Is There a Link Between Bile Acids, the Microbiome, and Mental Health?
- Sophie Nielsen
- May 6
- 4 min read
We often think of bile as simply a digestive fluid, something that helps break down fats after a meal. But emerging research is revealing a much broader role. Bile acids are not just digestive helpers; they are powerful signalling molecules that interact with the gut microbiome, influence inflammation, and may even shape brain function.
So, could bile acids play a role in mental health and neurodiversity? Let’s explore how digestion, microbes, and the brain are more connected than we once thought.
Bile, the Microbiome, and the Brain
Bile acids are produced by the liver and stored in the gallbladder, ready to be released into the small intestine. Beyond fat digestion, they act as chemical messengers that help regulate the gut environment.
One of their key roles is maintaining balance in the gut microbiome. Certain beneficial bacteria depend on bile acids, while others are kept in check by them. This balance is critical because the gut and brain are in constant communication through what’s known as the gut-brain axis.
When bile flow is impaired, whether due to sluggish secretion, altered composition, or stagnation, it can trigger a ripple effect:
The microbiome may shift toward dysbiosis (an imbalance of bacteria)
Harmful microbes may proliferate while beneficial ones decline
Microbial signalling to the brain may be alteredThis disruption doesn’t stay confined to digestion; it can influence inflammation, metabolism, and even neural signalling.
Bile as a Microbial Modulator
Bile acids help shape not only which microbes live in the gut, but also what they produce.
When bile flow is optimal:
Beneficial bacteria produce short-chain fatty acids (SCFAs), which support brain health and reduce inflammation
Primary bile acids are converted into secondary bile acids, which act as signalling molecules throughout the body
When bile flow is disrupted:
SCFA production may decrease
Microbial diversity may decline
The balance of bile acid signalling may shift
These changes can influence the gut environment in ways that extend far beyond digestion.
Neurotransmitters and Gut Signalling
One of the most fascinating aspects of the gut-brain connection is that many neurotransmitters are influenced, or even produced, by gut microbes. For example:
Around 90% of the body’s serotonin (often called our “happy hormone”) is produced in the gut
GABA, a calming neurotransmitter, is also influenced by microbial activity
Changes in bile formation or flow can indirectly affect these systems by reshaping the microbiome. This may:
Alter which bacteria are present and active
Influence neurotransmitter production and balance
Affect how signals are transmitted along the gut-brain axis
Additionally, bile acids themselves interact with receptors in the enteric nervous system (sometimes called the “second brain”), further influencing communication between the gut and the central nervous system.
Emerging Links to Mental Health
Several studies are beginning to explore connections between bile dysregulation, dysbiosis, and neurological or psychological outcomes:
Mood and anxiety: Chronic low-grade inflammation originating in the gut is linked to depression and anxiety. Bile acids help regulate this inflammation, so poor bile flow may indirectly contribute to mood disorders
Cognitive function: Bile acids influence metabolic signalling and detoxification, which could affect brain health over time
Impaired bile flow may impact cognitive clarity and energy levels.
Neurodiversity: Altered bile acid profiles have been observed in some individuals on the autism spectrum and in other neurodevelopmental conditions, highlighting a potential link between bile acids, the gut microbiome, and neural function
Why This Matters
Understanding bile as more than a digestive fluid supports the role of the gut-brain axis in shaping mental health. Poor bile flow isn’t just associated with symptoms like bloating or reflux. It may also:
Influence systemic inflammation
Affect neurotransmitter balance
Disrupt the gut-brain dialogue
Impair absorption of essential fatty acids like omega-3s, which are crucial for brain structure and mood regulation.
A Complex, Interconnected Picture
It’s important to keep perspective: bile flow is unlikely to be a single “cause” of mental health conditions. Instead, it may be one piece of a much larger puzzle that includes factors such as genetics, diet and lifestyle, your microbiome composition and even environmental factors.
What this emerging research highlights is something more fundamental: mental health is not shaped by the brain alone. It is the product of constant communication between systems - digestive, microbial, immune, and neurological.
Bile plays an important role beyond digestion, forming part of a complex gut–brain network. Through its effects on the microbiome, inflammatory pathways, and neurotransmitter signalling, bile flow may subtly shape how we feel, think, and function.
If you’re experiencing symptoms linked to poor bile flow, supporting gut health, including bile function, may be one piece of the puzzle for your overall mental and neurological wellbeing.
References:
Kumar et al. 2023. Pharmaceuticals (Basel). PMID: 37111321.
Morys J, Małecki A, Nowacka-Chmielewska M. 2024. Front Mol Neurosci. PMID: 39092201.
Wang H, Chen J. 2023Frontiers in Neuroscience. PMID: 39566821.
Bu et al. 2026. Front Cell Infect Microbiol. PMID: 41561085.(5) Golubeva et al. 2017. EBioMedicine. PMID: 28965876.
If you have been struggling with your digestion and mental health, and are tired of band-aid or quick fix approaches, then book a call with Sophie and find out how a functional medicine approach can finally address, and improve, your mental and physical wellbeing once and for all.
