The Brain’s Important Influence on the Gut

Our last post explores how maintaining a healthy gut promotes better mental health outcomes. And guess what? Since the gut-brain axis is bi-directional, the opposite is also true. The brain influences the gut in a multitude of ways, which we will be discussing in today’s blog.

Communication pathways

An extensive network of hormones, nerves, and biochemical signaling pathways facilitate the exchange of information from the gut to the brain, and vice versa. A major component of the ANS, or autonomic nervous system, called the vagus nerve, acts as a critical conduit for these continuous communications. As such, we’ve learned that the health of our gut has a huge impact on our mood and mental health. So now, let’s learn about how the brain affects the health of the gut. 

The stress response

Starting in the command center of the brain, the sympathetic nervous system triggers a response commonly known as “fight or flight” when we feel stressed. While this evolutionary survival mechanism is vital in the case of genuine threats, its pathways can become continually activated from daily stressors that aren’t life-threatening. And over time, chronic stress can result in physiological changes to the digestive system. 

The stressed-out gut

Here are just some of the ways the gut responds:

Digestive issues and motility

Digestive functions affected include:

• Nutrient absorption

• Gastric acid secretion

• Salivation

• Intestinal motility (hypermotility and hypomotility)

• Hunger levels

The sympathetic nervous system inhibits the activity of the parasympathetic nervous system. This prevents the “rest and digest” state and the proper functioning of the gut, and can even be one of the root causes of gastrointestinal disorders such as IBD (inflammatory bowel disease), PUD (peptic ulcer disease), and GORD (gastro-oesophageal reflux disease.)

Altered microbiome

Now more than ever it’s clear that a diverse microbiome is a key cornerstone of good digestive, brain, and overall health. However, changes in the brain when under stress can impact the delicate balance of beneficial and harmful bacteria that comprise it. In turn, this can have negative implications for the brain’s production of neurotransmitters, along with our immune function, and our digestive function.  

Gut permeability

The integrity of the intestinal barrier can be disturbed due to chronic mental instability. Often referred to as “leaky gut,” this phenomenon arises when the junctions between intestinal cells become compromised. This allows the passage of substances that can trigger an inflammatory response within the gut, and lead to the development of a range of gastrointestinal symptoms. 

So a healthy gut promotes a healthy brain, and likewise, a properly functioning brain leads to a gut that is running at peak performance. To learn more, check back for another chapter in this series simplifying the complex gut-brain connection.