Digestive Care Expert Brenda Watson

TAG | vagus nerve


Probiotics and the Gut-Brain Axis


The gut-brain axis involves the connection of the gut to the brain. This connection goes in both directions—from the brain to the gut and from the gut to the brain. In one way, the gut-brain axis is connected by the vagus nerve—a large nerve connecting the brain to the intestines and other organs. The vagus nerve both sends messages to various organs, and also receives messages from these organs—including the gut—to send to the brain. A new study has established the vagus nerve as a main form of communication from the gut bacteria to the brain.

In an animal model, researchers were able to show that mice fed the probiotic Lactobacillus rhamnosus JB-1 showed less stress-, anxiety-, and depression-related behaviors than did mice not fed the bacteria. Further, the probiotic mice had lower levels of the stress hormone corticosterone, and they also experienced changes in the expression of receptors of the neurotransmitter GABA (gamma-aminobutyric acid) in the brain—highlighting the ability of probiotics to directly affect brain chemistry under normal conditions.

This is an early study that will need to be replicated in humans, but studies like these pave the way for our understanding of the complexities of the gut connection. Did you ever think your gut could have such an effect on your health? If you read my blog regularly, I sure hope so!

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The gut-brain connection is an interesting one because it travels in two directions—from the brain to the gut and from the gut to the brain. For the longest time this connection was thought to only travel in one direction, from the brain to the gut, like when strong emotions trigger an upset stomach. But researchers now know that what happens in your gut has an effect on your brain.

One recent study at the Stanford University School of Medicine tried to elucidate this connection. According to one of the researchers, “Gastric irritation during the first few days of life may reset the brain into a permanently depressed state.” Genetic susceptibility also plays a role, of course, since not all stomach upsets will lead to depression, but this connection is interesting.

The gut is connected directly to the brain by the vagus nerve, and even has a nervous system of its own—the enteric nervous system. This connection between the gut and the brain allows for close communication. Many studies are finding that the gut has a major effect on the brain. I have blogged about it before. More than once.

The researchers used an animal model of functional dyspepsia, also known as indigestion, to determine that stomach irritation early in life can lead to depressed and anxious behaviors that last much longer than the indigestion itself. Their findings will lead to more studies to investigate how this gut brain connection works, and if new ways can be found to treat depression and anxiety in humans, based on the gut-brain link.

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