Your gut wants you to be happy.
TL;DR: Your gut (and its associated microbes) produce the majority of neurotransmitters in your body, and play a major part in how “stressed” (physiologically and psychologically) we feel. Taking care of our guts helps us feel better in many ways. (About 6.5 min read)
Metabolic tips for keeping your guts happy:
Get 25g of fiber a day. This increases diversity in your microbiome.
Stay hydrated! This reduces metabolic stress by allowing us to absorb food faster.
Avoid eating a lot of simple carbohydrates at once, unless you’re actively moving & absorbing those sugars. Dumping simple carbs into our guts when we aren’t moving increases metabolic stress in our intestinal cells and causes Leaky Gut Syndrome.
Your gut wants you to be happy. So how do you keep your gut happy? First, who cares if your gut is happy? You do and you care a lot because everyone hates a tummy ache. No one wants to be bloated. The sale of probiotics in North America is forecasted to reach almost $15 million in USD by 2025. People aren’t buying prebiotic and/or probiotic supplements because they taste good - those things are on the market because a lot of us want our guts to feel better and we haven’t found a sustainable way to do that yet. (Spoilers: you have to eat enough fiber and you have to take breaks to move/stretch throughout the day, and most people aren’t, and it’s leading to a lot of ppl having gut issues).
Your gut communicates with your brain through an extensive nervous system. This is called the “enteric nervous system”. Why are there so many nerves and neurotransmitters in your gut? Because you cannot stay alive without eating essential nutrients, so you sure as shit better know what you’re eating. Food also gives you information about how “stressful” the environment is.
Here we mean “stressful” in a very “basic needs” sense: Are you living in a place that has enough nutritious food to support you? Your body detects the fat and sugar content of food to help you make that decision. Are you living in a place that has a lot of parasites? Your gastrointestinal (GI) tract is VERY sensitive to different signals that say you’ve eaten something you shouldn’t have. (No, not too many slim jims on your last road trip, although that isn’t helping…)
Eating too much non-nutritious food sets off the same “danger” pathways in your body as pathogens do. Non-nutritious foods are foods that don’t contain fiber, are low-protein, low-vitamins, or high in simple carbs. They cause metabolic imbalance and set off the same signals in the immune cells in your intestines and liver cells that pathogens do.* This is one of the ways that non-nutritious foods increase inflammation and make us feel bad. Metabolic imbalance is low-key sickness.
Your gut has a lot of nerves so that you can keep things moving. Things = your body. The rest of your body moves by using the fuel from the food you eat, so you need to be able to absorb that food across your intestinal cells. Your intestines themselves also need to keep food moving through them, so the smooth muscles that line your intestinal cells need signals from nerves so they continue to contract and push food down your GI tract. If you do happen to ingest something you shouldn’t have, and your body needs to get rid of it ASAP, your gut and brain need to quickly, and appropriately, communicate with each other.
Your gut + serotonin (and other neurotransmitters!) The saying “gut feeling” is literal. The fact that your intestinal cells produce the MAJORITY of serotonin in your body is becoming common knowledge. Bacteria can modulate your gut’s production of serotonin, and your gut microbes themselves produce a wide range of other major neurotransmitters. In fact, your gut bacteria produce so many neurotransmitters that “bacterial endocrinology” was proposed as its own field of study in 1993.
Your gut bacteria also produce the majority of dopamine (the “happiness” hormone) in your body, and there is an interplay between your gut microbes, dopamine, adrenaline (aka epinephrine), and norepinephrine. Adrenaline and norepinephrine are both involved with “alertness” and will increase your heart rate. Adrenaline is released when extra cortisol is also released so that you can get moving quickly. Norepinephrine is continuously released and is the most common neurotransmitter of the sympathetic nervous system (the nervous system you aren’t consciously in control of).
Your gut microbes + mood. Wow this one is a quagmire! And we don’t know enough yet to really say anything more than you need a diverse population of gut microbes** and you need them to not be causing inflammation by trying to get past your gut lining into your bloodstream, or by making it into your blood and causing inflammation in the liver. We do know that metabolic stress is associated with depression, that a variety of mood and cognitive disorders (like anxiety and Alzheimer’s) are more common in patients with insulin resistance, and that these patients have a tendency to have reduced diversity in their gut microbiomes than healthy individuals. You increase gut diversity by eating fiber. You decrease the amount of bacteria getting into your bloodstream by reducing inflammation in your intestines since inflammation causes Leaky Gut Syndrome.
So how do we keep our guts healthy? We eat a minimum of 25g of fiber a day and we don’t dump sugar into our guts faster than we can absorb it. We stay hydrated. Basically, we maintain metabolic balance. If we want to feel good, we need to feel good in our guts.
Metabolic tips for keeping your guts happy:
Get 25g of fiber a day. This increases diversity in your microbiome.
Stay hydrated! This reduces metabolic stress by allowing us to absorb food faster.
Avoid eating a lot of simple carbohydrates at once, unless you’re actively moving & absorbing those sugars. Dumping simple carbs into our guts when we aren’t moving increases metabolic stress in our intestinal cells and causes Leaky Gut Syndrome.
*The molecues that send a “danger - pathogens!” signal to your immune cells and liver cells are called pathogen-associated molecular patterns (PAMPs). PAMPs activate a “danger” pathway that causes inflammation - rightfully so, since your immune system needs to fight an invader. The same “danger” pathway can be set off by metabolic imbalance when there are no pathogens around. This is called “sterile” inflammation and the molecules are called danger-associated (or damage-associated) molecular patterns (DAMPs).
**The first study showing that “good” bacteria reduced anxiety used germ-free mice and measured their response to a restraint stress test. Mice who were then treated with Bifidobacterium infantis showed less anxiety and “stress” behaviors compared to mice that had a germ-free intestine track as well as mice that were treated with E. coli, meaning that some specific bacteria (in this case, B. infantis) can reduce anxiety and improve stress responses.
Christ, A. et al. (2018). Western Diet Triggers NLRP3-dependent innate immune reprogramming. Cell.
Sudo, N. et al. (2004) Postnatal microbial colonization programs the hypothalamic-pituitary-adrenal system for stress response in mice. J. Physiol.
Strandwitz, P. (2018) Neurotransmitter modulation by the gut microbiota. Brain Research.