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Phenylalanine is an amino acid that constructs proteins, neurotransmitters, and other essential molecules in your body. The body can’t produce phenylalanine, which makes it an important amino acid we need to get from food.

Nutritional supplements can consist of various types of phenylalanine with special systems and health results– we’ll dive into information about every one.


Phenylalanine particle has 2 various kinds, L- and D-phenylalanine, which are “mirror images” with the exact same structure. As you can see in the image above, they are just differently oriented in space.

L-phenylalanine is the active kind that occurs naturally in a range of foods. Your body uses it to make proteins and other molecules.

D-phenylalanine is the synthetic form made in the lab. Your body partially transforms it to the L-form or removes it by means of urine, but it also has some specific health effects discussed listed below.

Supplements can contain either form or a mixture of their equivalent amounts, known as DLPA (DL-phenylalanine). [1]


The genetic codon for phenylalanine was the first to be discovered. Marshall W. Nirenberg found that insertion of m-RNA made up of numerous uracil repeats into E. coli, the germs produced a new protein, made up solely of duplicated phenylalanine amino acids.


Phenylalanine can not be made by animals, which have to get it from their diet plan. It is produced by plants and most bacteria from prephenate, an intermediate on the shikimate pathway.

Prephenate is decarboxylated with loss of the hydroxyl group to give phenylpyruvate. This types is transaminated utilizing glutamate as the nitrogen source to provide phenylalanine and α-ketoglutarate.

Other biological roles

L-phenylalanine can likewise be converted into L-tyrosine, another one of the DNA-encoded amino acids. L-tyrosine in turn is converted into L-DOPA, which is further converted into dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline) (the latter 3 are known as the catecholamines).

Phenylalanine uses the exact same active transportation channel as tryptophan to cross the blood-brain barrier, and, in big amounts, interferes with the production of serotonin.

Lignin is originated from phenylalanine and from tyrosine. Phenylalanine is converted to cinnamic acid by the enzyme phenylalanine ammonia lyase.


The congenital disease phenylketonuria (PKU) is the failure to metabolize phenylalanine. People with this disorder are referred to as “phenylketonurics” and need to abstain from intake of phenylalanine. This dietary constraint also applies to pregnant women with hyperphenylalanine (high levels of phenylalanine in blood) because they do not correctly metabolize the amino acid phenylalanine. Persons experiencing PKU needs to monitor their consumption of protein to manage the buildup of phenylalanine as their bodies convert protein into its part amino acids.

An associated issue is the substance present in lots of sugarless gums and mints, junk food, sugarless soft drinks (such as diet plan sodas including CocaCola Zero, Pepsi Max, some forms of Lipton Tea, diet Nestea, Clear Splash flavored water), and a variety of other low calorie food. The artificial sweetener aspartame, sold under the names “Equal” and “NutraSweet”, is an ester that is hydrolyzed in the body to provide phenylalanine, aspartic acid, and methanol (wood alcohol). The breakdown issues phenylketonurics have with protein and the attendant develop of phenylalanine in the body also accompanies the ingestion of aspartame, although to a lesser degree. Accordingly, all items in the U.S. and Canada that contain aspartame needs to be identified: “Phenylketonurics: Contains phenylalanine.” In the UK, foods containing aspartame must bring components panels that refer to the existence of ‘aspartame or E951’, [1] and they should be labeled with a warning “Consists of a source of phenylalanine”. These warnings are particularly placed to aid people who suffer from PKU so that they can prevent such foods.

Surprisingly, the macaque genome was just recently sequenced and it was discovered that macaques naturally have an anomaly that is found in people who have PKU.

D- and DL-phenylalanine

D-phenylalanine (DPA) either as a single enantiomer or as a component of the racemic mixture is offered through conventional natural synthesis. It does not participate in protein biosynthesis although it is discovered in proteins, in small amounts, particularly aged proteins and food proteins that have been processed. The biological functions of D-amino acids stay unclear. Some D-amino acids, such as D-phenylalanine, may have medicinal activity.

DL-Phenylalanine is marketed as a dietary supplement for its putative analgesic and antidepressant activities. The putative analgesic activity of DL-phenylalanine might be described by the possible clog by D-phenylalanine of enkephalin degradation by the enzyme carboxypeptidase A. The mechanism of DL-phenylalanine’s putative antidepressant activity may be represented by the precursor function of L-phenylalanine in the synthesis of the neurotransmitters norepinephrine and dopamine. Elevated brain norepinephrine and dopamine levels are thought to be associated with antidepressant effects. D-phenylalanine is absorbed from the small intestine, following consumption, and transferred to the liver through the portal flow. A portion of D-phenylalanine appears to be converted to L-phenylalanine. D-phenylalanine is distributed to the numerous tissues of the body via the systemic circulation. D-phenylalanine appears to cross the blood-brain barrier with less efficiency than L-phenylalanine. A fraction of a consumed dose of D-phenylalanine is excreted in the urine. [2]


Researchers think about phenylalanine to be a vital amino acid. This means that the human body is not able to produce its own phenylalanine. Instead, an individual needs to get phenylalanine from dietary sources.

One 2020 study discusses that since phenylalanine belongs of lots of natural proteins, high protein foods are great sources of this important amino acid.

Some examples of high protein foods consist of:.

  • meat
  • fish
  • eggs
  • milk
  • cheese
  • gelatin
  • grains, such as:
  • wheat
  • oats
  • quinoa
  • barley
  • rye
  • lentils
  • nuts and seeds
  • soy items and tempeh
  • plant-based “meat” products
  • plant algae
  • the sweetener aspartame

Foods and substances that are low in phenylalanine consist of:.

  • fruits
  • vegetables
  • fats
  • sugars
  • starches [3]

Uses & efficiency

Potentially Efficient for …

A skin condition called vitiligo. Taking L-phenylalanine by mouth in combination with UVA exposure or using L-phenylalanine to the skin in mix with UVA direct exposure seems to be reliable for dealing with vitiligo in grownups and in kids.

Possibly Inefficient for …

  • Attention deficit-hyperactivity condition (ADHD). Some research recommends that clients with ADHD have lower levels of amino acids such as phenylalanine, so there was hope that supplying phenylalanine might deal with ADHD. However, taking phenylalanine by mouth does not appear to have any effect on ADHD symptoms.
  • Taking D-phenylalanine by mouth does not require to minimize pain.

Insufficient Proof to Rate Effectiveness for …

  • Acupuncture anesthesia. Early research study suggests that taking D-phenylalanine by mouth might improve acupuncture anesthesia while having a tooth pulled. Nevertheless, it does not seem to enhance acupuncture anesthesia for pain in the back.
  • Early research suggests that taking a mix of D-phenylalanine, L-glutamine, and L-5-hydroxytryptophan for 40 days can enhance some symptoms of alcohol withdrawal.
  • Limited clinical research study performed in the 1980s recommends L-phenylalanine or DL-phenylalanine might be helpful for anxiety. Nevertheless, this research requires to be validated. Taking D-phenylalanine does not appear to improve signs of anxiety.
  • Several sclerosis. Early research study recommends that utilizing Cari Loder’s program, which includes L-phenylalanine, lofepramine, and intramuscular vitamin B12 for 24 weeks, does not enhance impairment in individuals with several sclerosis.
  • Parkinson’s disease. Restricted research suggests taking one kind of phenylalanine (D-phenylalanine) might decrease symptoms of Parkinson’s disease. However, taking another kind (DL-phenylalanine) does not seem to work.
  • Phenylalanine deficiency. Early research study recommends that taking phenylalanine by mouth might enhance phenylalanine shortage in kids with tyrosinemia.
  • Other conditions. [4]


1. Utilized to Produce Other Compounds

Like other amino acids, phenylalanine plays a vital function in the production of other crucial compounds that are essential to health. For example, it’s used to produce dopamine, a neurotransmitter that is involved in learning, memory and feeling.

The body likewise converts phenylalanine to tyrosine, an amino acid that aids in the synthesis of proteins. It’s likewise involved in the production of norepinephrine and epinephrine, both of which are neurotransmitters released by the body in response to stressful circumstances.

A deficiency in this crucial amino acid can cause a long list of signs, consisting of confusion, anxiety, memory loss and low energy levels.

2. May Reduce Signs of Depression

Among the leading L-phenylalanine benefits is its ability to enhance mood and safeguard versus depression. Although more research is required, some research studies have actually discovered that it might have effective mood-boosting properties.

In fact, a research study published in the Journal of Neural Transmission found that administering 75– 200 milligrams of DL-phenylalanine (DLPA) per day to 20 people enhanced several symptoms of anxiety, consisting of total state of mind and agitation. Another study found that integrating L-phenylalanine with L-deprenyl, a medication utilized to prevent the breakdown of dopamine, had an useful result on signs of anxiety in 90 percent of outpatient participants.

3. Could Help in Treatment of Parkinson’s Illness

Parkinson’s disease is a condition that impacts the central nerve system, causing signs like tremblings, stiffness and sluggish motion. According to a research study in the International Journal of General Medicine, Parkinson’s illness is also identified by an exhaustion of tyrosine, dopamine and norepinephrine, all of which are manufactured from phenylalanine.

Although one research study did find that phenylalanine could be healing in the treatment of Parkinson’s illness, additional high-quality human trials need to be conducted to identify how it might impact symptoms.

4. Relieves Persistent Discomfort

Some research study has actually found that phenylalanine could act as a natural pain reliever to help reduce and handle chronic pain. One research study even reported that it has been revealed to have analgesic residential or commercial properties in both human and animal trials, keeping in mind that it may help in reducing discomfort brought on by a variety of conditions.

Another animal study revealed that injecting horses with a mix of amino acids, including D-phenylalanine and D-leucine, helped in reducing chronic discomfort by preserving the activity of particular endorphins in the brain.

5. May Promote Weight Loss

Does L-phenylalanine assist with weight loss? While more studies on the link in between L-phenylalanine and weight loss are absolutely required, some emerging evidence reveals that phenylalanine could have a huge impact when it comes to your midsection.

A research study performed by the Department of Gastroenterology at St. Bartholomew’s Healthcare facility in London really discovered that administering L-phenylalanine to 10 individuals before meals minimized food intake and increased levels of cholecystokinin (CCK), a hormone that stimulates food digestion and helps keep cravings under control. Another in vitro study in the American Journal of Physiology had similar findings, keeping in mind that phenylalanine was able to increase secretion of CCK, which could possibly help in weight reduction. [5]

Research study

Impact of co-trimoxazole on phenylalanine metabolic process in man

An examination was completed to assess effect of co-trimoxazole on phenylalanine digestion. It was found that phenylalanine level remains high in the wake of taking co-trimoxazole. Percentage between serum-phenylalanine and tyrosine was likewise high. In a couple of patients, serum phenylalanine levels were marginally raised in fasting conditions. As a conclusion, it was proposed that the trimethoprim/sulfamethoxazole mix has a synergistic activity in angering phenylalanine resistance.

An open research study on phenylalanine in depressed clients

In a medical trial, phenylalanine was managed to 20 clients with gloom. Length of treatment was 20 days. Measurement of phenylalanine was 75– 200 mg/day. Toward the finish of treatment, 12 clients were dealt with and there was no more requirement of treatment for these clients. Mellow to direct response was seen in 4 clients. 4 patients did not react at all to phenylalanine. This examination shows that phenylalanine is considerable in depressive patients.

Schizophrenia and blockage of dopaminergic neurotransmission

Phenylalanine is hydroxylated to tyrosine and tyrosine to dopa and dopa to dopamine. Dopamine has actually been involved for a very long time in the pathophysiology of schizophrenia, and the run of the mill antipsychotics, by means of bar of dopaminergic neurotransmission, have provided assistance for clients with positive manifestations [41] In any case, simply dopamine obstruction is not adequate to reduce manifestations of schizophrenia in the method it is considered as those different neurotransmitters are in addition related to pathophysiology of schizophrenia. Dopamine partiality for dopamine receptor is lessened by broadening adenosinergic transmission. Adenosine level might be expanded by presentation of allopurinol that is xanthine oxidase inhibitor, at last triggering antipsychotic and anxiolytic impacts. Verification for this treatment has actually been accounted for in both case reports and little scientific trials. Various examinations demonstrate that allopurinol is valuable in those patients who are ineffectively receptive to existing treatment for schizophrenia. Nevertheless, additionally study ought to be finished to find its viability and wellbeing as a standard treatment for schizophrenia. In any case, exhibits think of demonstrate that allopurinol at 300 mg day by day is sufficient to assuage negative effects of schizophrenia.

Impact of packing measurements of phenylalanine in unipolar dissuaded patients with and without tardive dyskinesia (TD)

In a medical trial, phenylalanine was managed to 3 distinct events. Dose of medication was 100 mg/kg phenylalanine. Eleven patients were in very first gathering (prevented patients with tardive dyskinesia). Ten clients remained in 2nd gathering (dissuaded patient presented to neuroleptics yet without TD), 10 patients were in third event (clients never ever presented to NLs). There was no vital factual contrast among 3 events. A relationship was discovered in between automatic development and fasting, and phenylalanine stacking following 2 hours. Three TD clients suggested surprisingly expansive increments in phenylalanine level in plasma. This assessment demonstrated that variations from the norm in food digestion of phenylalanine add to the enhancement and severity of TD in some NL-treated unipolar dissuaded patients. [6]

My favorite diet plan soda has a warning about phenylalanine. Is phenylalanine bad for your health?

Phenylalanine isn’t a health issue for many people. However, for individuals who have the congenital disease phenylketonuria (PKU) or certain other health conditions phenylalanine can be a major health issue.

Phenylalanine can cause intellectual specials needs, mental retardation, seizures and other issues in people with PKU. Phenylalanine takes place naturally in lots of protein-rich foods, such as milk, eggs and meat. Phenylalanine is likewise sold as a dietary supplement.

The artificial sweetener aspartame (Equal, NutraSweet), which is added to many medications, diet foods and diet plan sodas, includes phenylalanine.

Federal regulations need that any drink or food which contains aspartame bear this warning: “Phenylketonurics: Contains phenylalanine.” This caution helps people with PKU prevent items that provide phenylalanine.

If you don’t have PKU, you probably don’t need to stress over hazardous health results of phenylalanine– with specific important exceptions. Aspartame in big dosages can cause a rapid boost in brain levels of phenylalanine. Because of this, usage items with aspartame meticulously if you:.

Take particular medications, such as monoamine oxidase inhibitors, neuroleptics or medications which contain levodopa (Sinemet, Rytary, others).

Have the muscle movement disorder tardive dyskinesia.

Have a sleep disorder, anxiety condition or other mental health condition; phenylalanine may intensify feelings of stress and anxiety and jitteriness.

If you aren’t sure if phenylalanine or aspartame is an issue for you, speak with your physician. A blood test to determine if you have PKU is readily available and is now routinely done as part of newborn screening. [7]

How It Works?

How to Use It?

DLPA has been utilized in amounts varying from 75– 1,500 mg each day. This substance can have powerful impacts on mood and on the nerve system, and for that reason DLPA must be taken only under medical supervision. LPA has actually been used in quantities up to 3.5 grams per day. For finest outcomes, phenylalanine ought to be taken between meals, because the protein present in food can interfere with the uptake of phenylalanine into the brain, possibly reducing its effect.

Where to Find It?

LPA is found in most foods that contain protein. DPA does not normally take place in food. However, when phenylalanine is synthesized in the laboratory, half appears in the L-form and the other half in the D-form. These 2 compounds can likewise be manufactured separately, however it is more pricey to do so. The combination supplement (DLPA) is often utilized because of the lower expense and because both components exert various health-enhancing results.

Possible Deficiencies

People whose diets are extremely low in protein might develop a shortage of LPA, although this is thought to be very uncommon. However, one does not necessarily need to be deficient in LPA in order to benefit from a DLPA supplement. [8]

What are the dangers of taking phenylalanine?

Phenylalanine can trigger allergic reactions, with symptoms such as:.

  • Itching
  • Swelling of the face or hands
  • Difficulty breathing
  • Tingling feeling in the mouth

Adverse effects might consist of:

  • Heartburn
  • Fatigue
  • Nausea
  • Irregularity
  • Dizziness
  • Headache
  • Anxiety and hypomania (a milder type of mania)
  • Sedation
  • Jitteriness and trouble sleeping
  • Doses higher than 5,000 milligrams a day can cause nerve damage.

Risks. People with specific conditions ought to prevent utilizing this supplement, including those with schizophrenia (tardive dyskinesia, a movement condition, might establish.) You also must prevent the supplement if you have a level of sensitivity to phenylalanine or a condition in which your body can’t break down phenylalanine such as phenylketonuria (PKU).

And utilize care in taking phenylalanine if you have:.

  • High blood pressure
  • Problem sleeping
  • Stress and anxiety or other psychiatric problems
  • Also, it is unidentified whether this supplement is safe in ladies who are pregnant or breastfeeding. [9]

Safety measures

Because of the capacity for negative effects and interactions with medications, you ought to only take dietary supplements under the supervision of a knowledgeable health care service provider.

People with phenylketonuria (PKU), and ladies who are breastfeeding or are pregnant, must not take phenylalanine supplements. Aspartame, found in artificial sweeteners such as Nutrasweet, gives phenylalanine. People with PKU should not use aspartame. If you are pregnant, ask your physician about utilizing this sweetening agent.

DL-phenylalanine needs to not be used in people taking antipsychotic drugs, as it might trigger or intensify symptoms of tardive dyskinesia (TD). TDs are involuntary movements of the tongue, lips, face, trunk, and limbs that can happen in individuals taking antipsychotic drugs long term.

DL-phenylalanine may cause signs of anxiety, jitteriness, and hyperactivity in children.

Dosages higher than 5,000 mg a day might be hazardous and can cause nerve damage. High quantities of DL-phenylalanine might trigger mild negative effects such as queasiness, heartburn, and headaches.

Possible Interactions

If you are presently being treated with medication (particularly the following medications), you should not utilize phenylalanine without first speaking with your healthcare service provider.

Monoamine Oxidase Inhibitors: Monoamine oxidase inhibitors (MAOIs) are an older class of antidepressants drugs that are rarely utilized now. They consist of phenelzine (Nardil), isocarboxazid (Marplan), and tranylcypromine sulfate (Parnate). Taking phenylalanine while taking MAOIs might trigger an extreme increase in blood pressure (hypertensive crisis). This extreme boost in blood pressure can result in a cardiac arrest or stroke. Individuals taking MAOIs should avoid foods and supplements including phenylalanine.

Baclofen: Phenylalanine might minimize absorption of baclofen (Lioresal), a medication used to relieve muscle spasms. Avoid taking Baclofen with a meal, particularly one that is high in protein, or with phenylalanine supplements.

Levodopa: A couple of case reports suggest that phenylalanine may decrease the efficiency of levodopa (Sinemet), a medication used to treat Parkinson disease. Some researchers believe phenylalanine may interfere with the absorption of levodopa and worsen the person’s condition.

Selegiline: L-phenylalanine and the selective MAO inhibitor selegiline (Eldepryl, Deprenyl) may reinforce the antidepressant impacts of phenylalanine. They should not be taken together.

Antipsychotic or neuroleptic drugs: L-phenylalanine may worsen TD, a side effect of these neuroleptic drugs. These drugs consist of phenytoin (Dilantin), valproic acid (Depakene, Depakote), and carbamazepine (Tegretol), to name a few. [10]


Phenylalanine is a necessary amino acid found in both plant and animal foods.

It might benefit the skin disorder vitiligo, however research study on its impacts on depression, discomfort, and other conditions is limited.

While it’s generally considered safe for healthy individuals, it is very important that those with phenylketonuria (PKU) keep their intake low to avoid potentially harmful adverse effects.

If you observe any negative adverse effects after taking a phenylalanine supplement or eating high protein foods, talk with your physician.

They can check your amino acid blood levels and assist figure out the best course of treatment for you. [11]


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