Can the bacteria in your gut ease your troubled mind?

Lately we’ve explored the role of the vagus nerve in transmitting communications between the central nervous system, or the brain, and our enteric nervous system located in the gut. The vagus superhighway can help or hinder us, depending on our ability to act versus react when presented with stressful situations. We can choose to let our stress response, the vagus nerve, and gut instinct guide our reactions, or we can consciously direct these innate interactions in a controlled, thoughtful manner. Consciously directing the gut-brain link can greatly benefit us by maintaining focus and reduction negative impacts of stress.

But in some situations, no amount of conscious effort can influence the messages being transmitted or overcome how we react to them. The relatively new field of neurogastroenterology, which studies the gut-brain connection, has experienced a significant increase in research interest as a growing number of scientists observe very real neural consequences resulting from changes in the gut microbiome. It appears the enteric nervous system housed in the bowel plays a much larger role in our daily lives than simply directing digestion.

The enteric nervous system, with its 100 million neurons and utilization of over 30 neurotransmitters, behaves much like our central nervous system in its production, transmittal, and uptake of biochemical messaging. Autism provides an example of similarity between the central and enteric nervous systems. The genes responsible for synapse formation between neurons in the brain are also involved in synapse formation within the enteric nervous system, which may explain why many autistic children experience digestive motor abnormalities and have elevated serotonin levels.

In fact, 95% of the body’s serotonin can be found in the intestine, which also explains why irritable bowel syndrome frequently correlates with the administration of antidepressant medications called selective serotonin reuptake inhibitors. The artificial inhibitors block intestinal serotonin reuptake which causes an abundance of that particular neurotransmitter and sends digestion awry.

The biochemical methods of the central and enteric nervous systems seem interchangeable in many capacities, but the bowel uniquely houses a microbiome within its walls that appears to wield previously unimaginable power. Most of us are familiar with the presence of gut bacteria and the role they serve. Our guts either have a well-balanced population with plenty of helpful bacteria to keep our systems humming along normally, or we experience some level of bad bacteria overpopulation and digestive upset.

What most of us don’t realize is the neurogastroenterology community has discovered the gut microbiome, with its roughly six pounds of helpful and hurtful bacteria, reaches beyond the immediate bowel environment to also influence the brain. At UCLA, researchers compared bacteria present in an individual’s gut with their brain structure as depicted by MRI. The study found that connections between brain regions varied based on the dominant gut bacteria species. Further, they demonstrated consumption of probiotic-laced foods like yogurt can change brain function including reducing reactions of anxiety circuits.

Since these initial small-scale studies, there have been many focused experiments on mice including administration of antibiotics, isolated probiotic strains, transplanted microbiomes and diets intended to shift the microbiome balance. Each study yields intriguing results that further supports a gut-brain connection. Anxious mice receiving transplanted bacteria from fearless counterparts grow calmer and more fearless. Aggressive mice eating gut-influencing diets relax. Mice exhibiting autistic or stressed behaviors no longer present these symptoms after receiving probiotics. Healthy mice dosed with a parasite that induced gastric inflammation and anxiety were subsequently relieved of their symptoms via 10-day Bifidiobacterium longum administration.

No one asserts that rodent experiments prove humans will experience identical outcomes, but these are strong indicators of positive results and the neurogastroenterology community is understandably excited. Imagine if we had the power to reduce or eliminate mental health issues with simpler, natural alternative therapies like clinical dosing of isolated probiotics. Already, small-scale human studies have yielded desirable results. In the UK, researchers administered a 30-day course of Lactobacillus helveticus and Bifidobacteria longum to healthy volunteers with the intent of reducing anxiety and depression. In this case, the results matched expectations, although no one totally understands why.

Investigations continue to better understand the biochemical processes behind the results and extent targeted experiments to larger-scale human test groups. Clearly, the gut-brain-microbiome alliance is highly interactive which makes it especially challenging to analyze and comprehend. But since 90% of vagus nerve fibers conduct messages from the gut to the brain and not the opposite direction, our gut constantly informs our brain and influences our state of mind. Hopefully someday, we will better understand the relationships and communicate better with both systems.

— Embrace hope.

Do you regularly take probiotics for mental or general health purposes? What improvements have you noticed?

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Rebounz: a start-up with a mission to instill hope in people experiencing mental health struggles around self-worth, grief or uncertainty. Want to receive updates? Join our mailing list.

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