Mood Swings, Anxiety, and Depression: Could Your Gut Be to Blame?
If you’ve ever had a “gut feeling” that something was off with your mood, you might be onto something more than intuition. Emerging research continues to affirm what functional medicine has known for years: your gut and brain are deeply connected.
So if you’re struggling with mood swings, anxiety, or depression, it may be time to look beyond your brain—and into your gut.
The Gut-Brain Axis: What Is It?
The gut-brain axis is the bidirectional communication system between your gut and central nervous system. This connection involves the nervous system, immune system, hormones, and even your gut microbiome.
In fact, your gut is often called your “second brain”—housing over 500 million neurons and producing more than 90% of your body’s serotonin (your feel-good neurotransmitter). If the gut is inflamed, imbalanced, or not functioning optimally, this can directly impact your mood, focus, resilience to stress, and overall mental health.
How the Gut Produces Neurotransmitters
One of the most fascinating discoveries in gut health research is that your gut isn’t just digesting food—it’s also helping to make your brain chemicals.
The gut microbiome plays a critical role in the synthesis and regulation of key neurotransmitters involved in mood, motivation, and mental clarity:
Serotonin – Often called the “happy hormone,” about 90–95% of serotonin is produced in the gut. It influences mood, sleep, appetite, and even pain sensitivity. Certain gut bacteria help convert the amino acid tryptophan into serotonin.
Dopamine – Important for motivation, focus, and pleasure. Gut microbes can influence dopamine production and signaling.
GABA (Gamma-Aminobutyric Acid) – A calming neurotransmitter that helps manage stress and anxiety. Specific bacterial strains like Lactobacillus and Bifidobacterium can help increase GABA levels.
Acetylcholine – Supports memory and learning. Its production is impacted by both nutrient availability and microbial balance.
When the gut is inflamed, imbalanced, or leaky, these processes can be disrupted—leading to low mood, anxiety, irritability, or brain fog. This is one reason why someone may feel "off" emotionally even if everything else in life seems fine.
Inflammation in the Gut = Inflammation in the Brain
It’s no coincidence that many people experiencing anxiety or depression also struggle with gut symptoms like bloating, food sensitivities, or IBS. One key connection? Inflammation.
When the gut is chronically inflamed—due to poor diet, dysbiosis, infections, leaky gut, or stress—it can trigger low-grade systemic inflammation that reaches the brain. This is often referred to as neuroinflammation, and it's been strongly linked to:
Brain fog
Fatigue
Depression
Mood swings
Poor stress resilience
One pathway is through something called cytokines—chemical messengers that increase during inflammation. High levels of inflammatory cytokines (like IL-6, TNF-α, and CRP) have been found in individuals with depression and anxiety, especially when gut health is compromised.
Another mechanism? A leaky gut allows toxins and bacterial byproducts like lipopolysaccharides (LPS) to enter the bloodstream. LPS is known to cross the blood-brain barrier and stimulate inflammation in the brain—contributing to mood disorders and even neurodegenerative conditions.
If you’re feeling inflamed in your gut, you may also be inflamed in your mind.
Signs Your Gut Might Be Impacting Your Mood
Frequent bloating, constipation, or diarrhea
Brain fog or difficulty concentrating
Feeling “wired but tired”
Increased sensitivity to stress
PMS mood swings
Depression or low motivation despite external support
Anxiety with no clear trigger
Why a Stool Test Can Be a Game-Changer
In functional nutrition, we don’t just chase symptoms—we uncover root causes. And when it comes to mood imbalances, a comprehensive stool test is one of the most powerful tools we can use.
Here’s what a stool test can reveal:
Dysbiosis – an imbalance of beneficial vs. harmful gut bacteria, which can interfere with neurotransmitter production and increase inflammation.
Pathogens or Overgrowths – such as candida, H. pylori, or parasites that contribute to systemic inflammation and gut-brain disruption.
Leaky Gut Markers – increased intestinal permeability may trigger low-grade inflammation that affects mood and immune function.
Digestive Function – if you’re not breaking down food properly, you may be missing key nutrients like B vitamins, zinc, and magnesium—all essential for mental health.
Short Chain Fatty Acids (SCFAs) – these anti-inflammatory compounds produced by good bacteria play a role in brain function and emotional regulation.
Practical Steps to Start Restoring Balance:
Restoring balance to the gut–brain axis begins with supporting both systems at once — your digestive health and your nervous system.
Nourish your microbiome with a variety of fiber-rich, colorful plant foods and fermented options like sauerkraut or kefir to encourage beneficial bacteria that produce calming neurotransmitters.
Reduce highly processed foods and refined sugars, which can inflame the gut and disrupt mood regulation.
Equally important is calming the nervous system — chronic stress directly alters gut motility, increases permeability, and suppresses beneficial microbes. Practices like deep breathing, gentle movement, meditation, or time outdoors can help rebalance this communication loop.
Quality sleep, hydration, and mindful eating round out the foundation for restoring a healthy gut–brain connection — helping you feel clearer, calmer, and more emotionally resilient from the inside out.
The Takeaways
If you’ve been told your mood issues are “just stress” or brushed off as hormonal, it’s time to dig deeper. You deserve answers—and your gut might be holding the key.
Ready to uncover the root of your mood swings or anxiety? Let’s take a look inside—with functional testing and a holistic plan designed just for you. Schedule your FREE strategy call below to see how we can get to the root cause!