May 29, 2017
422 The Brain-Gut Axis [29 May 2017]
Last week we looked at how our gut microbiome affects our immune system. This week we’ll discuss how it affects our brain, mood and memory. I last wrote about this topic two years ago [#320]. The network of neurons and chemical pathways connecting the digestive tract and the central nervous system is called the Brain-Gut Axis.
The brain uses this axis to monitor the digestive tract for hunger, stress, and the presence of pathogens; and to control aspects of it, including transit speed, production of mucous lining the colon, and the secretion of stomach acid, bile and pancreatic enzymes. But the signaling goes both ways – the condition of the digestive tract, including the bacteria living in it, also influences the brain.
Justin and Erica Sonnenburg in their 2015 book The Good Gut devote a chapter to this connection and share findings from some of their animal experiments. Lab mice specially raised to have a bacteria-free gut lacked the caution that helps wild mice avoid predators, and scored lower in memory tests than mice with normal gut microbes. Other experiments showed that transplanting gut bacteria from anxious mice to calm mice increased their anxiety (and vice versa) along with measurable changes in their brain biochemistry.
One way that the gut bacteria influence the nervous system is by the chemicals they produce which get absorbed into the bloodstream. Some of these chemicals have a beneficial effect like the short chain fatty acids mentioned last week. An estimated 90% of our serotonin, the “feel-good” neurotransmitter, is produced in our gut with the help of certain bacteria. Other bacteria-produced chemicals are toxic and have undesirable effects. An example is EPS, which was found to be greatly elevated in mice with autistic-like behavior; the behavior improved when different bacteria were introduced which normalized the EPS levels.
Research holds the promise of modifying our microbiome in the treatment of not only inflammation related chronic diseases like MS and Inflammatory Bowel Disease (IBD), but also mood disorders like stress, anxiety, depression, and even neurological conditions like autism, ADHD, OCD, and schizophrenia. This is one field of research that I plan to keep an eye on. More next week.
For more information on this or other natural health topics, stop in and talk to Stan; for medical advice consult your licensed health practitioner.