Over the past decade, scientists have begun exploring a new field sometimes called metabolic psychiatry.
This emerging area of research suggests that some mood disorders may be linked not only to neurotransmitters, but also to how brain cells produce and use energy.
The brain is one of the most energy-demanding organs in the body. Although it represents only about 2% of body weight, it consumes roughly 20% of the body’s energy supply.
Every thought, memory and emotional response depends on tiny cellular structures called mitochondria, which produce energy within our cells.
When mitochondrial function becomes impaired, brain cells may struggle to regulate signalling, inflammation and stress responses.
Researchers are now studying how metabolic dysfunction, inflammation and cellular energy production may influence conditions such as depression, fatigue, cognitive dysfunction and neurodegenerative disease.
The vagus nerve connection
Another important piece of this puzzle is the vagus nerve, the longest cranial nerve in the body.
The vagus nerve is one of the main pathways of communication between the brain and the digestive system. It carries signals between the brainstem and organs, including the stomach, intestines, liver and heart.
Remarkably, most of these signals travel from the body to the brain, meaning the brain is constantly receiving information about digestion, inflammation, nutrient status and microbial activity.
Through this signalling pathway, the gut can influence brain chemistry, stress responses and emotional regulation.
This is one reason the gut–brain axis has become such an important area of research in modern neuroscience.
Energy, inflammation and brain signalling
Inflammation, mitochondrial energy production and neural signalling are deeply interconnected.
When chronic inflammation occurs in the body, it can disrupt mitochondrial function and increase oxidative stress. This may impair how brain cells produce energy and communicate with one another.
Inflammatory signalling may also influence neurotransmitters involved in mood regulation, including serotonin and dopamine.
Researchers are increasingly recognising that mood disorders may involve a combination of factors, including brain circuit dysfunction, inflammation and metabolic imbalance.
Understanding these connections is helping scientists move toward a more integrated view of mental health.
The role of plant compounds
Many medicinal plants contain compounds that support antioxidant defence, regulate inflammatory pathways and influence cellular metabolism.
These actions may help support the biological environment in which healthy brain signalling occurs.
For example:
Rhodiola (Rhodiola rosea) has been studied for its ability to support cellular energy production and resilience to stress.
Turmeric (Curcuma longa) contains curcumin, a compound known to influence inflammatory pathways and support neuronal protection.
Ashwagandha (Withania somnifera) contains withanolides that support stress regulation and may help protect neurons from oxidative stress.
Rosemary (Rosmarinus officinalis) contains antioxidant compounds that support cellular protection within neural tissue.
These plants illustrate how herbal medicine often works by supporting multiple biological systems simultaneously rather than targeting a single pathway.
A systems perspective
Across this series, we have explored how epigenetics, inflammation, gut signalling and brain energy metabolism interact.
These systems do not operate independently.
Gene expression can influence inflammation. Inflammation can affect mitochondrial energy production. Gut microbes can influence immune signalling and neurotransmitter balance.
The vagus nerve acts as one of the major communication highways connecting these systems.
Understanding these interactions highlights an important principle of human biology.
Health emerges from the balance of interconnected systems rather than a single isolated pathway.
Science and tradition meet in the middle
What is particularly exciting today is the growing convergence between modern neuroscience and traditional herbal knowledge.
Advanced research is revealing how inflammation, metabolism, microbial signalling and brain circuits interact to shape mental wellbeing.
At the same time, traditional herbal medicine has long worked with these interconnected systems through digestive support, stress regulation and plant compounds that influence inflammation and cellular resilience.
As research continues to evolve, science and traditional herbal wisdom are increasingly meeting in the same place.
The brain, the gut, the immune system and cellular metabolism are not separate systems.
They are part of one deeply interconnected network that shapes human health.
Research
Metabolic psychiatry and brain energy research
https://pubmed.ncbi.nlm.nih.gov/34671115/
Gut–brain axis signalling
https://pubmed.ncbi.nlm.nih.gov/22498897/
Vagus nerve and brain–gut communication
https://pubmed.ncbi.nlm.nih.gov/25830558/
Curcumin and neuroinflammation
https://pubmed.ncbi.nlm.nih.gov/19303921/