Serotonin and the Gut: The Gut-Brain Axis
Your body communications in ways you aren’t even aware of. In fact, your brain and your gut talk to each other all the time through hormones and neurotransmitters. This is known as the gut-brain axis. This communication system between your brain and your gut is a biochemical and physical network. That “gut feeling” you get or the butterflies in your stomach… that’s real! It’s actually your brain and gut talking to each other.
Conventional medicine views the body in distinct systems and psychological stressors as independent from the rest of the body. In reality, our brains are inextricably tied to our gastrointestinal tract.
This is because 95% of our serotonin, the key neurotransmitter responsible for regulating mood, is made in your gut. A deficiency in serotonin causes depression and, in some, anxiety. In fact, the majority of antidepressants work by blocking the brain’s serotonin receptors. This frees up more serotonin to remain present in the brain.
I’m going to tell you about the super hormone serotonin, it’s role in your body, and let you in on 4 ways you can boost serotonin production in your body. (Hint: it has to do with your gut health!). So what exactly is the gut-brain axis?
The Gut-Brain Axis
As I mentioned, the conversation between your brain and gut is known as the gut-brain axis. It involves your central nervous system (CNS) and your enteric nervous system (ENS).
Your central nervous system consists of your brain and your spinal cord. It controls your thoughts and emotions, along with your breathing, heart rate, body temperature, and the release of some hormones.
Your enteric nervous system, also known as your “second brain,” consists of 200-600 million neurons that move throughout your digestive system.1
The ENS works in concert with your CNS, however your ENS regulates some gastrointestinal functions independently, such as moving food through your gut and bowel movements. Your ENS also controls the release of some neurotransmitters, including gamma-aminobutyric acid (GABA) and serotonin.2
Serotonin and other neurotransmitters travel from the gut to the brain via the vagus nerve. This is the body’s longest nerve that emerges directly from the brain. Chemical signals travel both from the gut to the brain and vice versa. Because of this, those with gut issues are at a higher risk of mood imbalances, anxiety, and depression. This is where serotonin comes into play.
Serotonin: The Super Hormone
Serotonin is one of four “happy hormones” your body produces, along with dopamine, oxytocin, and endorphins. Each of these hormones perform different functions and provide “happy” feelings.
For example, endorphins are released when exercising and are a natural pain reliever, oxytocin is released when you show affection to others or animals and gives you feelings of love, and dopamine is what makes you feel proud when you complete a task. Serotonin is the mood regulator, however it does so much more.
Serotonin acts as both a hormone and neurotransmitter. It is produced in the body, however your body synthesizes this hormone from the amino acid tryptophan, commonly found in many protein-based foods such as turkey.
A serotonin deficiency is linked with depression, and in some cases, anxiety. Many antidepressant medications are designed to block your brain’s serotonin reabsorption for this very reason. By blocking serotonin reuptake, more of this feel-good hormone is available in your brain. However, these medications often have awful side effects and don’t address the root cause of your depression.
Your gut health has a strong influence on your body’s serotonin levels. As I mentioned earlier, your gut manufactures up to 95% of your body’s serotonin.3 That means if you’re dealing with chronic digestive issues like IBS, leaky gut, Candida overgrowth, or SIBO, there’s a likely chance your serotonin production is being impaired. Having low serotonin creates a vicious cycle, as serotonin is paramount for supporting proper nutrient absorption and digestion. Don’t worry, I’ll tell you how you can boost your serotonin levels in just a minute. First, let me tell you more about serotonin’s role in your body.
Serotonin’s Role in Your Body
Serotonin is used by your body for many processes, including regulating sleep, digestion, and your mood. Here are some of the tasks this super hormone performs in your body:
Serotonin Regulates Your Mood
This “feel-good chemical” is best known for its positive effects on your mood. Healthy serotonin levels help you feel calmer, happier, more focused, and less stressed. However, when you are under stress, your body releases cortisol, also known as the “stress hormone” from your adrenal glands.
Small amounts of stress are just a fact of life and are unavoidable. The problem is, when you are under constant stress, Cortisol levels are at their highest and this leads to adrenal fatigue. Serotonin is the hormone that regulates cortisol levels. However, constant stress exhausts your body and impairs the ability of serotonin to function properly, which leads to depression.
Serotonin Supports Digestion
Remember, serotonin is used to move food through your digestive system and get rid of waste. Low levels of serotonin may lead to constipation, while high levels may cause loose, watery stools. Serotonin also influences mucous secretion in your intestines and appetite, helping your body recognize when it’s full.
Some nerve receptors are responsible for signaling nausea, bloating, and pain. Serotonin is what blocks these signals. However, serotonin levels rise when you eat something toxic or have food poisoning to quickly expel food from your body by vomiting or diarrhea.
People with irritable bowel syndrome who experience constipation often have lower levels of serotonin, or the muscles are less reactive to serotonin and causes hard or lumpy stools. Those with IBS that have high levels of serotonin can have diarrhea.4
Serotonin Supports Optimal Sleep
Serotonin plays a role in maintaining healthy sleep-wake cycles. Your pineal gland produces the sleep hormone melatonin from serotonin. If you’re low on serotonin, your body will lack the building blocks needed for proper melatonin production. This is why many people suffering from depression experience insomnia as well.5
Serotonin Helps with Blood Clotting
Your body releases serotonin to encourage wound healing. Serotonin triggers the narrowing of arteries, which stimulates blood clotting.
Serotonin Promotes Bone Health
Research suggests that high levels of serotonin may negatively impact bone health. This is associated with people taking medications designed to elevate serotonin levels. These studies reveal that patients who take antidepressants have lower bone density and are more likely to have osteoporosis. 6
What is Serotonin Syndrome?
For optimal health and well-being, you want your serotonin levels just right — not too low or too high. A simple blood test can measure the amount of serotonin in your blood. The normal range for serotonin is 50 to 200 ng/mL.
While low serotonin can lead to many behavioral and mood disorders, high serotonin poses issues as well. When you take medications that increase serotonin action in your body, it can lead to serotonin syndrome. Some of the medications that increase serotonin include:7“
- Analgesics (tramadol, oxycodone, etc.)
- Antidepressants (SSRIs, SNRIs, MAOI inhibitors, tricyclic antidepressants)
- Antiparkensonian agents
- Buspirone (used to treat anxiety)
- OTC cold and cough medicines containing dextromethorphan
Serotonin syndrome can cause many side effects. Common symptoms of serotonin syndrome include:
- Heavy sweating
- Brain fog
- Mild headaches
- High blood pressure
- Muscle twitches
- Diarrhea and nausea
Signs of Low Serotonin
If you experience depression or anxiety regularly, you likely have low serotonin levels. Here are common signs you have low serotonin levels:
- Changes in sleep (too little or too much)
- Chronic pain
- Memory loss or dementia
- Little or no appetite
- Cuts that do not heal quickly
- Unable to focus
If you feel you have low serotonin levels, ask your functional medicine doctor to order a serotonin blood test. Now that you understand serotonin’s role in your body and the signs you have too much or too little, let’s talk about how you can boost your serotonin levels naturally.
How to Naturally Boost Serotonin Levels
Conventional medicine uses antidepressants to boost serotonin. However, as I mentioned, these medications have harmful side effects such as dizziness, insomnia, constipation, and increased feelings of anxiety.8 They are also very difficult to stop taking and can cause really awful withdrawal symptoms.9
The good news is that you can boost your serotonin levels without the use of medications through diet and lifestyle changes. Here are four ways you can naturally boost serotonin levels:
Eat More Tryptophan-Rich Foods
You cannot get serotonin directly from food, however foods rich in tryptophan can boost your serotonin production. It’s a misconception that tryptophan itself makes you sleepy. Instead, tryptophan plays a role in the production of serotonin, a mood neurotransmitter that relaxes you. It also supports the natural production of melatonin. Because it’s an amino acid, your body can only get it from your diet.
Foods rich in tryptophan include chicken, turkey, fish, and fruits such as bananas, apples and prunes. Milk is also high in tryptophan and some people drink warm milk before bed to help them sleep. However, dairy is an inflammatory food that causes problems for a lot of people. Dairy foods contain lactose, casein, and whey. Casein is a protein very similar to gluten. Most people that are sensitive to gluten are also sensitive to casein. I recommend everyone eliminate dairy from their diets.
Get More Exercise
As the saying goes, exercise releases endorphins, and endorphins make you happy. However, exercise also increases your body’s ability to produce serotonin. While exercise itself does not directly activate serotonin production, it does boost serotonin production indirectly.
When you exercise, your gut-brain axis communicates for your body to release tryptophan into your bloodstream and decrease the amount of other amino acids. This makes it easier for this tryptophan to reach the brain and put you in a better mood.
Aerobic exercise such as swimming, riding a bike, brisk walking, jogging, or hiking increases tryptophan levels in your bloodstream. I love taking walks with my family on a cool fall evening.
Spend More Time in the Sun
One of the main root causes of seasonal depression, or seasonal affective disorder (SAD), is the overproduction of melatonin. Remember, your body produces melatonin from serotonin. Your pineal gland in your brain in response to darkness.
As it gets darker earlier, your body signals it’s time to release melatonin into your bloodstream.10
With longer periods of darkness in the winter months, your body uses more serotonin to make melatonin. This is why you may feel more depressed in the winter than in the summer. Spending 10 to 15 minutes outside every day, especially when the sun is shining, has been shown to increase serotonin levels.11
Gut Bacteria and Serotonin
Your gut is home to the bacteria that helps it produce serotonin. Studies have found that several species of gut bacteria are missing in people with depression, and that imbalances in gut flora can lead to mood imbalances.12
This is why I recommend everyone take a probiotic to ensure a healthy balance of the good bacteria in their gut. In fact, probiotics are one of the four essential supplements that I recommend everyone take every day.
However, not all probiotics are created equal. Probiotic strength is measured in colony-forming units (CFUs). The CFU tells you how much bacteria is present in that probiotic. Unfortunately, many probiotics have a short shelf-life and require refrigeration, as CFUs can die off quickly.
That’s why I formulated Probiotic 30 Billion and Probiotic 100 Billion to include 14 of the most important strains, and made absolutely sure that there were enough viable CFU’s in each capsule to support digestive health and immune function for those looking for the perfect level of daily probiotic maintenance.
Probiotic 30 Billion are designed for daily maintenance, while Probiotic 100 Billion is ideal for rebalancing gut bacteria. However, a soil-based probiotic supplement is best for people with SIBO. A majority of probiotics contain lactobacillus or bifidobacterium, so using a regular probiotic increases the bacteria in your small intestine and adds fuel to the fire. That’s why I recommend soil-based probiotics to anyone with SIBO. Primal Earth Probiotics contain a seed-like structure that survives digestion intact, allowing it to make it to your gut safely!
Gut serotonin is crucial for balancing your mood and supporting healthy digestion. Taking a probiotic with 30 billion or 100 billion CFUs, getting regular sunshine and exercise, and eating plenty of tryptophan-rich foods are all powerful ways to boost your serotonin levels and support your gut health.
- The enteric nervous system and gastrointestinal innervation: integrated local and central control. John B Furness. Advances In Experimental Medicine and Biology, vol. 817. 2014.
- Neurotransmitter modulation by the gut microbiota. Philip Strandwitza. Brain Research. 2019.
- That Gut Feeling. Dr. Siri Carpenter. American Psychological Association. 2012.
- Rationale for using serotonergic agents to treat irritable bowel syndrome. Danial E Baker. AJHP: Official Journal of the American Society of Health-System Pharmacists vol. 62. 2005.
- Insomnia, Serotonin and Depression. Sh V Vashadze. Georgian Medical News. 2007.
- SSRIs: bad to the bone?. Randy A Sansone. Innovations in Clinical Neuroscience, vol. 9. 2012.
- Serotonin Syndrome. Jacqueline Volpi-Abadie, MD.
- Antidepressants: Get tips to cope with side effects. Mayo Clinic. 2019.
- Going off antidepressants. Harvard Health Publishing. 2020.
- Melatonin and Sleep. Eric Suni. Sleep Foundation. 2020.
- Sunshine, Serotonin, and Skin: A Partial Explanation for Seasonal Patterns in Psychopathology?. Randy A. Sansone, MD. Innovations in Clinical Neuroscience. 2013.
- Evidence mounts that gut bacteria can influence mood, prevent depression. Elizabeth Pennisi. Science. 2019.
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