Serotonin, also called the happy hormone, is a versatile neurotransmitter that benefits our body.

Serotonin: Definition And 7 Functions Of This Neurotransmitter

Discover 7 functions of this neurotransmitter and how to naturally increase serotonin levels

Serotonin, also called the happy hormone, is a versatile neurotransmitter that benefits our body. Serotonin is a versatile neurotransmitter that benefits our body.

Our mood depends largely on the external successes we experience but it is also regulated by a series of chemicals in our bodies. Any imbalance of these chemicals, either too little or too much of them will most likely cause mood swings. 

One of the most popular hormones associated with effects on our state of mind is serotonin. We will examine the definition of serotonin, what its functions are, what happens when serotonin levels drop, and how to increase them naturally. 

What is serotonin?

Serotonin is a chemical that occurs naturally in our bodies and although it holds many important roles it is mostly known for its contribution to improving our mood. This is why serotonin is also called the "happy hormone". 

The neurotransmitter serotonin is synthesized from the dietary amino acid tryptophan, which means that a higher level of tryptophan will result in more serotonin. We can increase the amount of tryptophan in our bodies by including food such as nuts, cheese, and red meat in our diet. 

Although not the only cause, a tryptophan deficiency may cause low levels of serotonin which is associated with mood swings, anxiety, and depression.

Aside from the support it offers to our emotional balance, our nervous system uses serotonin to pass messages between nerve cells. According to research, this activates the contraction of smooth muscles and considering serotonin is a precursor to melatonin, it helps regulate sleep-wake cycles. 

Other functions of the neurotransmitter are closely related to the appetite, and motor, cognitive, and autonomous functions. Nevertheless, scientists still need to conclusively determine if serotonin has a direct effect on our bodies or more of a general role in regulating the nervous system. 

7 Functions of this neurotransmitter 

As a neurotransmitter, serotonin is responsible for enabling neurotransmission via neurons or simply put, serotonin is a chemical messenger which transmits signals across a chemical path. 

Despite an ever-increasing number of functions attributed to serotonin, one of its primary functions is in our central nervous system (CNS), as well as the general functioning of our bodies, especially our intestinal tract.

Moreover, some studies suggest that there is a strong connection between serotonin and bone metabolism  (or bone remodeling), the production of breast milk, liver regeneration and cell division.  

This is how serotonin acts in various ways across the human body:

1. Mood enhancer

The serotonin flowing through our brains is  responsible for affecting our mood, anxiety levels, and happiness. 

Some of the most popular illicit drugs, such as extasy and LSD, are known to significantly increase the level of this neurotransmitter. 

2. Intestinal function

Although it may sound unusual because it's mostly associated with the brain,  most of the serotonin that flows through our bodies is focused in our intestinal tract. 

This is where the intestinal functions are regulated as well as the bowel movements. Furthermore, serotonin is responsible for the feeling of satiety and reducing the appetite while eating. 

3. Sexual function

According to some scientists, serotonin appears to inhibit sexual activity. This hypothesis is related to the effects of antidepressants. 

It has been observed that selective serotonin reuptake inhibitors (SSRIs) increase the levels of serotonin in persons with depression but in a majority of cases (20-70%), patients experienced cases of sexual dysfunction. 

4. Bone density

Although there are many contradicting results and opinions, some studies have concluded that  a high level of serotonin in our bones might increase the risk of osteoporosis.  

5. Helps blood coagulation

Another function of serotonin is connected to blood coagulation, also known as clotting. 

Once we have experienced a wound, serotonin is released into the body facilitating the constriction of blood vessels, reducing the blood flow and forming blood clots. 

6. Nausea 

When we ingest expired food or a substance that the body identifies as toxic, the gut produces more serotonin to increase transit time and expel the irritant in diarrhea. 

Moreover, this increase in the levels of serotonin stimulates the area of the brain responsible for nausea, resulting in nausea which again, helps expel the irritant through vomiting. 

The functions of serotonin include the production of melatonin and regulating our sleep cycle.
One of the functions of serotonin is connected to the production of melatonin and our sleep cycle.

7. Regulates sleep

As mentioned previously, serotonin is a precursor of melanin - a hormone known as the "sleep hormone" - produced in the pineal gland which regulates wakefulness. 

Melatonin's main function in the body is to regulate sleep-wake cycles. Darkness causes the body to produce more melatonin, which signals the body to prepare for sleep. Light reduces melatonin production and signals the body to prepare for being awake.

This means that, in many cases, people struggling to sleep suffer from an imbalance in their levels of serotonin, which affects the production of melatonin and impacts the normal running of night and day cycles. 

Low serotonin levels: Depression and other symptoms

As we have discovered, serotonin is a neurotransmitter that helps regulate and elevate our state of mind, which is why a serotonin deficit may cause emotional imbalances such as depression and other psychological or cognitive variations. 

The exact causes of depression are unknown, but some of the theories suggest that a chemical imbalance in our bodies, such as issues with hormones, could be a potential reason. 

Depression has been linked to low serotonin levels but scientists haven't concluded if the dip in serotonin causes the depression, or the depression causes serotonin levels to drop.

These are the main symptoms associated with low levels of serotonin. 

  • Memory loss

  • Low mood

  • Low self esteem

  • Difficulty sleeping

  • Anxiety

  • Aggression

The amino acid tryptophan is responsible for increasing the levels of serotonin.
Dairy, bananas, and dry fruit can boost the levels of serotonin via the amino acid tryptophan.

How to naturally increase serotonin levels?

Prescription drugs and illicit drugs can both increase the level of serotonin in our bodies. While the former are reserved strictly for people who have been diagnosed with mood disorders, the latter have far too many side effects and are highly addictive. 

Luckily,  there are natural ways of increasing our serotonin levels which are much more sensible and beneficial. 

  • Therapy: Psychotherapy and cognitive-behavioral therapies can increase the level of this neurotransmitter and improve a person's state of mind. 

  • Sunshine: Research shows a clear relationship between being exposed to bright light and serotonin levels. To get better sleep, or to boost your mood, try to make time for a daily lunchtime walk outside.

  • Exercise: Physical activity and exercising have an antidepressant effect, and research indicate it could increase serotonin's brain function. 

  • Diet: A healthy diet rich in foods containing tryptophan has been connected to a better state of mind, and better cognitive functioning due to increased levels of serotonin.

Foods that might help increase serotonin levels due to being high in tryptophan: 

  • Food rich in protein  (turkey, eggs, and cheese)

  • Bananas

  • Pineapple

  • Avocado

  • Plums

  • Spinach

  • Dry fruit

  • Seeds

  • Legumes

  • Brewer's yeast

  • Soy products

  • Salmon

  • Spirulina

Your best chance at achieving a serotonin boost without using supplements is to eat them often, with a serving of healthy carbohydrates, like rice, oatmeal, or whole-grain bread.



Cowen, P. J. & Browning, M. (2015). What has serotonin to do with depression?. World Psychiatry, 14(2): 158–160.

Feldman, J. M. & Lee, E. M. (1985). Serotonin content of foods: effect on urinary excretion of 5-hydroxyindoleacetic acid. The American Journal of Clinical Nutrition, 42(4): 639–643.

Young, S. N. (2007). How to increase serotonin in the human brain without drugs. Journal of Psychiatry & Neuroscience, 32(6): 394–399.