The Science of Self Care: Your Second Brain

Part II – Your Gut and Your Brain: It’s a Mutual Relationship

Have you ever experienced butterflies before a job interview or had a feeling in the pit of your stomach that something might be wrong? That’s your second brain, or your gut talking to your brain. It turns out that our guts have a lot more to say than “I’m hungry” or “I’m full.” In fact, over 100 million neurons live in the gut lining in a network called the enteric nervous system (ENS) … aka our “second brain.”¹

In Part I, we covered the mind-body health connection. This week, we’ll discuss how our second brain plays a role in our physical and mental wellbeing, and why gut health is so important. The gut-brain axis is a complex system, so let’s break it down into a few key components.

Our Gut

“Gut” is an expression tossed around in lay health literature. But what exactly are we talking about here? The term often refers to the gastrointestinal (GI) tract that begins in the mouth and runs through the esophagus, stomach, and the small and large intestine. This system of organs is responsible for digesting food and getting rid of waste. It’s also home to trillions of microorganisms in a gated community known as the microbiome.  

Our Microbiome

The microbiome consists of microbiota (good and bad bacteria), their genes, and the environment they live in. Most microbiota live in our large and small intestines. In general, the richer and more diverse the bacterial community, the better.² This impressive ecosystem impacts our digestion, immune and hormonal response, and also influences how well our gut communicates with our brain.

Our Second Brain

The Enteric Nervous System (ENS), aka second brain, is a network of neurons rooted in our GI tract. This network constantly communicates with our brain via the vagus nerve. Daily conversations may look something like this:

Second Brain: My human ate too much. Signal some hormone to make them stop!

Main Brain: Okay, I’ll tell the hypothalamus to stimulate leptin.

Or …

Main Brain: I’m stressed and sense danger, get ready to move … (like when you have a big presentation coming up).

Second Brain: Okay, I’ll shift blood away from the intestines … (which causes diarrhea).

Emerging research suggests that our gut microbiota plays a significant role in this two-way communication. Microbiome diversity contributes to the development and function of the ENS, as well as our brain’s neurochemistry.³⁻⁶ On the flip side, the brain and ENS can disrupt our microbiome via immune and hormonal responses.⁶⁻⁷ So, you can say the relationship is mutual.

Gut Health: The Second Brain Connection

It’s no coincidence that irritable bowel syndrome (IBS) is often associated with anxiety and mood conditions.8 In fact, mental health disorders affect more than half of individuals with IBS.⁹ The gut-brain axis can explain this.

The gut-brain axis affects three systems, and their messengers, each of which plays a role in the onset of many physical and mental health conditions: 

  • Immune System – Our microbiome influences the development and maintenance of the immune system.10-11 Microbiota communicate with white blood cells and have a say in the production of pro-inflammatory cytokine messengers.¹⁰ ¹² This allows our gut to fight infections and respond to food allergens. Like we discussed in Part I, acute inflammation is a healthy immune response (Remember hot pizza tongue burn?). However, excessive production of these cytokines can lead to chronic inflammation, inflammatory diseases, depression, and potentially anxiety.¹⁰ ¹²⁻¹⁴ 
  • Endocrine System – There’s no doubt that hormones influence the way we think and feel. If you have ever raised a teenager or been a teenager, then you know. Hormonal imbalance affects neurotransmitters and how we respond to stress. As discussed in Part I, the fight or flight response is normal; however, excessive stress can confuse hormonal messengers. When we are stressed, our gut lining becomes more permeable. This threatens our microbiota, initiates an immune response, and boosts our stress response system.¹⁵ An imbalanced microbiome may exaggerate this response mechanism and lead to stress-related conditions such as anxiety, depression, and IBS.¹⁵⁻¹⁶
  • Nervous System – Our microbiota is vital to the development of our second brain and helps produce several types of neurotransmitters like serotonin, dopamine, and GABA.¹⁷⁻¹⁹ In fact, more than 90% of our body’s serotonin is produced in the gut.²⁰ Imbalanced levels of these neurotransmitters are often associated with conditions like depression and anxiety.²¹ Our gut microbiota also influences BDNF expression, a protein that’s important for cognitive function and has also been linked to depression.²²⁻²⁵ With these findings, it makes sense that the second brain is now a target for innovative treatment. There is growing evidence that stimulating the vagus nerve (phone line between the ENS and brain) can improve depression, PTSD, and inflammatory bowel disease.²⁶

Why is this important?

If gut conditions are associated with mental health conditions and vice versa, then we may need to start giving our second brain a little more attention. The gut-brain axis has a powerful impact on the messengers in our immune, endocrine, and nervous systems — all essential players in the balance between physical and mental health. A happy microbiome = a happy gut = a happy human.

Actify Neurotherapies is a resource for mental health patients and providers. Some of the toughest cases are ones where treatment-resistance continues to return. We are proud to offer rapid-onset treatment options that can be integrated into the holistic treatment of mood disorders. We can act with you to develop the best care plan that considers your overall wellness. If you have a question about how this post pertains to your wellbeing, send an email to ShareWithActify@actifyneuro.com.  

Coming up next week

Part III will explore food and mood because by now you’re probably thinking “Well jeez, how can I take care of my gut and the trillions of freeloading microbiota who live there?” Hint … they eat what we eat. To keep up with this blog series, subscribe to our newsletter by entering your email address in the field at the top right of this page.

References

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Megan S. Maisano, MS

Megan is health writer and Army veteran who specializes in nutrition communications and has a background in psychology. Her academic, professional, and personal experiences have convinced her that wellbeing doesn’t simply come from food, fitness, or mental health, but a peaceful balance between the three. 
(MS, Nutrition Communications Tufts University, BS, Psychology United States Military Academy)