Serotonin: Enhancing this Important Neurotransmitter


Approximately 90% of the human body’s total serotonin is located in the Enterochromaffin (EC) cells in the gastrointestinal tract, where it is used to regulate intestinal movements. The remainder is synthesized in serotonergic neurons of the central nervous system, where it has various functions. 1

Serotonin is related to the brain synchrony and is popularly thought to be a contributor to feelings of well-being and happiness.

Serotonin System

Lobe of the BrainOccipital lobes
Brain MeasurementSynchrony (Rest)
Satisfied feelings
Sleep deeply
Think rationally
DeficiencySleep disorders
Eating disorders
Sensory processing
Diettryptophan-rich: turkey; chicken; sausage; avocados; cheese; cottage cheese; ricotta; eggs; granola; oat flakes; luncheon meats; wheat germ; whole milk; yogurt.
Supplementstryptophan; calcium; fish oil; 5-HTP; magnesium; melatonin; passionflower; pyridoxine; SAM-e; St. John’s Wort; zinc.

The average adult human possesses only 5mg to 10mg of serotonin, 90% of which is in the intestine and the rest in blood platelets and the brain. 

As a neurotransmitter, serotonin allows for  allowing numerous functions in the human body including:

  • behavior
  • cardiovascular function
  • control of appetite
  • depression
  • endocrine regulation
  • learning
  • memory
  • mood
  • muscle contraction
  • sleep
  • temperature regulation

The neurons in the brain that release serotonin are found in small dense collections of neurons called Raphe Nuclei.  The Raphe Nuclei are found in the medulla, pons and midbrain which are all located at the top of the spinal cord.  Serotonergic neurons have axons which project to many different parts of the brain, therefore serotonin affects many different behaviors.

Low serotonin levels are believed to be the cause of many cases of mild to severe depression which can lead to symptoms such as:

  • anxiety
  • apathy
  • fatigue
  • fear
  • feelings of worthlessness
  • insomnia

Serotonin is synthesized from the amino acid L-tryptophan by a short metabolic pathway consisting of two enzymes:

  • tryptophan hydroxylase (TPH)
  • amino acid decarboxylase (DDC)

Pyridoxal phosphate is a required cofactor during decarboxylase enzymatic synthesis from 5-hydroxytyortophan to 5-hydroxytyptamine (5-HT) or serotonin.


Figure 1:  Serotonin Bio-pathway

The enzymes and required cofactors for serotonin are listed in the Table below:

Serotonin Required Enzymes and Cofactors

Amino Acid/NeurotransmitterEnzymeCofactor(s)
L-tryptophantryptophan hydroxylase (TPH) Tetrahydrobiopterin (folic acid is the precursor of Tetrahydrobiopterin)
Magnesium and Vitamin B6 enhances the function of tryptophan hydroxylase (TPH)
5-hydroxytyortophanamino acid decarboxylase (DDC) 5-HTP Decarboxylase
pyridoxal phosphate (active form of Vitamin B6)

Serotonin is the neurotransmitter that provides your brain with synchrony which is defined as the brains electricity moving in waves.   There are 4 types of brain waves: 

  • Beta
  • Alpha
  • Theta
  • Delta

Synchrony is achieved when all 4 brains waves are coordinated throughout the day and night.  If this coordination is in balance, then your brain is synchronous with the cycles of life. 

If these brain waves are out of synchrony at night, you will have restless sleep.  If these brain waves are out of synchrony during the day, your mind will wander and you will have less concentration.

Brain Waves

Brain WaveFrequency RateAssociated Feeling
Beta wave12 - 16 cycles per secondAlertness
Alpha wave8 - 12 cycles per secondCreative
Theta wave4 - 8 cycles per secondDrowsy
Delta wave1 - 4 cycles per secongSleep

There are a number of natural substances that are precursors to the synthesis of serotonin as well as natural substances that may enhance the production of serotonin.  These natural substances are listed in the Table below:

Nutraceuticals and Herbs that Enhance Serotonin

CategoryNutraceuticals and HerbsReference
Amino Acids
St. John’s Wort3
Organic Acids
Hydroxycitric Acid (HCA)5
Whey Protein7
Folic Acid8
Vitamin B69

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