Microbes in Your Gut Influence Your Brain, Too
It’s not only your immune system that has a direct line to your brain. Your gut, which is teeming with microbial life, also communicates with your brain, via what’s known as the “gut-brain axis.”
In fact, in addition to the brain in your head, embedded in the wall of your gut is your enteric nervous system (ENS), which works both independently of and in conjunction with the brain in your head.
This communication between your "two brains" runs both ways and is the pathway for how foods affect your mood or why anxiety can make you sick to your stomach, for instance. However, this gut-brain connection is about far more than just comfort food or butterflies in your stomach. According to Scientific American:6
"The gut-brain axis seems to be bidirectional—the brain acts on gastrointestinal and immune functions that help to shape the gut's microbial makeup, and gut microbes make neuroactive compounds, including neurotransmitters and metabolites that also act on the brain."
This also explains why changes in your gut bacteria are linked to brain disorders and more, including depression. Jane Foster, PhD, an associate professor of psychiatry and behavioral neurosciences at McMaster University, described to Medicine Net the multiple ways your gut microbes communicate with your brain:7
“One is via the enteric nervous system, the part of the nervous system that governs the digestive tract. Also, gut bacteria can alter how the immune system works, which can affect the brain. The gut bacteria are involved in digestion, too, and the substances they make when they break down food can affect the brain.
And under certain conditions, such as stress or infection, potentially disease-causing gut bacteria, or bad bugs, can leak through the bowel wall and enter the bloodstream, enabling them and the chemicals they make to talk with the brain through cells in blood vessel walls.
Bacteria could also communicate directly with cells in certain regions of the brain, including those located near areas involved in stress and mood…”
Altering Your Gut Bacteria May Influence Your Mood
A study published in the peer-reviewed journal Gastroenterology enlisted 36 women between the ages of 18 and 55 who were divided into three groups:8
The treatment group ate yogurt containing several probiotics thought to have a beneficial impact on intestinal health, twice a day for one month
Another group ate a "sham" product that looked and tasted like the yogurt but contained no probiotics
Control group ate no product at all
Before and after the four-week study, participants underwent functional magnetic resonance imaging (fMRI) scans, both while in a state of rest and in response to an "emotion-recognition task."
For the latter, the women were shown a series of pictures of people with angry or frightened faces, which they had to match to other faces showing the same emotions.
"This task, designed to measure the engagement of affective and cognitive brain regions in response to a visual stimulus, was chosen because previous research in animals had linked changes in gut flora to changes in affective behaviors," UCLA explained.9
Interestingly, compared to the controls, the women who consumed probiotic yogurt had decreased activity in two brain regions that control central processing of emotion and sensation:
The insular cortex (insula), which plays a role in functions typically linked to emotion (including perception, motor control, self-awareness, cognitive functioning, and interpersonal experience) and the regulation of your body's homeostasis.
The somatosensory cortex, which plays a role in your body's ability to interpret a wide variety of sensations
During the resting brain scan, the treatment group also showed greater connectivity between a region known as the "periaqueductal grey" and areas of the prefrontal cortex associated with cognition. In contrast, the control group showed greater connectivity of the periaqueductal grey to emotion- and sensation-related regions.
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Originally Posted by juleswin
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