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Low Serotonin Symptoms

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Serotonin is an important neurotransmitter in the central nervous system as well as the circulatory and cardiovascular systems. What does it do? Why is it important? What happens when its levels fall off? How can serotonin levels be increased? Read on to find answers to these questions and more.

Serotonin is a monoamine neurotransmitter synthesized from the amino acid, tryptophan.

Most of the serotonin produced in the body is found in the enterochromaffin cells of the gastrointestinal tract. In the gut, serotonin is chiefly responsible for regulating intestinal movement.

The excess serotonin secreted by the enterochromaffin cells is removed by the veins draining the gut. They are then bound to platelets where they are stored.

The rest of the serotonin present in the body is synthesized in the serotonergic neurons found in the central nervous system where it acts as a neurotransmitter. In the CNS, serotonin contributes to the regulation of sleep, appetite, and mood. It is also involved in memory and learning.

While serotonin acts as a neurotransmitter in the CNS, it acts as a vasoconstrictor in the blood. It is also a growth factor that promotes healing and can also control the release of insulin-like growth factor. Furthermore, serotonin coordinates hormones such as insulin.

Serotonin levels in the body can be affected by a number of factors including diet and drugs.

For example, diets rich in carbohydrate and low in proteins increase serotonin production through insulin. Likewise, foods that contain a much higher amount of tryptophan than competing amino acids such as leucine and phenylalanine promote the production of serotonin.

Therefore, while papaya, banana, and dates improve serotonin production, whole wheat and rye bread reduce it.

In addition, some drugs directly trigger the release of serotonin. This includes tryptophan amino acid supplements as well as levodopa, codeine, and recreational drugs such as cocaine.

Health Effects of Serotonin

Serotonin Receptors

Before discussing the health effects of serotonin in the body, it is important to know about serotonin receptors to which serotonin and drugs that mimic it bind to produce all their effects.

There are 7 serotonin receptors named from 5-HT1 to 5-HT7. Each of these receptors has a number of subtypes.

All serotonin receptors are structurally similar and possess similar mechanisms of action except for 5-HT3.

While the other 6 serotonin receptors are G protein-coupled receptors, 5-HT3 is a ligand-gated sodium/potassium ion channel. Therefore, while the rest serotonin receptors work by reducing or increasing the levels of cAMP (cyclic adenosine triphosphate) inside cells, 5-HT3 works by controlling the transport of sodium and potassium ions across ion channels.

Serotonin receptors are also required for controlling the levels and actions of other neurotransmitters such as epinephrine, norepinephrine, dopamine, acetylcholine, glutamate, and GABA. Therefore, these receptors can produce either excitatory or inhibitory responses in the central nervous system.

Besides neurotransmitters, serotonin receptors also control the release of hormones such as cortisol, prolactin, oxytocin, vasopressin and substance P.

What Serotonin Does

Serotonin is an important neurotransmitter in the brain. It affects most of the cells in the brain either directly or indirectly and because it is able to affect the levels of other neurotransmitters, it produces complex interactions in the brain.

Serotonin exerts its major effects on the parts of the brain responsible for controlling mood, appetite, sexual desire and performance, sleep, memory, learning, social interactions, and temperature regulation.

However, outside the brain, serotonin also affects the cardiovascular system, the endocrine system, and muscles. It has even been found to contribute to the regulation of milk production in the breast.

Serotonin decreases appetite by blocking the actions of dopamine.

Dopamine is responsible for increasing appetite and it is increasingly secreted in the brain when we smell food. But while eating, serotonin production steadily increases and it binds to 5-HT2C receptors found on the cells that produce dopamine. Therefore, serotonin shuts off dopamine production and appetite along with it.

There are instances where serotonin directly acts as a growth factor in the body. For example, the production of both 5-HT2A and 5-HT2B is increased when the liver is damaged. The increased binding of serotonin to these receptors then cause the needed cellular growth to repair the liver.

Serotonin also has an effect on bone metabolism. In fact, it is known to both promote bone loss (5-HT1B) and increased bone mass (through 5-HT2B).

In the cardiovascular system, serotonin acts as a vasoconstrictor which helps stop bleeding. It also acts a growth factor to promote the regeneration of new tissues for healing.

Causes of Low Serotonin Levels

Although the symptoms of low serotonin can be caused by other factors, the major cause is still low levels of serotonin in the brain.

Besides low levels of serotonin, some of the other factors that may trigger these symptoms are:

  • Shortage of receptor sites for serotonin to bind to
  • The inability of platelets to bind and transport serotonin to those receptors

Low serotonin levels can be caused by any of the following factors:

Inadequate Intake of L-tryptophan from Dietary Sources

L-tryptophan is the amino acid used in the production of serotonin. It is capable of crossing the blood-brain barrier.

When foods rich in L-tryptophan are withdrawn from the diet, serotonin production drops and when they are reintroduced, serotonin is increasingly synthesized.

Foods rich in L-tryptophan include meat, poultry, nuts, and dairy products.

Vitamin B6 Deficiency

Vitamin B6 or pyridoxal 5-phosphate is an essential coenzyme in the synthesis of serotonin from L-tryptophan. Therefore, it is also required for optimal production of serotonin.

People who experience vitamin B6 deficiency often have low serotonin levels too.

Competing Amino Acids

It sounds like the right thing to advise that proteins should be taken to increase serotonin production. However, diets high in proteins usually lead to low levels of serotonin chiefly because of the number of amino acids competing for absorption.

Therefore, the usual advice is to adopt low-protein and high-carbohydrate diets.

High-protein foods flood the body with amino acids that compete to cross the blood-brain barrier. This means that the amount of tryptophan crossing into the brain is reduced, and therefore, serotonin production is reduced.

The amino acids that most compete with tryptophan are those that are structurally similar especially the branched chain amino acids such as valine, leucine, and isoleucine.

On the other hand, foods rich in carbohydrate increase insulin levels which drives the absorption of most of these amino acids (except tryptophan) into the cells outside the brain especially muscle cells. Therefore, the concentration of tryptophan in the blood is high enough for a significant amount to cross over into the brain.

Non-essential amino acids such as theanine found mostly in the leaves of green tea may also directly reduce serotonin levels in the brain.

Theanine can cross the blood-brain barrier and compete against tryptophan. It not only reduces the amount of tryptophan to be used for synthesizing serotonin but also degrades serotonin and block its release from nerve endings.

Symptoms of Low Serotonin Levels

Because serotonin has a profound effect on the central nervous system and also on the cardiovascular and musculoskeletal systems, low levels of serotonin can cause some very serious effects.

The symptoms of low serotonin levels can be classified under two headings: physical and emotional.

Physical Symptoms of Low Serotonin Levels

  • Chronic, persistent fatigue – this happens even though the sufferer is fully rested and is inactive most of the time
  • Sleep Disorders – although quick to fall asleep, the sufferer has trouble sleeping soundly due to anxiety and even restless leg syndrome
  • Loss of appetite and craving for carbohydrate – the sufferer may lose interest even in eating but also crave carbohydrates as the body tries to restart serotonin production by causing spikes in insulin production. This may lead to weight gain
  • Hot flushes and fluctuating body temperature – these are caused by the interplay of neurotransmitters trying to compensate for serotonin at serotonin receptors especially in the hypothalamus
  • A migraine and headaches – these are caused by metabolic disorders caused by low serotonin levels
  • Gastrointestinal pain – this is caused by the reduced gastrointestinal movement caused by low secretion of serotonin by enterochromaffin cells in the gut

Emotional Symptoms of Low Serotonin Levels

  • Emotional numbness and social withdrawal – sufferers lose interest in social engagements and experience dour moods
  • Depression – this is the classic sign of low serotonin levels and the reason drugs such as SSRIs that increase serotonin levels are used as antidepressants
  • Increased emotional sensitivity – this can present as low self-confidence, low self-esteem, and low threshold to taking offense. This leads to sudden crying spells and bouts of sadness
  • Loss of interest in sexual activities and irritability
  • Obsessive-compulsive disorder

Treating Low Serotonin

There are different ways to boost serotonin levels. Some of these are described below:

Exercise and Meditate

Different studies have found that moderate exercise is enough to improve mood and increase serotonin levels. Similarly, all forms of meditation may help overcome anxiety and overcome any emotional difficulties that cause depression.

Spend some Time Outside in the Sun

Natural light especially sunlight helps reduce the levels of melatonin which competes with serotonin. The release of serotonin in certain parts of the brain (and even the expression of some serotonin receptors) follow diurnal rhythms.

Therefore, the production of serotonin is at its peak in the morning and it is helped by spending time exposed to natural light

Eat Carbohydrate-rich Foods and Proteins Rich in Tryptophan

Carbohydrate-rich food helps recruit insulin which drives the synthesis of serotonin by encouraging more tryptophan to cross into the brain.

However, too much carbohydrate may cause rapid weight gain. To prevent this, carbohydrates with low glycemic indices are recommended. This includes barley, oats, and buckwheat.

In addition, proteins that serve as a dietary source of tryptophan are also recommended to help increase serotonin levels. Such proteins include poultry, meat, dairy foods, soy, and legumes.

Take Serotonin Supplements

Supplements can also be taken to help improve serotonin levels. The most important of these is tryptophan supplements.

A tryptophan supplement can help increase serotonin levels by increase plasma concentration of tryptophan which then increases the amount of the amino acid that crosses over to the brain.

Alternatively, serotonin supplements can also be used. It directly supplied serotonin to the body. A good example of such supplements is Seronex.

Herbs that increase serotonin production are also effective. These include St. John’s wort and Panax ginseng. However, care should be taken not to take these supplements with serotonergic drugs as the combination may cause a toxicity reaction referred to as serotonin syndrome.

Take Serotonin Medications

Drugs that increase serotonin levels in the brain can also be used to treat low serotonin symptoms.

The major classes of drugs used are SSRIs (selective serotonin reuptake inhibitors) and SNRIs (serotonin-norepinephrine reuptake inhibitors) which are also antidepressants. These drugs allow serotonin to act longer at nerve endings by preventing their reabsorption.





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