This past week I had a patient who had never heard of the gut:brain connection and so I wanted to send some info out on it. 

Over the years of working as an ND, it has been really cool to see an increase in body literacy in the new patients that I am onboarding. More and more people are coming in having heard of the “gut:brain connection” and processes like “leaky gut”. 

I spend so much time on education, especially in the first few visits, that it expedites things when some of these terms and concepts aren’t brand new (I sometimes need to pump the breaks when I start to get that 👀 look).

So, what is the gut:brain connection? (please stay with me because this is SO important to know for your health & wellbeing).

The gut-brain connection is no joke; it can link anxiety to stomach problems and vice versa. Have you ever had a “gut-wrenching” experience? Nervous butterflies in your stomach? Do certain situations make you feel nauseous or sick to your stomach?

The gastrointestinal tract where our enteric nervous system (ENS) lives – sometimes referred to as the “second brain” – is sensitive to emotion. Anger, anxiety, sadness, elation — all of these feelings (and others) can trigger symptoms in the gut. Many people get this but they may not know the connection goes BOTH WAYS. A troubled intestine can send signals to the brain, just as a troubled brain can send signals to the gut. Therefore, a person’s stomach or intestinal distress can be the cause or the product of anxiety, stress, or depression.

Last week I emailed you about the vagus nerve. I wanted to follow through to explain how the vagus nerve plays a critical role in the gut:brain connection, as it is the primary conduit through which signals are sent between the gut and the brain. The ENS, located in the walls of the gastrointestinal tract, contains over 100 million neurons that communicate with the central nervous system (CNS, aka brain and spinal cord) via the vagus nerve, which sends signals back and forth between the gut and the brain.

One of the ways in which the gut-brain connection is thought to function is through the release of neurotransmitters, hormones, and other signalling molecules that are produced by the gut. 

For example, the gut produces several hormones that play a role in regulating appetite, hunger, and cravings:

The gut produces a hormone called ghrelin, sometimes called the “hunger hormone” because it signals to the brain that it’s time to eat, while another hormone called leptin produced primarily by fat cells signals that the body is full and plays a key role in metabolism and insulin sensitivity to prevent metabolic disorders like obesity and type 2 diabetes.

Other hormones that signal to the body that you are full and should stop eating include Peptide YY, Cholecystokinin (CCK), and Glucagon-like peptide 1 (GLP-1). Oh, and I can’t forget insulin! High levels of insulin like we see in “insulin resistance”, prediabetes, or type 2 diabetes, can stimulate hunger and cravings for sugary or high-carbohydrate foods.

And last but not least, CORTISOL: produced in response to stress, it can have a significant impact on appetite and cravings, namely for high-fat, high-sugar foods.

In addition to regulating appetite, hunger, and cravings, the gut-brain connection also plays a role in regulating mood and behaviour. Here are a few of the key players in this connection, that are produced in both the gut and the brain:

Serotonin: About 95% of the body’s neurotransmitter serotonin is produced in the gut by our bacteria and is involved in regulating mood, appetite, and sleep. Serotonin is one of four “happy hormones” your body produces, along with dopamine, oxytocin, and endorphins. This one study found that something as simple as eating commercially available yogurt (a fermented or probiotic rich food) twice a day reduced participants’ physiological reaction to stress: yogurt eaters reacted more calmly to a series of images than the control group, as seen on brain scans. 

Dopamine: Dopamine is a neurotransmitter that is involved in regulating decision making, motivation, reward, learning, attention, memory, mood, and movement. Dopamine is released during reward-motivated behaviors such as eating certain foods, having sex, or doing any activities that you enjoy. It is part of what makes you feel proud when you complete a task (do you ever write something down on your to-do list that you already did just so you can tick it off? ) and is a major player in addictions. As you can see, it can drastically drive behaviour. Again, our gut bacteria make about 50% of the body’s dopamine.
GABA: GABA (gamma-aminobutyric acid) is an inhibitory neurotransmitter that is involved in regulating anxiety and stress. It has a calming effect and is thought to dampen nerve cell hyperactivity linked to fear and anxiety. GABA also plays a role in sleep and is related to attention and alertness. The go-to sleep medication Zoplicone increases GABA; this is also the main target of anxiety medications from the benzodiazepine class, generally given out sparingly for panic attacks due to their habit forming nature. Neither gut derived serotonin, dopamine, or GABA cross the BBB (blood brain barrier) but are thought to act on the brain via the vagus nerve. Some studies on the effects of probiotics have demonstrated that gut bacteria increase levels of GABA in the brain via the vagus nerve.

OK, so all this to say that if you struggle with depression, anxiety, brain fog or trouble focusing, poor memory, addictive behaviours, altered appetite or hunger cues, sleep issues, or simply feeling blah due to low motivation, consider whether we need to tackle something going on at the level of your gut (i.e. imbalances in the microbiome, gut inflammation, etc.).

If you think this could be you, book in to discuss how to start figuring out this piece of the puzzle!