GUT AND MOOD: THE MICROBIOME IN ANXIETY AND DEPRESSION

Posted by: | March 24, 2015 | Comments

One key aspect of optimal digestive health relies on its main resident: the gastrointestinal microbiome. The microbiome includes all the microorganisms that inhabit our digestive tract – about 100 trillion bacteria.

A healthy microbiome starts with a vaginal birth: as the baby transcends the birth canal, the probiotics in the mother’s vaginal fluid enters the baby’s mouth and begin their healthful colonization of the digestive tract. It is possible that the high Caesarian birth rate in the United States is a contributing factor to anxiety and depression, due to lack of probiotic transference. For this reason, promoting a healthy microbiome in the next generation may need to start with a greater emphasis on natural childbirth.

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Impressive new research is emerging every day regarding the role of the microbiome within the digestive tract lining. The digestive tract itself is a center point of the nervous system, hormonal system, and immune system. It is responsible for the balance of our molecules of emotion (ie, the neurotransmitters), and, as a result, is an important player in mood regulation. Beneficial microflora is also an important part of healthy digestion. Probiotics are known not only to help the digestion, but are key factors in obesity, hormonal balance, healthy kidney function, and much more.

HOW DOES GOOD FLORA HELP THE BRAIN?

The microbiome contributes to the bidirectional communication between the digestive tract and the brain. The autonomic nervous system, enteric (gut) nervous system, neuroendocrine system, and immune system all meet in the digestive tract and coordinate healthy physiological and psychological responses. A healthy microbiome works to boost mood in a few important ways: by generating healthy levels of brain-derived neurotrophic factor (BDNF) and the neurotransmitter gamma-aminobutyric acid (GABA), and by enhancing brain receptors for GABA. Like a warm and gentle blanket for the brain, GABA is a calming amino acid, known to calm areas of the brain that are overactive in anxiety and panic and in some forms of anxious depression.

Research has also shown that hypothalamic-pituitary-adrenal (HPA) axis dysregulation can be reversed by treatment with Lactobacillus and Bifidobacterium. This research verifies the 2-way communication between the digestive tract and the brain, and reveals how the HPA axis is modulated by the enteric microbiota.

ANIMAL STUDIES

Animal studies to date clearly show benefits of probiotic supplementation. In a mouse study, animals who received probiotics were, in general, more relaxed than the control mice. The probiotic mice had lower release of corticosterone (the murine version of human corticosteroid) in response to stress, as well as lower anxiety and depression-related behaviors. These mice were fed either the probiotic strain Lactobacillus rhamnosus or a microbe-free broth. The probiotic-fed animals showed significantly fewer stress, anxiety and depression-related behaviors than those fed with just broth. In a similar study, rats fed a combination of Lactobacillus and Bifidobacterium displayed a decrease in anxious behaviors. Two other animal studies showed interesting phenotypic effects from transplanting microbiota from one animal to another: One of these studies found that switching gut bacteria from an obese mouse to a gnotobiotic lean one increased the expression of genes involved in the stress response in the lean mouse. In the other study, oral antimicrobial-induced changes in microbiota led to increased expression of BDNF and exploratory behavior, whereas the reverse occurred (reduced exploratory behaviors) when germ-free mice were colonized with gut bacteria from these same mice.

Read more at: NDNR






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