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Serotonin - More than just for happiness

Depression, Digestion, Sleep Disorders, Pain | October 10, 2019 | Author: Naturopath

Gastro intestinal, Insomnia, depression, Pain

Serotonin - More than just for happiness

Serotonin (5-hydroxytryptamine; 5-HT) is a chemical often associated with feelings of happiness, but its functions are way broader. Sleep cycles, appetite and digestion are also influenced by serotonin.

Serotonin is a chemical neurotransmitter found naturally in the body. It is made from an essential amino acid called tryptophan, obtained from the diet. 95% of serotonin is manufactured in specialized enteroendocrine cells within the gastrointestinal mucosa, called enterochromaffin (EC) cells. This accounts for all of the circulating serotonin, the other 5% is produced in the brainstem where it transmits signals between nerve cells in the brain.

Serotonin in the Body

Serotonin regulates a wide range of physiologic and pathophysiologic processes in most human organs. It is involved in many activities such as:

Serotonin in the BodySleep. Serotonin helps regulate circadian rhythm. A circadian rhythm is a natural, internal process that regulates the sleep-wake cycle. It repeats approximately every 24 hours. 

Mood regulation. Serotonin is your happy. It is the chemical which gives you the natural “feel good” sense of wellbeing. Low serotonin is associated with depression.

Digestion. Serotonin acts to initiate and modify the major regulatory functions of the gut. This includes an effect on motility, secretion and vasodilation.

It is involved with both pro- and anti-inflammatory signaling in the intestinal mucosa; regulation of insulin secretion; modulating gut motility (bowel function). If you eat something toxic or irritation, it is serotonin which increases movement through the bowel. Feelings of fullness come from serotonin.

Metabolic syndrome (obesity and type 2 diabetes) - Serotonergic pathways in the central nervous system (CNS) are activated in the regulation of food intake, body weight, glucose homeostasis and lipid metabolism.

Wound healing. Platelets in blood release serotonin when injury to tissue occurs. Serotonin causes vasoconstriction of the tiny blood vessels, slowing- down blood flow as part of blood clotting process.

Bone density. Serotonin influences bone metabolism and maintenance by reducing osteoblast proliferation (bone loss) and supports bone formation.

Haematopoiesis – serotonin is considered a key factor in red blood cell formation and survival.

Metabolic homeostasis – maintenance of body functions.

Pain perception – Serotonin has a major link to pain perception - it both potentiates and inhibits pain processing at various levels of the nervous system.

  • Chronic pain such as that experienced by fibromyalgia have been associated with low serotonin levels.

Could your Serotonin be Low?

When serotonin levels are low it can have an affect on sleep, anxiety, mood, self-esteem, memory, appetite and digestion.

Other physiological disorders which may be associated with low serotonin include: eating disorders, post-traumatic stress, social anxiety disorder, obsessive-compulsive disorder and panic disorder.

Digestive symptoms such as Irritable bowel and constipation can be associated with low serotonin levels.

  • The development of IBS is associated with changes in the gut microbiome, intestinal permeability (leaky gut), gut immune function, motility, visceral sensation, brain-gut interactions, and psychosocial status. These symptoms and signs are influenced by serotonin.

Increasing Serotonin Naturally

Increasing Serotonin NaturallyAerobic exercise. Exercise releases tryptophan into the blood circulation and helps reduce other proteins – this helps tryptophan cross the blood-brain barrier. Do exercise which increases your heart rate.

Aging has been associated with an impairment in serotonin transmission and an increased susceptibility to developing depression.

Studies on older adults have shown that aerobic exercise can stimulate serotonin activity in the brain along with elevations in tryptophan availability in blood plasma. 

Sunshine. The rate of serotonin production is directly related to the duration of bright sunlight. Levels have been shown to increase the more sunlight experienced. This is thought to account for seasonal affective disorder (SAD), experienced by many people during colder months of the year. Try for at least 10-15 minutes daily (maybe include a brisk walk, bike ride or other physical exercise for added benefit).

Probiotic/prebiotics. Studies suggest prebiotics and probiotics have a considerable effect on the regulation of serotonin metabolism. Dietary nutrients and microbial by-products (toxins and fungi) influence gut function. Bacteria within the bowel influence serotonin synthesis and release.

The enterochromaffin (EC) cells are sensory cells scattered within the gastrointestinal tract and are capable of digesting information from ingested nutrients, the enteric nervous system and the gut microbiome.

Do activities which make you enjoy

Focus on a Positive outlook

What to Eat

Foods containing tryptophan - The amino acid tryptophan is the precursor to serotonin (needed to make serotonin).

Inclcude salmon, turkey and red meat; nuts and seeds: Cheese and milk; whole grains – wheat, oats, quinoa; pineapple and banana.

Carbohydrates. Tryptophan works better to make serotonin when consumed with a high-carbohydrate diet and avoid including other proteins. Carbohydrates make tryptophan more available to the brain. For example: Combine salmon or turkey with brown rice or quinoa; Cheese and wholegrain bread; Milk and banana.


Vitamin B6, Niacin, vitamin D and magnesium are needed with tryptophan to synthesize serotonin.

Pure tryptophan

SAMe (S-adenosyl-L-methionine) – Do not combine with other serotonin increasing medication. Click Here for further reading

5-HTP. Is very effective in increasing serotonin

St. John’s wort

Probiotics. Your gut-brain axis is called GBA and connects the central nervous system - spinal cord and brain to the gastrointestinal track. Support this connection from gut to brain by introducing probiotic rich- foods in the diet such as kimchee, yoghurt, tempeh, tofu, miso and fermented vegetables. Supplementing with a probiotic can give a more powerful result.

It is important to discuss with your doctor and naturopath before supplementing to avoid possible interactions and over-dose. Serotonin syndrome is a dangerous condition when too much serotonin is available.

Detox. Support the body and help serotonin levels by removing toxic foods and substances from diet and lifestyle. Eat nutritionally, providing carbohydrates, vitamins and mineral and fibre to aid in the body’s elimination process.

Pharmaceutical intervention

In some cases of low serotonin causing depression, anxiety and sleep disorders medication may be prescribed by the doctor. The most commonly prescribed antidepressant drugs are selective reuptake inhibitor – SSRIs.

In summary

Serotonin is a neurotransmitter affecting your mood, sleep and digestion. Increase levels of serotonin with aerobic exercise, sunshine, a nutritious diet containing foods high in tryptophan and carbohydrates, vitamins and minerals.

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The Expanded Biology of Serotonin https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5864293/

Non-conventional features of peripheral serotonin signaling https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5672796/

Intracellular Serotonin Modulates Insulin Secretion from Pancreatic β-Cells by Protein Serotonylation https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2760755/

Adipocytes express a functional system for serotonin synthesis, reuptake and receptor activation. https://www.ncbi.nlm.nih.gov/pubmed/21320265/

The Diverse Metabolic Roles of Peripheral Serotonin https://academic.oup.com/endo/article/158/5/1049/3058742

Serotonin reuptake inhibitors and bone health: A review of clinical studies and plausible mechanisms



Changes in markers of brain serotonin activity in response to chronic exercise in senior men. https://www.ncbi.nlm.nih.gov/pubmed/25126826

Effect of sunlight and season on serotonin turnover in the brain. https://www.ncbi.nlm.nih.gov/pubmed/12480364

Effects of regulating gut microbiota on the serotonin metabolism in the chronic unpredictable mild stress rat model. https://www.ncbi.nlm.nih.gov/pubmed/31323174


Ineffective erythropoiesis with reduced red blood cell survival in serotonin-deficient mice. https://www.ncbi.nlm.nih.gov/pubmed/21788492

The Gut-Brain Axis: The Missing Link in Depression https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4662178/

Serotonin in the Gastrointestinal Tract https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2694720/

Irritable bowel syndrome: a clinical review. https://www.ncbi.nlm.nih.gov/pubmed/25734736

How to increase serotonin in the human brain without drugs https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2077351/

5-HT modulation of pain perception in humans https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5591803/

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