This is part 2 of the gut-brain connection series. Please read “The brain and the gut are intimately connected!” before this one so you understand exactly how the gut and the brain are connected. (Found further below on my Facebook page or in the comments.) Now that you see the clear connection between the gut and the brain, you might be wondering, what exactly is coming from the gut that affects the brain?
The answer is in the microbiome and the metabolites they produce. We are hosts to trillions of bacteria. We have about 6 pounds of bacteria in and on our body at all times! Some estimates say we have 10x as many bacterial cells in our body as human cells, and up to 100x the amount of bacterial DNA then human DNA!
This truly means we are only 10% human. We live in a symbiotic relationship with them. Certain byproducts that we release as part of our normal metabolism, they use as food and fuel and vice-versa. We both could not live without each other. We either have a diverse and balanced microbiome that produce positive things for us like short-chained fatty acids, hormones and neurotransmitters, otherwise we have an unbalanced microbiome which is known as dysbiosis.
A dysbiotic microbiome produces compounds that can damage us and create inflammation if they get into our bloodstream like ammonia, D-lactic acid, lipopolysaccharides, peptidoglycans and more. Let’s start with how an imbalance or dysbiosis of our microbiome can negatively affect our mental health. Certain bacteria are responsible for maintaining the health of our gut lining. If these bacteria are not present such as during dysbiosis, then our gut lining is comprised and we are at chance at developing enhanced intestinal permeability also known as leaky gut.
There are many other factors that can contribute to leaky gut as well such as processed foods, gluten, NSAID pain relievers, stress, alcohol, antibiotics, foods with no fiber such as animal products, and many other things. Our gut microbiota also feed off of the soluble fiber found in plant foods, so if you are not consuming much fiber then the microbiota will actually start to feed off of the lining of your intestines instead which can cause leaky gut.
Leaky gut is a condition where the cells of your intestines that normally control what enters your blood stream and what doesn’t are compromised and spaces start to form between them, allowing things to enter your blood stream which shouldn’t be there. This is a huge topic in its own right being linked to inflammation and all auto-immune conditions, but for this article I’m going to stay focused on the microbiome.
Some of the metabolites the microbiota produce are lipopolysaccharides and peptidoglycans. Normally with a healthy gut, these stay out of our bloodstream, but if someone has a leaky gut, or what’s known as small intestinal bacterial overgrowth (SIBO), these compounds can enter our blood stream and activate an immune response which can throw off our circadian rhythm, sleep cycles and also causes inflammation throughout the body, including the brain.
Inflammation has been shown to be present in every single case of mental illness so this is definitely a contributing factor when thinking about the health of our brains. A couple other ways in which a dysbiosis can affect brain health is from unhealthy bacteria sending signals directly to the brain via the vagus nerve and from bacteria that produce D-lactate and other compounds that are neurotoxins which can enter the blood via leaky gut and then wreak havoc on our brains.
So now that the negative part is over, let’s look how a healthy and diverse microbiome can positively affect our mental health! The enterochromaffin cells that line our intestines are responsible for producing 90% of our body’s serotonin; only about 10% is made in the brain! One of the prerequisite these cells need for making serotonin is certain amino acids and short-chain fatty acids that these healthy bacteria produce.
Without these compounds from them we can only produce about 40% as much serotonin! On top of producing the precursors for serotonin, a healthy microbiome also produces dopamine, GABA, norepinephrine, BDNF (this is brain-derived neurotrophic factor which is critical for the production of new brain cells) and other neurotransmitters and hormones which are critical to our mood and mental health!
This is all pretty new information that has come out recently and it’s pretty mind blowing in my opinion. In fact, every single mental health disorder has shown to have a connection to the microbiome. Mark my words; focusing on the microbiome is the next generation of health care. We are discovering more and more about it every day and discovering its connection to virtually every dis-ease and to every physiological process in the body. So now knowing all of this, don’t you think it’s important to start taking care of your gut and your microbiome?
