune-deficient rats with HPA-axis dysfunction.