In order to talk about the gut-brain axis, we have to start with a basic understanding of the gut and of the brain.
(As an aside, I believe health literacy, or understanding what's going on inside your body, is so, so important in understanding when and why things go wrong, making educated decisions on how to manage things on your own, and knowing how and when to seek treatment when it's needed. So try to stick with me if you can!)
In case it's been a minute since biology class, let's start with a brief review of the process of digestion.
When you eat, food moves through your mouth, where the process of digestion starts, down your esophagus, and into your stomach.
While there, acidic digestive juices work on breaking it down chemically, while the rhythmic motions of your stomach work on breaking it down physically. When it's ready, it moves next into the small intestine.
The small intestine is narrow, but it's incredibly long (approximately 22 feet!) and covered in microvilli, small hair-like projections on the surface of the intestinal epithelial cells that make its surface area somewhere in the neighborhood of 2700 square feet. All this surface area is vital to getting as many nutrients as possible absorbed from your food into the blood, including broken-down carbohydrates (monosaccharides), amino acids, fatty acids, vitamins, and minerals.
What isn't absorbed in the small intestine keeps on moving and ends up in the large intestine - which is a comparatively measly foot-and-a-half in length, but much wider. In the large intestine, the body focuses on absorbing water and a few last nutrients, like electrolytes, biotin, and vitamin K.
Most of the digested food that enters the large intestine has been reduced to fiber, water, and waste products. Fiber is actually a type of carbohydrate that our bodies cannot digest.
Fortunately, our large intestines are filled with critters that can digest that fiber - our intestinal microbiota. Our bacterial friends ferment (break down) fibers from plant foods that we eat into energy for themselves, and into short-chain fatty acids (SCFAs) for us. These short-chain fatty acids, like butyrate, proprionate, and acetate, are things that we can't produce for ourselves, but that become the main source of energy for the cells lining our large intestines (among other important functions).
By the time the continued rhythmic movements throughout your intestines have brought the waste products to the end of the line, it's been a couple of days - approximately 5 hours in the stomach, 5 hours in the small intestine, and anywhere 10-70 hours in your large intestine.
While you are focused on chewing and swallowing, your body and brain are hard at work sending and receiving messages. Multiple hormones are released by the stomach, the small intestine, and the large intestine as the food you're eating moves through your digestive system. Other digestive organs, like the pancreas and liver, are activated, and send in enzymes to help with the process of breaking down foods into their nutrient components.
After you eat, the vagus nerve, the longest and most complex of all the cranial nerves, lights up with communication between your brain and your gut, as your digestive system reports back to the brain on the meal you are digesting.
The nutrients absorbed into the body, including vitamins, minerals, amino acids, glucose (sugar), short-chain fatty acids, etc., as well as the hormones produced in the gut, can also themselves send messages to the brain. Some nutrients are able to pass through the blood-brain barrier (the "wall" separating the brain from the rest of the body and protecting it from harmful substances) into the brain, directly impacting brain function (things like increasing or decreasing levels of different neurotransmitters, increasing or decreasing inflammation in the brain, increasing or decreasing different hormones... etc.).
Additionally, problems in the gut (such as irritation and inflammation) are communicated to the brain and can lead to some pretty dramatic shifts in mood, cognition, stress, and anxiety.
This connection between the gut and the brain is obviously very complex - much more so than we can address in this one blog. But the constant two-way communication happening between these two important body systems is part of why the gut has begun to be called the "second brain" or the "gut brain" - technically known as the enteric nervous system.
It's clear from the research that we have to stop thinking about mental illness as being "all in the brain." The gut-brain axis is just one example of how interconnected all of our body systems are.
Say it with me:
Mental health is HEALTH.
Want to learn more? Reach out. I'd love to work with you. And if you're interested in future posts, be sure to sign up for updates or check back soon for more to come on strategies for using our "gut brain" to improve the health of our "main brain."
Inflammation has become a buzz word in our modern health landscape. In the biochemical reality of our bodies, it's actually a pretty complex thing, but the benefit of thinking of things from an inflammation perspective is that we can see the relationships between many conditions and diseases that we never would have connected otherwise - from depression to diabetes to arthritis.
But let's start with the reason inflammation exists. It's actually a healthy process that happens in our bodies in response to injury or infection, for example. There's a trigger, an inflammatory cascade that usually involves redness, warmth, swelling, some loss of function, and some pain, and then resolving of those symptoms as the injury or infection is healed. Inflammation can be visible or invisible, on the surface of the skin or deep within the body. Either can be perfectly normal.
But too often, when the conditions are right, the inflammation happens at the wrong time and/or doesn't do anything productive and/or doesn't go away when it should. And that's what we call chronic inflammation.
Inflammation is often totally hidden from view unless you know where to look. I like to imagine chronic inflammation as a fire, smoldering throughout a person's body, showing up in all kinds of different places and ways. As time has gone by and more and more research has been done on inflammation, we've found it connected with all kinds of diseases we might never have imagined.
All the diseases that end with -itis (arthritis, bursitis, myelitis, hepatitis, sinusitis... you get the idea) are diseases of inflammation. But then there are diseases like heart disease, diabetes, allergies, COPD, chronic fatigue, depression, irritable bowel syndrome (IBS), Crohn's disease, fibromyalgia, and many, many more.
The symptoms of these disease are variable depending on the area that is affected first. But we see a lot of commonalities in them when we start to look inside the person. Just like acute inflammation causes pain, often, so too does chronic inflammation. It may be isolated to one area of the body, or it may be wide-spread. Just like acute inflammation causes loss of function, often, so too does chronic inflammation. Again, it is sometimes specific to one area of the body or brain, and other times to the body as a whole.
From an internal perspective, we often see metabolic abnormalities (changes in the way that energy is created and stored), hormonal imbalances, organ dysfunction, elevated stress indicators (such as cortisol), dysbiosis (imbalance of the bacteria living in the gut), changes in immune function, and changes in the permeability of some of the important membranes in the body (like the intestinal wall and the blood-brain barrier).
All of these diseases are caused by a complex network of triggers. Our genetics often plays a role, but is generally not our destiny. Sometimes, there is one major trigger that sets the whole body ablaze with inflammation. Often, it's a combination of multiple factors: genetics, prenatal and early life triggers, stress (including trauma), environmental triggers, dietary and lifestyle triggers, chronic infections, and more. That means that treating just one of these factors alone is usually not enough. We have to treat holistically (the whole person).
Modern medicine tends to treat the symptoms of all of these conditions, usually with medication. But trying to heal chronic inflammation by merely treating the symptoms of chronic inflammation is like trying to put out a campfire by blowing out your burning marshmallow. It often allows people to be able to function again, which is amazing and wonderful and totally not to be discounted. And medication certainly may be a part of a holistically-built long-term treatment plan. But often, it only masks the problem in one area of the body or mind, only to see it crop up again in another area.
A better approach?
Let's dig down and find the root causes of the chronic inflammation. Let's find the underlying imbalances in the body and mind. Let's treat those, with gentle, compassionate care.
Erica Golden, RDN