Serotonin: Functions, Normal Range, Benefits, Side Effects - Dr. Axe

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Serotonin: Why You Need It and How to Boost Levels Naturally


Serotonin - Dr. Axe

Do you know that serotonin plays a role in virtually all human behavioral processes? From your emotions to digestion and motor skills, this powerful chemical impacts so many aspects of life and body function.

Serotonin receptors are found throughout the brain, where they work as neurotransmitters that send messages from one area to another, but the majority of serotonin in the human body is actually found in the gut, where it influences a number of biological processes, including digestion, appetite, metabolism, mood and memory.

Increasing your serotonin levels may work as a natural remedy for depression and improve your overall mood, but with this and any neurotransmitter (such as acetylcholine), you don’t want too much of it to accumulate in the body either. That’s why increasing your levels naturally is a better option than using antidepressants with nasty side effects.

What Is Serotonin?

Serotonin is a type of chemical that acts as a neurotransmitter, meaning it helps send signals from one area of the brain to another. The chemical name for serotonin is 5-hydroxytryptamine, and it’s sometimes called 5-HT. As a neurotransmitter, it controls neural activity and plays a role in a wide range of neuropsychological processes.

Only 2 percent of the body’s serotonin is found in the brain, and 95 percent is produced in the intestine, where it modulates hormonal, endocrine, autocrine and paracrine actions. In the brain, it occurs naturally in the body and works as a neurotransmitter, sending chemical messages or signals to the brain in order to regulate motor function, pain perception and appetite.

It also modulates various biological processes, including cardiovascular function, energy balance, digestive function and mood regulation.

It is a byproduct of tryptophan, an essential amino acid that’s known for its ability to regulate mood and balance hormones naturally. Tryptophan converts to serotonin in the brain and helps make other essential amino acids available to help control your mood and reduce your production of stress hormones.

Serotonin vs. Dopamine

What is the function of serotonin and dopamine? Both are neurotransmitters that play a role in depression.

Serotonin functions as a mood regulator, and it also plays a role in many other body processes, like digestion and sleep. Dopamine is connected to what’s called the “pleasure center” in the brain. Your body gets a rush of dopamine when you are rewarded, but low levels of dopamine may lead to low motivation and feelings of helplessness.

The major difference is how the two neurotransmitters affect your mood. Dopamine is released after pleasurable experiences, and it alters your motivation and interest, while serotonin impacts the way you process emotions.

For optimal health, we need to keep both levels in balance.

Another brain chemical that plays some similar roles as serotonin and dopamine is oxytocin, which is primarily associated with feelings of love.

Relation to Mental Health and Depression

Serotonin transmits signals between our nerve cells, giving it the ability to alter brain functions that affect our mood and sleep. Serotonin for depression has been the focus of many clinical and preclinical studies over the years. Researchers know that the chemical signals many receptors throughout the brain regions in humans, but the exact mechanisms of serotonin as an antidepressant are still being explored.

Research conducted at Columbia University indicates that while the majority of the 15 known receptors for serotonin have been linked to depression and depression-like behavior, the 1A and 1B receptors are the most studied. Human brain imaging and genetic studies show that these two receptors are involved in depression and the response to antidepressant treatment.

According to a review published in World Psychiatry, “evidence suggests that impairing serotonin function can cause clinical depression in some circumstances.”

Moreover, evidence suggests that low serotonin function may compromise a patient’s ability to maintain recovery from depression, rather than it having a primary effect on lowering mood in vulnerable people.

This seems to be true because studies show tryptophan deletion is much more apparent in people with prior episodes of depression in comparison to those who are simply at a higher risk of depression because of family history.

Studies involving selective serotonin reuptake inhibitors (SSRIs) indicate that it may not be the neurotransmitter’s’ direct effects on our mood, but rather its ability to promote positive shifts in automatic emotional responses that helps relieve symptoms of depression.

Serotonin Benefits and Uses

1. Improves Mood and Memory

Studies indicate that low brain serotonin levels are associated with poor memory and depressed mood. We also know that serotonin and tryptophan produce alternations in the gut that alter the gut-brain axis and impact your mood and cognitive health.

Researchers have been able to explore the role of serotonin for depression by investigating the effects of lowering dietary tryptophan levels, causing a lowering of brain serotonin levels.

2. Regulates Digestion

Ninety-five percent of the body’s serotonin is produced in the intestine. Research shows that the chemical plays a role in intestinal motility and inflammation.

When 5-HT is naturally released, it binds to specific receptors in order to initiate gut motility. It also regulates appetite, and it produces more of the chemical to help eliminate foods more quickly when they are irritating to the digestive system.

3. Relieves Pain

A study published in the journal Pain Research and Treatment found there is an inverse correlation between postoperative pain levels in patients with chronic low back pain and serum serotonin levels.

Another study found that when healthy volunteers underwent acute tryptophan depletion to manipulate 5-HT function, they experienced a significantly reduced pain threshold and tolerance in response to a heat thermode.

4. Promotes Blood Clotting

We need enough serotonin to promote blood clotting. The chemical is released in blood platelets to help with wound healing. Plus, it works to narrow tiny arteries so they form blood clots.

Although this serotonin benefit helps in the healing process, there’s also evidence that too much serotonin can lead to blood clots that contribute to coronary heart disease, so it’s important to stay within the normal range to prevent adverse effects.

5. Helps Wound Healing

A study published in the International Journal of Molecular Sciences found that serotonin acts as a potential therapeutic candidate for enhancing skin healing in burn patients. Researchers found that serotonin significantly accelerated cell migration and improved the wound-healing process in vitro and vivo models of burn injuries.

Normal Ranges

You can have your serotonin levels tested with a blood test. Blood is typically drawn from the vein and sent to the lab for results.

People who are at risk of serotonin deficiency or carcinoid syndrome (high serotonin levels) may need a blood test. The normal serotonin range is 101–283 nanograms per milliliter (ng/mL).

After receiving your levels from a lab, it’s best to discuss them with your health care provider, as test measurements may differ and change what’s considered a normal result.

Deficiency Symptoms and Causes

Research shows that impaired serotonin function has been associated with psychiatric disorders, including:

Low serotonin symptoms include the following:

  • Depressed mood
  • Anxiety
  • Panic attacks
  • Aggression
  • Irritability
  • Trouble sleeping
  • Appetite changes
  • Chronic pain
  • Poor memory
  • Digestion issues
  • Headaches

What causes low serotonin levels? Serotonin is part of a complex system of chemicals and receptors. If you have low serotonin levels, you may have deficiencies in other neurotransmitters, which is what causes such noticeable symptoms.

Researchers don’t know for sure what causes serotonin deficiency, but it may be due to genetics, poor diet and lifestyle.

If you deal with chronic stress or are exposed to toxic substances, like heavy metals or pesticides, you may be at a greater risk of low serotonin. Other causes may include a lack of sunlight and taking certain medications for a long period of time.

How to Treat Deficiency

There are natural serotonin foods and boosters that can increase levels of serotonin without the need for pharmaceutical drugs.

1. Anti-Inflammatory Foods

Did you know the health of your gut alters your body’s ability to produce serotonin? It’s important you eat anti-inflammatory foods that improve the health of your gut and promote the balance of good and bad bacteria.

Some of the best foods include wild-caught salmon, eggs, leafy greens, nuts and fresh vegetables.

To maximize the good bacteria in the gut, probiotic foods are also beneficial. Eating or drinking kefir, kombucha, probiotic yogurt and apple cider vinegar help improve the health of your gut.

Healthy fats, like avocado, coconut oil, extra-virgin olive oil and ghee, also help reduce inflammation and promote the natural production of serotonin.

2. Exercise

Research shows that exercise has beneficial effects on brain function because it modulates the neurotransmitters dopamine, serotonin and noradrenaline. These chemical messengers contribute to exercise, affecting brain function and even improving neurological disorders.

3. Get Enough Sunlight

The serotonin neurotransmitter is not produced properly if you don’t get enough sunlight. Research suggests that there’s actually a direct relationship between sunlight and the production of serotonin. It’s believed that exposure to sunlight triggers the brain to release the chemical.

This may explain, at least in part, why low levels of serotonin are associated with seasonal affective disorder.

4. Tryptophan

Research published in Nutrients shows that reduced intake of tryptophan can lead to significant reductions in certain brain activities that boost happiness.

According to a study, patients are often successful at lowering negative symptoms related to mood disorders, addictions or hormonal problems when they take six grams of L-tryptophan per day. Taking this amount of tryptophan every day for several months has been shown to decrease mood swings, irritability, tension and restlessness.

5. 5-HTP

5-HTP, or 5-Hydroxytryptophan, is an amino acid that’s naturally produced by the body. It’s used to produce serotonin, which is why 5-HTP supplements are often used to improve mood and reduce symptoms of depression. You can find 5-HTP supplements online and in health food stores.

SSRIs Uses and Side Effects

SSRIs are used to improve symptoms of depression by increasing levels of serotonin in your brain. Some of the most common types of SSRIs include Prozac and Zoloft.

Neuropsychological studies have found that in both healthy and depressed participants, administration of SSRIs led to positive shifts in the way the brain reacted to emotionally driven information. Other studies, however, report different results, suggesting that only 50 percent of patients respond to SSRIs and effective remission occurs less than 30 percent of the time, indicating that new antidepressant strategies are needed.

SSRIs are the most commonly prescribed antidepressant drugs in the world, but they don’t come without potential side effects. Some of the most common side effects include drowsiness, nausea, nervousness, dizziness, headaches, diarrhea, trouble sleeping, sexual problems and blurred vision.

SSRIs also interact with certain medications and can have dangerous effects when combined with some pharmaceutical drugs or herbal supplements. Be sure to consult your health care provider about possible interactions.

There is the risk of experiencing withdrawal-like symptoms after stopping SSRIs as well. These symptoms may include a feeling of uneasiness, dizziness, nausea, flu-like symptoms and more.

In addition to SSRIs, another class of drugs that are used for depression are called serotonin-norepinephrine reuptake inhibitors, or SNRIs. These drugs increase levels of both serotonin and norepinephrine, another neurotransmitter.

Serotonin Syndrome Causes and Treatment

Serotonin syndrome, which is a type of serotonin toxicity, is when high levels of the chemical accumulate in the body. This is sometimes caused by taking two or more medications that raise levels or combining medications with some herbal supplements.

Abuse of illegal drugs, like LSD, cocaine, ecstasy and amphetamines, can also cause this condition.

The most common serotonin syndrome symptoms are anxiety, restlessness, agitation, sweating and confusion. In more serious cases, it can also lead to health issues like muscle twitching, muscle stiffness, irregular heartbeat, high blood pressure, high fever and seizures.

Research also suggests high serotonin levels increase the risk of osteoporosis due to its effects on our bones. If you notice these symptoms, consult your health care provider, and talk to him/her about having your levels tested.

For people dealing with this condition, serotonin syndrome treatment involves withdrawal from the drugs or medications that are causing your chemical levels to be too high. There are also medications that are used to block production of the neurotransmitter, such as Periactin.

Precautions and Drug Interactions

If you are concerned about low or high serotonin levels, consult your health care provider. Before using pills or supplements to correct a deficiency, seek advice from your doctor, especially if you already take medications to avoid interactions.

There is not enough research to support the use of serotonin supplements during pregnancy or while nursing, so be sure to ask your health care provider before using them.

Final Thoughts

  • The serotonin definition is a neurotransmitter that’s produced within the brain and gut. It sends messages to receptors throughout the brain that allow for several body processes. It affects many parts of the body and allows for internal chemical balance.
  • Are dopamine and serotonin the same? No — they are both neurotransmitters that play a role in mood and emotions, but they are different. The serotonin molecule alters our emotional reactions to life events, while dopamine is influenced by pleasurable experiences.
  • Normal serotonin levels make you feel, well, normal, but levels that are too high or too low can cause adverse effects. When your body produces the right amount, you should experience regular sleep, but too much or too little of it can lead to sleep dysfunction.
  • What happens when your levels are too high? Serotonin syndrome, which occurs when too much of the chemical is produced in the body, can lead to anxiety, restlessness, rapid heart rate and high fever.
  • For people with low levels, supplements, usually in the form of tryptophan or 5-HTP, may help improve the deficiency. Research also suggests exercising, getting daily exposure to sunlight and eating a healthy, anti-inflammatory diet help increase levels naturally.

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