The gut brain axis is the collective term for all the channels of direct and indirect communication now known to exist between the brain and the intestinal tract, providing a pathway for thoughts and feelings to influence the operations of the intestinal system and for the state of the viscera to affect all the ways the brain works. Over the past few decades, researchers have discovered that the brain and the gut communicate in many more ways than once thought and they talk about many things, fr
How the Gut-Brain Axis Works
The gut talks to the brain constantly and rapidly. There are direct connections between the gut and the brain, the major one being the vagus nerve . The gut also produces neurotransmitters that relay messages to the brain. There are many indirect ties, such as short-chain fatty acids, substances produced by bacterial action in the gut that act on nerve pathways or circulate to the brain or stimulate processes that affect the brain. These activities are currently under intensive research, because they suggest new ways of approaching treatment of both psychiatric conditions and gastrointestinal problems.
Vagus means wandering, and the vagus nerve , the longest in the body—reaching from the brainstem to the abdomen, with branches to all the visceral organs—is a prominent component of the gut-brain axis. The vagus nerve oversees many body functions—heartbeat, for one—but as the main highway connecting brain and gastrointestinal tract, it sends information about the state of the gut to the brain, delivering it to important information about, say, hunger, or the need for specific nutrients.
In the course of digesting food, the bacteria of the microbiome produce many substances that act on the nervous system. Chief among them are neurotransmitters—including serotonin and GABA—known to be involved in many psychiatric disorders. There are many other neurally active substances produced in the gut as well, and they send signals to the brain via the vagus nerve or are directly transported to the brain by the vagus nerve. In addition, the vagus nerve brings to the brain news of the body’s inner sensations, an awareness known as interoception. Because it is a two-way road, the vagus nerve is also a pathway by which thoughts and feelings affect the operation of the intestinal tract.
The therapeutic implications of this understanding are huge. The vagus nerve can be used as a channel for improving disordered brain function; manipulation of the microbiome by diet is one significant way. It is also possible to directly target the vagus nerve as treatment for both psychiatric disorders and such somatic conditions as irritable bowel syndrome and inflammatory bowel disease.
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