IngredientsPhenylethylamine (PEA) is an organic compound, natural monoamine alkaloid, and trace amine, which acts as a central nervous system stimulant in humans. It is known under several names that are used interchangeably across scientific literature and the supplement industry. These include 2-phenylethylamine, β-phenylethylamine, and phenethylamine. The compound is also referred to by the systematic IUPAC name 2-phenylethane-1-amine and the alternate descriptor benzeneethanamine.
PEA is a member of the so-called trace amines. The expression "trace amine" is used to refer to a group of amines that occur at much lower intra- and extra-cellular concentrations than the chemically and functionally related biogenic amines and neurotransmitters epinephrine, norepinephrine, serotonin, dopamine, and histamine.
Brain levels of endogenous trace amines are several hundred-fold below those for the classical neurotransmitters noradrenaline, dopamine, and serotonin, but their rates of synthesis are equivalent to those of noradrenaline and dopamine and they have a very rapid turnover rate. Endogenous extracellular tissue levels of trace amines measured in the brain are in the low nanomolar range. These low concentrations arise because of their very short half-life.
In mammals, phenethylamine is produced from the amino acid L-phenylalanine by the enzyme aromatic L-amino acid decarboxylase via enzymatic decarboxylation. In addition to its presence in mammals, phenethylamine is found in many other organisms and foods, such as chocolate, especially after microbial fermentation.
PEA is synthesized by fungi and bacteria and can be found in small quantities in certain food products, especially those that have been fermented. Foods that naturally contain this molecule include various plants in the family Leguminosae, which is composed of trees, shrubs, vines, herbs (such as clover), nuts/seeds like almonds, flaxseeds and walnuts, and legumes/beans (such as soybeans, lentils, chickpeas and green peas). Chocolate is considered one of the best dietary sources, and levels increase in cocoa beans when they are fermented and roasted.
Besides a number of other beneficial substances (e.g., antioxidants), chocolate also contains trace amounts of PEA, a result of the thermal processing and fermentation of cocoa. However, in a study that attempted to determine the concentration of PEA in chocolate, the detection limit for PEA was 3 mg/kg of chocolate and the concentration of PEA in the chocolate samples was below this limit.
Aphanizomenon flos-aquae (AFA), a particular strain of blue-green algae, has been found to have many times more PEA than chocolate.
Studies have found that eating chocolate does not lead to an increase in PEA levels in the nervous system, since it is metabolized rapidly before reaching the brain.
Phenethylamine was first isolated and identified by Marceli Nencki in 1876. Subsequently, it was first synthesized by Treat B. Johnson and Herbert H. Guest in 1909.
Trace amines such as p-tyramine and β-phenylethylamine were discovered more than a century ago and are well known sympathomimetics, described as "false transmitters." After Nencki's initial discovery, other scientists identified phenylethylamine, most often in association with rotting or fermenting food. Nencki's protégé, Jules Jeanneret, reproduced his mentor's results and isolated PEA from gelatin. Schulze and Barbieri presented their discovery that bacteria in an oxygen-free environment can chemically transform the amino acid phenylalanine into PEA in 1879. In 1882 and 1883, Gautier and Etard isolated it from decomposing mackerel.
In the mid-20th century, phenethylamine was identified as a trace amine derived from the decarboxylation of phenylalanine by aromatic L-amino acid decarboxylase (AADC), establishing its biochemical relation to catecholamine biosynthesis pathways. Studies in the 1950s and 1960s demonstrated that this enzyme, primarily acting on tyrosine and tryptophan, also produces low yields of phenethylamine in mammalian tissues, positioning it as a minor endogenous amine structurally akin to dopamine and norepinephrine.
During the 1970s and 1980s, research elucidated phenethylamine's metabolism as a preferred substrate for monoamine oxidase B (MAO-B), accounting for its short biological half-life of approximately 30 seconds in human plasma.
No traditional herbal or ethnobotanical use of isolated PEA has been documented in the peer-reviewed literature. As a discrete chemical entity, PEA has no established tradition in any formal system of plant medicine (Ayurveda, Traditional Chinese Medicine, etc.); its investigation has been wholly within the framework of modern biochemistry and pharmacology. Foods containing PEA — notably chocolate and fermented cheeses — have long been consumed across many cultures, but PEA itself was not identified as an active constituent until its 19th-century chemical isolation.
The salt form, phenylethylamine HCl, is the most common phenylethylamine supplement, and phenylethylamine powders and tablets are also sold. Slow-release versions of phenethylamine have been developed, designed to slowly release phenethylamine over time to prolong its effects. They have not been tested in clinical trials.
Phenethylamine is sold as a dietary supplement for purported mood and weight loss-related therapeutic benefits; however, in orally ingested phenethylamine, a significant amount is metabolized in the small intestine by monoamine oxidase B (MAO-B) and then aldehyde dehydrogenase (ALDH), which converts it to phenylacetic acid.
Phenethylamine supplements have not been approved by the FDA for medical use. Supplements generally lack solid clinical research. Regulations set manufacturing standards for them but don't guarantee that they're safe or effective.
In mammals, phenethylamine is produced from the amino acid L-phenylalanine by the enzyme aromatic L-amino acid decarboxylase via enzymatic decarboxylation. The enzyme phenylalanine decarboxylase (EC 4.1.1.53) catalyzes this reaction. This enzyme belongs to the family of lyases, specifically the carboxy-lyases, which cleave carbon-carbon bonds. The systematic name of this enzyme class is L-phenylalanine carboxy-lyase (phenylethylamine-forming). Other names in common use include L-phenylalanine decarboxylase and aromatic L-amino acid decarboxylase. This enzyme participates in phenylalanine metabolism and employs one cofactor, pyridoxal phosphate.
PEA can be synthesized from L-phenylalanine; however, a large proportion of this amino acid is preferentially converted to L-tyrosine. D-phenylalanine is therefore the preferred substrate for increasing the synthesis of PEA — although L-phenylalanine would also have a mild antidepressant effect because of its conversion to L-tyrosine and its partial conversion to PEA.
Phenylethylamines are a group of phenethylamine derivatives which contain PEA as a backbone. These derivative compounds are formed by replacing one or more hydrogen atoms in the core structure. This class of PEA compounds includes amphetamines, empathogens, stimulants, psychedelics, appetite suppressants, bronchodilators, nasal decongestants, and antidepressants.
Unlike its derivatives norepinephrine (noradrenaline) and epinephrine (adrenaline), phenethylamine is inactive as an agonist of the α- and β-adrenergic receptors.
In humans, PEA is metabolized by phenylethanolamine N-methyltransferase (PNMT), monoamine oxidase A (MAO-A), monoamine oxidase B (MAO-B), the semicarbazide-sensitive amine oxidases (SSAOs) AOC2 and AOC3, flavin-containing monooxygenase 3 (FMO3), and aralkylamine N-acetyltransferase (AANAT).
β-Phenylacetic acid is the primary urinary metabolite of phenylethylamine and is produced via monoamine oxidase metabolism and subsequent aldehyde dehydrogenase metabolism. Phenylacetaldehyde is the intermediate product which is produced by monoamine oxidase and then further metabolized into β-phenylacetic acid by aldehyde dehydrogenase.
Degradation occurs primarily via monoamine oxidase (MAO)-A and -B, with 2-phenylethylamine still the only known endogenous compound showing high selectivity for MAO-B. Trace amines have a remarkable turn-over rate, the half-life for the endogenous pool being less than 30 seconds. Such a high turn-over suggests that trace amines are not stored, consistent with previous reports of a lack of vesicular storage.
When the initial phenylethylamine concentration in the brain is low, brain levels can be increased 1000-fold when taking a monoamine oxidase inhibitor (MAOI), particularly a MAO-B inhibitor, and by 3–4 times when the initial concentration is high.
In addition to the "classical" biogenic amines, other biogenic amines present at much lower concentrations in the CNS and hence referred to as "trace" amines are now recognized to play significant neurophysiological and behavioral functions. At the turn of the century, the discovery of the trace amine-associated receptor 1 (TAAR1), a phylogenetically conserved G protein-coupled receptor that is responsive to both trace amines such as β-phenylethylamine, octopamine, and tyramine, and structurally related amphetamines, unveiled mechanisms of action for TAs other than interference with aminergic pathways.
Although its molecular interactions and downstream targets have not been fully elucidated, TAAR1 activation triggers accumulation of intracellular cAMP, modulates PKA and PKC signaling and interferes with the β-arrestin2-dependent pathway via G protein-independent mechanisms. TAAR1 is uniquely positioned to exert direct control over DA and 5-HT neuronal firing and release, which has profound implications for understanding the pathophysiology of, and therefore designing more efficacious therapeutic interventions for, a range of neuropsychiatric disorders that involve aminergic dysregulation, including Parkinson's disease, schizophrenia, mood disorders, and addiction.
Trace amines have been shown to act on a novel group of mammalian seven transmembrane spanning G protein-coupled receptors belonging to the rhodopsin superfamily, cloned in 2001. The receptor encoded by the human TAAR1 gene is also present in rat and mouse genomes and has been shown to be activated by endogenous trace amine ligands, including p-tyramine and β-phenylethylamine. A number of drugs, most notably amphetamine and its derivatives, act as agonists at this receptor.
In the brain, phenethylamine regulates monoamine neurotransmission by binding to trace amine-associated receptor 1 (TAAR1) and inhibiting vesicular monoamine transporter 2 (VMAT2) in monoamine neurons. It stimulates the release of norepinephrine and dopamine and is metabolized by monoamine oxidases as well as other enzymes.
PEA increases extracellular levels of dopamine and modulates noradrenergic transmission. PEA is a neurotransmitter and a hormone, and may act as a neuromodulator for catecholamines. PEA increases extracellular levels of dopamine and modulates noradrenergic transmission. PEA also antagonizes GABA(B) receptors, suppressing their inhibitory effects.
A review of the literature indicates that brain phenylethylamine (PEA) may be a neuromodulator of aminergic synapses and that it promotes energy, elevates mood, and favors aggression.
PEA is a trace amine whose molecular mechanism of action differs from biogenic amines, such as serotonin or dopamine. To a lesser extent, it also acts as a neurotransmitter in the human central nervous system.
PEA is a monoamine alkaloid that acts as a central nervous system stimulant in humans. Research has shown that PEA exerts antidepressant effects by modulating the Brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB)/cAMP response element binding protein (CREB) signaling pathway in corticosterone-induced depression models. Investigation into hippocampal neurons found that treatment with PEA rescued dendritic spine formation via regulation of BDNF/TrkB/CREB signaling. This mechanism, however, has been characterized only in preclinical (animal and cell) models and has not been confirmed in human trials.
Evidence level: Preliminary; limited, small, uncontrolled human studies.
Phenylacetic acid, the main metabolite of PEA, is decreased in the biological fluids of depressed subjects and schizophrenic subjects and is increased in schizoaffective subjects. The administration of PEA or of its precursor L-phenylalanine improves mood in depressed patients treated with a selective monoamine oxidase B inhibitor. The authors speculate that studies of PEA metabolism may have diagnostic value and that PEA administration may be therapeutic in selected depressed patients.
Mean total plasma PAA (phenylacetic acid) concentrations were 491.83 ± 232.84 ng/ml in 12 healthy volunteers and 300.33 ± 197.44 ng/ml in 23 drug-free patients with major depression. The 24-hour urinary PAA excretion was also measured in 48 healthy volunteers (141.1 ± 10.2 mg PAA/24 hr) and in 144 patients with major depression (78.2 ± 41.0 mg PAA/24 hr). The results suggest that low plasma and urinary PAA may be state markers for depression and are compatible with the PEA hypothesis. In the same study, phenylalanine elevated mood in 31 of 40 depressives.
The most frequently cited human intervention study is a follow-up report published in the Journal of Neuropsychiatry and Clinical Neurosciences (Sabelli et al., 1996). Phenylethylamine (PEA), an endogenous neuroamine, increases attention and activity in animals and has been shown to relieve depression in 60% of depressed patients. It has been proposed that PEA deficit may be the cause of a common form of depressive illness. Fourteen patients with major depressive episodes that responded to PEA treatment (10–60 mg orally per day, with 10 mg/day selegiline to prevent rapid PEA destruction) were reexamined 20 to 50 weeks later. The antidepressant response had been maintained in 12 patients. Effective dosage did not change with time. There were no apparent side effects. PEA produces sustained relief of depression in a significant number of patients, including some unresponsive to the standard treatments.
PEA improves mood as rapidly as amphetamine but does not produce tolerance.
Despite these findings, the evidence base for PEA as an antidepressant remains critically limited. The key study involved only 14 patients, lacked a placebo control or randomization, and was necessarily co-administered with selegiline (a selective MAO-B inhibitor) to prevent pre-systemic metabolism. No large randomized controlled trials (RCTs) have been published. Supplementation with PEA has been presumed to have antidepressant effects. Supplementation with phenylalanine has been recommended for decades, although few controlled studies exist to investigate claims of effectiveness.
Contradicting the simple "PEA deficit" hypothesis, one study of hospitalized depressed patients found that depression is not associated with a generalized PEA deficit and that PAA reductions, previously reported in a depressed patient population, may not reflect a PEA abnormality.
Evidence level: Preliminary; based primarily on biomarker studies, not intervention trials.
A study examined urinary excretion (24-hr) of beta-phenylethylamine (PEA), phenylacetic acid (PAA), phenylalanine (Phe), and p-tyrosine (Tyr), and plasma levels of PAA, Phe, and Tyr in 18 normal children and 26 children diagnosed as having attention-deficit hyperactivity disorder (ADHD). The results indicated that urinary excretion (expressed per g of creatinine) of free and total PEA was significantly lower in the ADHD patients, and plasma levels of Phe and Tyr were also decreased in the ADHD subjects compared with the normal controls.
In a number of controlled studies, by measuring urinary excretion levels, PEA was found to be significantly lower in children with ADHD and learning disability (LD). Separate research found that methylphenidate (Ritalin) treatment in children with ADHD significantly raised urinary PEA levels.
However, whether that deficiency causes ADHD symptoms or results from them — or both — is genuinely unresolved. Causation here is genuinely unresolved. Clinical evidence remains limited, and PEA's rapid breakdown by MAO-B enzyme severely limits bioavailability from supplements, making its therapeutic benefit unclear without medical supervision.
Evidence level: Associative/biomarker only; inconsistent findings; no therapeutic intervention trials.
Excess phenylethylamine has been invoked particularly in paranoid schizophrenia, in which it is thought to act as an endogenous amphetamine and, therefore, would be antagonized by neuroleptics. The importance of phenylethylamine in mental disorders is far from fully elucidated but the evolution of phenylethylamine concentrations in relation to symptoms remains a worthwhile investigation for individual psychotic patients.
PEA shares structural and physiological similarities with the amphetamines, the administration of which can induce a schizophrenia-like psychosis. While there are a number of reports of high urinary PEA excretion in schizophrenic patients, the measurement of PEA in other body fluids and the measurement of phenylacetic acid (the major metabolite of PEA) has resulted in inconsistent findings. The use of neuroleptic medication is a major confounding variable in most of the clinical studies. If PEA does have a role in the etiology of schizophrenia, the mechanism may involve PEA's ability to amplify dopamine responses.
Evidence level: Speculative/associative; no controlled human intervention trials for supplemental PEA and exercise outcomes.
There is evidence that phenylethylamine may have similar effects as natural endorphins and serve as a possible factor in the antidepressant actions of exercise. It seems to be involved in the "runner's high" (described as a state of calm euphoria) that is experienced during and after physical exercise. This hypothesis is based on biomarker observations showing elevated urinary PEA during exercise, not on randomized trials of PEA supplementation for athletic performance.
Evidence level: Speculative; mechanism-based only; no published human clinical trials.
PEA is included in a number of weight-loss supplement formulations. The rationale is based on its sympathomimetic properties — PEA is known to increase norepinephrine and epinephrine levels in the body, which can boost metabolism. No published randomized controlled trials in humans have investigated PEA supplementation as a weight-loss intervention as a standalone agent. The evidence for this use is entirely mechanistic or anecdotal.
Research using animal and cellular models has shown that PEA exerts antidepressant effects by modulating the BDNF/TrkB/CREB signaling pathway. In hippocampal neuron experiments, treatment with PEA rescued dendritic spine formation via regulation of BDNF/TrkB/CREB signaling.
Regarding high-dose concerns, animal studies are important for safety context. PEA caused dose-dependent generation of hydroxyl radicals in vitro in Fenton's reaction in test tubes, in isolated mitochondrial fraction, and in vivo in the striatum of mice. A significant inhibition of NADH-ubiquinone oxidoreductase (complex-I) activity suggests the inhibition of oxidative phosphorylation in the mitochondria resulting in hydroxyl radical generation. However, per-oral administration of higher doses of PEA (75–125 mg/kg; 7 days) failed to cause such overt neurochemical effects in rats, which suggested safe consumption of food items rich in this trace amine by normal population.
A key pharmacokinetic limitation governs all assessments of supplemental PEA. In orally ingested phenethylamine, a significant amount is metabolized in the small intestine by monoamine oxidase B (MAO-B) and then aldehyde dehydrogenase (ALDH), which converts it to phenylacetic acid. The pharmacological profile of phenylethylamine is characterized by its rapid absorption and metabolism. Monoamine oxidase-B (MAO-B) enzymes quickly break down phenylethylamine in the gut and liver, limiting its bioavailability when taken orally. This rapid degradation explains why dietary sources rarely produce significant psychoactive effects.
According to Alexander Shulgin in PiHKAL, phenethylamine is completely inactive in humans at doses of up to 1,600 mg orally and 50 mg intravenously. This observation underscores the profound first-pass effect and has led researchers to explore combinations with MAO-B inhibitors to extend the compound's half-life in the brain.
The following dosages appear specifically in published or cited studies and should not be taken as general recommendations:
No regulatory body (FDA, EFSA, EMA) has established a reference daily intake or safe upper level for supplemental PEA. Despite the lack of effectiveness and safety data, dietary supplements are widely available. The salt form, phenylethylamine HCl, is the most common phenylethylamine supplement, and phenylethylamine powders and tablets are also sold. Slow-release versions of phenethylamine have been developed, designed to slowly release phenethylamine over time to prolong its effects. They have not been tested in clinical trials. There is no clinical evidence to support the efficacy of these supplements.
In humans, phenethylamine is oxidized by MAO-B to form the inactive metabolite phenylacetic acid. Animal research shows that administering an MAOI prior to phenethylamine increases the amphetamine-like effects of phenethylamine. However, low-quality clinical research has used phenethylamine with selegiline, an MAOI, with apparent safety.
Trace amines such as p-tyramine and β-phenylethylamine are found endogenously as well as in the diet. Concomitant ingestion of these foodstuffs with monoamine oxidase inhibitors may result in the hypertensive crisis known as the "beer, wine, and cheese effect" attributed to their sympathomimetic action.
Trace amines are known, albeit at greatly supraphysiological levels, to raise blood pressure on account of their propensity to exert potent indirect sympathomimetic effects; additionally, some research posits that trace amines may induce vasoconstrictive effects partly or wholly separate therefrom, which would then constitute a second hypertensive mechanism.
People taking MAO inhibitors, or those who have a condition known as phenylketonuria (PKU), should not take phenethylamine. These disorders prevent the metabolism of phenylalanine in the body, which can lead to negative side effects such as severe headaches and hypertension, or even psychosis.
People suffering from schizophrenia or bipolar disorder should avoid this supplement. The supplement may cause a patient with bipolar disorder to shift from depression to mania. Schizophrenia patients should also use caution, as research indicates it may increase hallucinations and delusions.
Potential interactions have been noted with monoamine oxidase inhibitors (MAOIs) used for depression or Parkinson's disease, stimulants such as amphetamine, lisdexamfetamine, or methylphenidate, and products that contain caffeine. As with most dietary supplements, the research on drug interactions with phenethylamine is incomplete.
Long-term over-consumption of PEA-containing food items could be a neurological risk factor having significant pathological relevance to disease conditions such as depression or motor dysfunction. This finding derives from a mouse study and has not been confirmed in controlled human research.
PEA causes the release of nor-epinephrine into the synaptic space, which consequently constricts the aorta and the coronary arteries. However, results among various studies are inconclusive, and the connection between chocolate-derived PEA and migraines remains unresolved.
Not enough is known about the safety of using phenethylamine during pregnancy, breastfeeding, and childhood.
Anesthetics may also interact with phenethylamine. This interaction has not been characterized in controlled human research.
Phenylethylamine is not a scheduled substance in the United States. It is sold openly as a dietary supplement but, as noted, carries no FDA approval for any therapeutic use.
The overall evidence base for supplemental PEA in humans is preliminary and limited. The compound has a well-characterized endogenous biochemistry — as a TAAR1 agonist, monoamine releaser, and MAO-B substrate — but translating this into clinically meaningful supplementation is complicated by its extremely rapid first-pass metabolism. PEA is a trace amine whose molecular mechanism of action differs from biogenic amines such as serotonin or dopamine, and especially low or high concentrations of PEA may be associated with specific psychological disorders. Available human studies are small, unblinded, not placebo-controlled, and often conducted with co-administered MAO-B inhibitors. No large RCTs have been published. Biomarker studies (urinary PAA and PEA) provide associative — not causal — evidence linking PEA levels to depression and ADHD. Regulatory bodies have not approved PEA for any indication, and no official monograph (WHO, ESCOP, Commission E, USP) for PEA as a botanical or dietary supplement has been established.
Health conditions that PEA (phenylethylamine) may help support.
Body systems that PEA (phenylethylamine) may help support.
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