The Gut-Brain Axis: The Science of the Link Between Gut and Mental Health

The Gut-Brain Axis: The Science of the Link Between Gut and Mental Health

I'm always interested in learning about how food affects my body, mind, and soul.

I really believe that the food we eat deeply impacts our quality of life, ranging from healthy joints to healthy thoughts to a healthy perspective of health. What we put into our body literally forms our body: our cells are composed of the building blocks of our energy sources. The quality of these building blocks, therefore, affects the quality of our foundation. Think of it like building a house- if you use crumbly, weak bricks, you will have a crumbly, weak building. If you're trying to build a house that will literally last you the rest of your lifetime, wouldn't you take the time to find the highest quality materials?

An aspect of health that is often overlooked is gut health. We tend to not think of our guts as being particularly complex or intricate, being mostly a place where food gets broken down and then passed along. Doesn't seem like a terribly complex process, but the truth is, our entire intestinal tract is lined with a network of neurons that studs the walls of our stomach, intestines, esophagus, colon, and rectum. We call this the "enteric nervous system", and it is so incredibly vast that scientist Dr. Michael Gershon has taken to calling it Our Second Brain.

Because of the network of neurons, your brain has a direct link to your stomach. For example, simply the act of thinking about food releases digestive enzymes into your stomach to prepare for food consumption. And those butterflies you feel in your tummy when you start to get nervous? That's the smooth muscles in your stomach reacting to the "fight or flight" messages your brain is setting off. There are 100 million neurons that forge the connection between your brain and your gut, and we call this connection The Gut-Brain Axis.

Your brain controls all of your actions by sending messages to the nerves in your body. Quite a bit of your brain's messages are targeted toward the vagus nerve, which controls the innervation, or the supplementation of nerves, of your digestive tract. Mental states that are stressful to your body, such as depression, anxiety, or even anger decrease your brain's activity, and in turn, decreases the activity of the vagus nerve. Dr. Sarah Ballantyne describes the results of this depression by saying, "This will reduce pancreatic enzyme secretion and cause poor gallbladder function, thereby reducing stomach acid production, as well as decrease gut motility, decrease intestinal blood flow, and suppress the intestinal immune system."

Now, if this suppression of the vagus nerve is chronic, as it is for many Americans who are constantly under stress of some sort, your stomach processes will slow down quite a bit. This can result in SIBO, or Small Intestinal Bacterial Overgrowth. When SIBO occurs, yeast and pathogenic bacteria in your gut gets way out of control. This isn't the cool bacteria that we want to get from fermented foods like sauerkraut and kombucha. This is bacteria that we don't want in our guts.

When the bad-guy bacteria is excessively present in our intestines, it increases our gut-permeability. A leaky gut is something I've discussed before in Food and Mood Pt. II, but in essence, it means that the contents of your stomach (including partially digested food, stomach acids, and pathogenic bacteria) start to seep out into the rest of your body. This causes chronic, low-grade inflammation that can cause serious health problems such as Irritable Bowel Syndrome and autoimmune flair-ups.

A screwed-up stomach sends screwed-up signals back to the brain. In fact, according to Dr. Ballantyne, 90% of the fibers in the vagus nerve carries information to the brain from the gut, not the other way around. In fact, evidence shows that the brain is communicated to directly by the gut, having a direct impact on mood and emotions through the nervous system. When the gut is permeable and leaking, inflammatory cytokines (chemical signals of inflammation) travel through the blood stream straight to our brains. This means that they cross the blood-brain barrier, causing inflammation in your brain. Not good.

When the brain is inflamed, your body becomes stressed, creating a vicious cycle for the whole leaky-gut-inflamed-brain thing you've got going on.You're not imagining things if you experience digestive distress during stressful parts of your life. Things like travel, mental health issues, and even a big argument with someone you care about can directly affect your digestion and absorption of your food.

The best thing you can do you aid your stomach health and repair your gut lining is to carefully examine your diet. Foods like grains and legumes contain lectins that are highly abrasive to the lining of your intestines. Foods like collagen-rich broth, probiotic kombucha, and nutrient-dense organ meats are great for repairing the damage and patching you back up. I'll write more on the specifics in subsequent posts, but for now, check out Food and Mood and Food and Mood Pt. II for more science-y stuff.