5-Hydroxytryptophan (5-HTP) is an amino acid precursor of serotonin with anti-depressant, anti-anxiety, sleep, and weight loss benefits, but with some caveats. Read this post to learn more about the proven health benefits and risks of supplementing with 5-HTP.

What is 5-HTP?

5-hydroxytryptophan (5-HTP) is an amino acid that serves as a precursor for the biosynthesis of serotonin and melatonin in the brain from the amino acid tryptophan.

Currently, depression is thought to caused (at least partially) by having low levels of serotonin in the brain, however, it is still not fully understood as to what exactly causes depression [1, 2].

5-HTP in supplement form is extracted from the plant Griffonia simplicifolia, an African shrub.

Testing Serotonin

It is not possible to measure serotonin levels in a human brain without a brain biopsy. Indirect markers that are good indicators of serotonin levels in the brain are cortisol levels and blood or urinary HIAA levels [34].

Health Benefits of 5-HTP

1) May Help with Depression

Small clinical studies have shown that 5-HTP alleviates depression better than placebo. However, more large-scale and higher quality studies are necessary to confirm the safety and effectiveness of 5-HTP [5].

The antidepressant effects of 5-HTP are comparable to that of some antidepressants [6].

The combined treatment of 5-HTP and SSRIs seem to have strong synergistic effects on serotonin levels in rats and humans. Therefore, some clinicians recommend the use of slow-released 5-HTP in combination with SSRIs. However, additional clinical trials are required to demonstrate the safety and effectiveness of this approach, and combinations of 5-HTP and medications should only be used under medical supervision [7, 8, 9].

In a small clinical trial involving 52 healthy male subjects, 5-HTP and an SSRI enhanced serotonin levels by 35% and 100%, respectively. Together, however, they increased serotonin by 500% [8].

2) Helps with Panic Attacks and Anxiety

In young adults who suffer stress or anxiety from unreciprocated romanticism, 6-weeks of supplementation with 5-HTP decreased anxiety by 3 weeks. The positive results were attributed to the increased BDNF and serotonin levels [10].

People who suffer from chronic panic attacks, due to lower availability of serotonin in the brain, found significant relief after taking 200 mg of 5-HTP [11].

In clinical trials, herbal extracts of 5-HTP were shown to activate GABA receptors or increase GABA levels, promoting a sense of relaxation and decreased anxiety [12].

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3) Helps with Nightmares in Children

Children aged 3 to 10 who suffer from nightmares had a 93.5% reduction after taking 2 mg/kg of 5-HT for a month every night before bed [13].

4) Helps Reduce Appetite, Cravings

Carbohydrates increase serotonin levels in the brain. Supplementing with 5-HTP can mitigate carbohydrate craving and appetite, thus helps with adherence to dietary interventions and weight loss [1415].

In small clinical trials, 5-HTP supplementation in obese women resulted in no mood changes but decreased food intake and caused weight loss [16, 16].

5) Supports Successful Dietary Intervention in Type II Diabetes

In a 2-week-long clinical trial involving 25 overweight diabetic subjects given no dietary restrictions, subjects who received 5-HTP had reduced caloric, carbohydrate, and fat intake compared to placebo. Subjects who received 5-HTP also have reduced body weight, blood sugar, insulin, and HbA1C levels after 2 weeks, possibly due to changes in the diet [17].

6) Helps Improve Sleep Quality

In a person with a genetic mutation that caused serotonin deficiency, it resulted in a lack of a circadian rhythm and overeating. For this person, supplementation with 5-HTP restored a normal circadian rhythm and food intake [18].

Over long periods of supplementation, production of GABA receptors increased, which assisted with natural sleep cycles and the promotion of healthy sleep [19].

A small clinical trial demonstrated that the use of 5-HTP in combination with GABA significantly improved sleep quality in 9 subjects with sleep disorders, in comparison to placebo [20].

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7) PMS

The absence of increased 5-HTP activity in the dorsolateral prefrontal cortex correlates with premenstrual irritability [21].

While it is possible that 5-HTP supplementation may help with premenstrual symptoms, there is currently no clinical study available to support this benefit of 5-HTP.

8) Phenylketonuria

5-HTP relieves neurological symptoms due to phenylketonuria in mice [22].

5-HTP Versus Tryptophan

1) 5-HTP is Readily Made into Serotonin

The amino acid tryptophan is converted to 5-HTP before it is converted to serotonin. TPH1 and TPH2, the enzymes responsible for converting tryptophan to 5-HTP, are the slowest (rate-limiting) enzymes in serotonin production [23].

5-HTP is readily and freely converted to serotonin without biochemical inhibition.

2) 5-HTP Readily Crosses the Blood-Brain Barrier

Tryptophan competes with leucine, valine, tyrosine, and isoleucine to cross the blood-brain barrier [24].

5-HTP, however, does not compete with other amino acids to enter the brain.

5-HTP readily crosses the blood-brain barrier without receptors or channels.

Serotonin does not cross the blood-brain barrier, so serotonin outside of the brain (in the gut, platelets, heart, and liver) stays separate from serotonin in the brain.

5-HTP gets converted into serotonin both inside and outside of the brain.

3) 5-HTP is Only Made Into Serotonin

While tryptophan can be used for protein synthesis and turning into niacin, 5-HTP can only be used for converting into serotonin [25].

4) 5-HTP Bypasses Neurotoxic Tryptophan Metabolites

Tryptophan can be converted into kynurenic acid and quinolinic acid, which are involved in psychiatric disorders such as schizophrenia, anxiety, depression, and ADHD [25].

These conversions happen more in individuals with inflammation, which may be a link between inflammation and psychiatric or neurological disorders [26, 27, 28].

5-HTP is not directly converted into neurotoxic metabolites [29].

Supplementing with 5-HTP


200 mg is safe and beneficial for increasing serotonin levels in the brain, although some studies have shown safety and effectiveness when titrating doses up to 3 grams per day [5]. Higher dosages increase the likelihood of side effects.

In obesity and weight loss intervention studies, up to 900 mg or 8 mg/kg of body weight of 5-HTP was safely used for 2 weeks, although side effects of nausea and vomiting were reported [16, 16].

5-HTP Absorption and Elimination

5-HTP is rapidly absorbed in the upper intestine, with 50% of 5-HTP absorbed in 1.5 hours [30].

Elimination of 5-HTP is also rapid [30].

Due to the rapid pharmacokinetics of 5-HTP, slow-release supplementation of 5-HTP may be more beneficial to maintain serotonin levels in the brain [9].

About 70% of ingested 5-HTP is found in the bloodstream [31].

Patients who take 5-hydroxytryptophan have severely decreased levels of P450 expression, [32].

Risks and Side Effects of 5-HTP Supplementation

1) May Cause Nausea and Vomiting

Since serotonin in the digestive system controls gut movement, all interventions that increase serotonin levels, including 5-HTP supplementation and SSRI antidepressants, can cause nausea, vomiting, and diarrhea.

The most commonly reported side effects of 5-HTP in all clinical trials in humans are nausea and vomiting as the quick surge of serotonin throughout the body is not well tolerated (33, 34).

Slow-released 5-HTP may be better tolerated and less likely to cause side effects [9].

2) May Deplete Dopamine, Norepinephrine, and Epinephrine

Serotonin shares the same conversion (AAAD) and breakdown enzyme (MAO) with other neurotransmitters (dopamine, norepinephrine, and epinephrine).

Long-term supplementation of 5-HTP can cause imbalances of these neurotransmitters. It is therefore recommended that 5-HTP supplementation is supervised by qualified clinicians and balanced with neurotransmitter precursors [35].

In cases where there is too much 5-HTP, it will reduce dopamine synthesis as a result of overwhelming the AAAD enzyme through competitive inhibition, leading to depletion of dopamine, norepinephrine and other neurotransmitters [35].

With increasing doses of 5-HTP, MAO activity increases. When this happens, MAO can then break down dopamine and cause it to decrease [35].

3) Serotonin Syndrome

5-HTP is freely converted to serotonin without biochemical feedback inhibition. When infinitely high amounts of 5-HTP are administered, it is theoretically possible to achieve extremely high levels of serotonin. One limiting factor is the availability of the enzyme L-aromatic amino acid decarboxylase (AAAD), which is an enzyme that converts 5-HTP to serotonin [35].

Serotonin syndrome explains a set of symptoms caused by very high levels of serotonin, which can be very serious and life-threatening [36].

Mild symptoms include shivering, sweating, tremor, restless limbs, and headache. Serious symptoms include hypertension, fever, mania, hallucination, and ataxia [37].

Serotonin syndrome is almost exclusively caused by SSRI and MAOI combinations, causing excessive levels of serotonin in the brain [9].

5-HTP or 5-HTP in combination with SSRI has not been reported to cause serotonin syndrome [9, 38]. But if it’s taken with SSRIs, it might theoretically increase the risk of serotonin syndrome.

4) Eosinophilia-Myalgia Syndrome

Eosinophilia-myalgia syndrome (EMS) is a disease causing severe, disabling, chronic muscle pain, skin symptoms, and other neurotoxic reactions which have affected over 1,500 people and caused at least 38 deaths. The FDA estimated that there are 10 EMS cases associated with 5-HTP worldwide [39].

It seems more likely that it is caused by bacterial contamination in the supplement than tryptophan or 5-HTP itself. No new cases of supplement-related EMS have been reported since 1990 [40].

Other Side Effects

Other rare side effects of 5-HTP include hypomania, lightheadedness, headache, and heart palpitations [41, 38].

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About the Author

Nattha Wannissorn - PHD (MOLECULAR GENETICS) - Writer at Selfhacked

Nattha Wannissorn, PhD

PhD (Molecular Genetics)

Nattha received her Ph.D. in Molecular Genetics from the University of Toronto and her undergraduate degree in Molecular and Computational Biology from the University of Pennsylvania.

Aside from having spent 15 years in biomedical research and health sciences, Nattha is also a registered holistic nutritionist, a certified personal trainer, has a precision nutrition level 1 certification, and is a certified functional diagnostic nutrition practitioner. As a holistic practitioner with a strong science background, Nattha is an advocate of science literacy in health topics and self-experimentation.

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