Phenylalanine is an amino acid that constructs proteins, neurotransmitters, and other essential particles in your body. The body can’t produce phenylalanine, that makes it a necessary amino acid we need to receive from food.

Nutritional supplements can consist of different types of phenylalanine with distinct mechanisms and health effects– we’ll dive into details about each one.


Phenylalanine particle has 2 various types, 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 form that takes place naturally in a range of foods. Your body uses it to make proteins and other molecules.

D-phenylalanine is the synthetic type made in the laboratory. Your body partly transforms it to the L-form or eliminates it through urine, but it likewise has some particular health results talked about listed below.

Supplements can consist of either form or a mix of their equivalent quantities, called DLPA (DL-phenylalanine). [1]


The hereditary codon for phenylalanine was the first to be found. Marshall W. Nirenberg found that insertion of m-RNA comprised of numerous uracil repeats into E. coli, the bacterium produced a new protein, comprised entirely of repeated phenylalanine amino acids.


Phenylalanine can not be made by animals, which need to get it from their diet plan. It is produced by plants and the majority of microbes from prephenate, an intermediate on the shikimate path.

Prephenate is decarboxylated with loss of the hydroxyl group to provide phenylpyruvate. This types is transaminated using glutamate as the nitrogen source to offer 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 more converted into dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline) (the latter three are referred to as the catecholamines).

Phenylalanine uses the very same active transport channel as tryptophan to cross the blood-brain barrier, and, in large amounts, disrupts 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 called “phenylketonurics” and need to avoid intake of phenylalanine. This dietary constraint also applies to pregnant females with hyperphenylalanine (high levels of phenylalanine in blood) since they do not effectively metabolize the amino acid phenylalanine. Persons experiencing PKU must monitor their intake of protein to manage the accumulation of phenylalanine as their bodies convert protein into its component amino acids.

An associated concern is the compound present in lots of sugarless gums and mints, snack foods, sugarless sodas (such as diet plan sodas including CocaCola No, Pepsi Max, some types of Lipton Tea, diet Nestea, Clear Splash flavored water), and a number of other low calorie food products. The sweetening agent aspartame, offered under the names “Equal” and “NutraSweet”, is an ester that is hydrolyzed in the body to give phenylalanine, aspartic acid, and methanol (wood alcohol). The breakdown problems phenylketonurics have with protein and the attendant develop of phenylalanine in the body likewise accompanies the ingestion of aspartame, although to a lower degree. Appropriately, all products in the U.S. and Canada that contain aspartame must be labeled: “Phenylketonurics: Contains phenylalanine.” In the UK, foods including aspartame should bring components panels that describe the existence of ‘aspartame or E951’, [1] and they should be labeled with a caution “Consists of a source of phenylalanine”. These cautions are particularly positioned to aid individuals 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 a mutation that is discovered in human beings who have PKU.

D- and DL-phenylalanine

D-phenylalanine (DPA) either as a single enantiomer or as an element of the racemic mixture is offered through traditional natural synthesis. It does not take part in protein biosynthesis although it is found in proteins, in percentages, particularly aged proteins and food proteins that have been processed. The biological functions of D-amino acids stay uncertain. Some D-amino acids, such as D-phenylalanine, may have pharmacological 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 explained by the possible clog by D-phenylalanine of enkephalin destruction 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. Raised brain norepinephrine and dopamine levels are thought to be related to antidepressant impacts. D-phenylalanine is absorbed from the small intestine, following intake, and carried to the liver through the portal blood circulation. A fraction of D-phenylalanine appears to be transformed to L-phenylalanine. D-phenylalanine is dispersed to the numerous tissues of the body through the systemic circulation. D-phenylalanine appears to cross the blood-brain barrier with less effectiveness than L-phenylalanine. A portion of an ingested dosage of D-phenylalanine is excreted in the urine. [2]


Researchers consider phenylalanine to be an important amino acid. This suggests that the body is not able to produce its own phenylalanine. Rather, an individual should get phenylalanine from dietary sources.

One 2020 study explains that since phenylalanine belongs of many natural proteins, high protein foods are excellent sources of this vital 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 compounds that are low in phenylalanine include:.

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

Uses & & effectiveness Possibly Effective for …

A skin problem called vitiligo. Taking L-phenylalanine by mouth in combination with UVA direct exposure or using L-phenylalanine to the skin in combination with UVA exposure appears to be effective for dealing with vitiligo in adults and in children.

Potentially Ineffective for …

  • Attention deficit-hyperactivity condition (ADHD). Some research study recommends that patients with ADHD have lower levels of amino acids such as phenylalanine, so there was hope that providing phenylalanine may treat ADHD. However, taking phenylalanine by mouth does not seem to have any impact on ADHD symptoms.
  • Taking D-phenylalanine by mouth does not require to lower discomfort.

Inadequate Evidence to Rate Efficiency for …

  • Acupuncture anesthesia. Early research recommends 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 neck and back pain.
  • Early research suggests that taking a combination of D-phenylalanine, L-glutamine, and L-5-hydroxytryptophan for 40 days can improve some symptoms of alcohol withdrawal.
  • Minimal clinical research carried out in the 1980s suggests L-phenylalanine or DL-phenylalanine might be beneficial for depression. However, this research requires to be verified. Taking D-phenylalanine does not appear to enhance signs of depression.
  • Several sclerosis. Early research suggests that using Cari Loder’s regiment, which includes L-phenylalanine, lofepramine, and intramuscular vitamin B12 for 24 weeks, does not enhance disability in individuals with several sclerosis.
  • Parkinson’s disease. Restricted research suggests taking one type of phenylalanine (D-phenylalanine) may reduce symptoms of Parkinson’s illness. However, taking another type (DL-phenylalanine) does not appear to work.
  • Phenylalanine shortage. Early research suggests that taking phenylalanine by mouth might enhance phenylalanine deficiency in kids with tyrosinemia.
  • Other conditions. [4]


1. Used to Produce Other Substances

Like other amino acids, phenylalanine plays a vital role in the production of other key substances that are important to health. For example, it’s utilized to produce dopamine, a neurotransmitter that is involved in knowing, memory and feeling.

The body likewise transforms phenylalanine to tyrosine, an amino acid that assists 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, depression, amnesia and low energy levels.

2. Might Reduce Signs of Depression

One of the leading L-phenylalanine benefits is its ability to enhance mood and protect against depression. Although more research study is needed, some research studies have found that it could have powerful mood-boosting homes.

In fact, a research study released in the Journal of Neural Transmission found that administering 75– 200 milligrams of DL-phenylalanine (DLPA) per day to 20 people improved a number of symptoms of anxiety, consisting of general mood and agitation. Another study found that integrating L-phenylalanine with L-deprenyl, a medication used to prevent the breakdown of dopamine, had a helpful result on symptoms of depression in 90 percent of outpatient individuals.

3. Could Aid in Treatment of Parkinson’s Disease

Parkinson’s illness is a condition that impacts the central nervous system, causing symptoms like tremors, stiffness and slow movement. According to a research study in the International Journal of General Medicine, Parkinson’s disease is also characterized by a depletion of tyrosine, dopamine and norepinephrine, all of which are synthesized from phenylalanine.

Although one study did discover that phenylalanine could be healing in the treatment of Parkinson’s illness, additional premium human trials ought to be conducted to determine how it might impact symptoms.

4. Relieves Chronic Discomfort

Some research has actually found that phenylalanine could function as a natural painkiller to help in reducing and handle chronic discomfort. One study even reported that it has actually been shown to have analgesic residential or commercial properties in both human and animal trials, noting that it might help reduce discomfort brought on by a range of conditions.

Another animal study revealed that injecting horses with a mix of amino acids, consisting of D-phenylalanine and D-leucine, helped in reducing persistent pain by protecting the activity of specific endorphins in the brain.

5. Might Promote Weight-loss

Does L-phenylalanine help with weight-loss? While more research studies on the link between L-phenylalanine and weight-loss are certainly needed, some emerging proof reveals that phenylalanine might have a huge effect when it pertains to your midsection.

A study carried out by the Department of Gastroenterology at St. Bartholomew’s Hospital in London in fact found that administering L-phenylalanine to 10 individuals before meals minimized food intake and increased levels of cholecystokinin (CCK), a hormone that promotes food digestion and helps keep cravings under control. Another in vitro study in the American Journal of Physiology had comparable findings, keeping in mind that phenylalanine had the ability to increase secretion of CCK, which might possibly help in weight-loss. [5]

Research research study

Effect of co-trimoxazole on phenylalanine metabolism in guy

An examination was finished 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 in between serum-phenylalanine and tyrosine was similarly high. In a couple of patients, serum phenylalanine levels were marginally brought up in fasting conditions. As a conclusion, it was proposed that the trimethoprim/sulfamethoxazole blend has a synergistic activity in offending phenylalanine resistance.

An open research study on phenylalanine in depressed patients

In a medical trial, phenylalanine was regulated 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 handled and there was no further need of treatment for these clients. Mellow to direct reaction was seen in 4 clients. 4 clients did not react at all to phenylalanine. This examination shows that phenylalanine is significant in depressive clients.

Schizophrenia and blockage of dopaminergic neurotransmission

Phenylalanine is hydroxylated to tyrosine and tyrosine to dopa and dopa to dopamine. Dopamine has 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 furnished help for clients with positive manifestations [41] In any case, simply dopamine blockage is not sufficient to alleviate manifestations of schizophrenia in the way it is deemed those various neurotransmitters are additionally associated with pathophysiology of schizophrenia. Dopamine partiality for dopamine receptor is decreased by broadening adenosinergic transmission. Adenosine level might be expanded by discussion of allopurinol that is xanthine oxidase inhibitor, at last triggering antipsychotic and anxiolytic effects. Confirmation for this treatment has been represented in both case reports and little medical trials. Various investigations show that allopurinol is important in those patients who are ineffectively receptive to existing treatment for schizophrenia. Nevertheless, furthermore study ought to be completed to discover its practicality and wellbeing as a standard treatment for schizophrenia. In any case, shows consider demonstrate that allopurinol at 300 mg day by day is sufficient to assuage side effects of schizophrenia.

Effect of packing measurements of phenylalanine in unipolar dissuaded clients with and without tardive dyskinesia (TD)

In a scientific trial, phenylalanine was handled to 3 distinct events. Dosage of medication was 100 mg/kg phenylalanine. Eleven patients were in first gathering (discouraged clients with tardive dyskinesia). Ten clients remained in second event (dissuaded client provided to neuroleptics yet without TD), 10 patients remained in third gathering (patients never ever provided to NLs). There was no critical factual contrast among three gatherings. A relationship was found in between automatic advancement and fasting, and phenylalanine stacking following 2 hours. 3 TD clients showed remarkably expansive increments in phenylalanine level in plasma. This assessment demonstrated that variations from the norm in digestion of phenylalanine add to the enhancement and severity of TD in some NL-treated unipolar prevented clients. [6]

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

Phenylalanine isn’t a health issue for the majority of people. However, for people who have the genetic disorder phenylketonuria (PKU) or certain other health conditions phenylalanine can be a serious health concern.

Phenylalanine can cause intellectual specials needs, brain damage, 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 sweetening agent aspartame (Equal, NutraSweet), which is contributed to numerous medications, diet plan foods and diet sodas, includes phenylalanine.

Federal policies require that any drink or food that contains aspartame bear this caution: “Phenylketonurics: Contains phenylalanine.” This warning assists individuals with PKU prevent products that give phenylalanine.

If you don’t have PKU, you most likely do not require to fret about harmful health impacts of phenylalanine– with specific important exceptions. Aspartame in large doses can trigger a fast increase in brain levels of phenylalanine. Because of this, use products with aspartame carefully if you:.

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

Have the muscle motion disorder tardive dyskinesia.

Have a sleep condition, anxiety condition or other psychological health condition; phenylalanine might aggravate feelings of anxiety and jitteriness.

If you aren’t sure if phenylalanine or aspartame is a concern for you, talk with your medical professional. A blood test to identify if you have PKU is available and is now consistently done as part of newborn screening. [7]

How It Functions?

How to Utilize It?

DLPA has actually been utilized in amounts varying from 75– 1,500 mg per day. This compound can have effective effects on state of mind and on the nervous system, and for that reason DLPA must be taken only under medical supervision. LPA has actually been utilized in amounts up to 3.5 grams daily. For best results, phenylalanine must be taken in between meals, since the protein present in food can disrupt the uptake of phenylalanine into the brain, possibly minimizing its result.

Where to Discover It?

LPA is found in the majority of foods that contain protein. DPA does not usually occur in food. Nevertheless, 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 also be manufactured separately, but it is more pricey to do so. The combination supplement (DLPA) is often used because of the lower expense and due to the fact that both parts put in different health-enhancing results.

Possible Deficiencies

Individuals whose diet plans are really low in protein may establish a deficiency of LPA, although this is thought to be extremely uncommon. Nevertheless, one does not necessarily need to lack LPA in order to gain from a DLPA supplement. [8]

What are the dangers of taking phenylalanine?

Phenylalanine can trigger allergies, with signs such as:.

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

Negative effects may consist of:

  • Heartburn
  • Tiredness
  • Queasiness
  • Constipation
  • Dizziness
  • Headache
  • Anxiety and hypomania (a milder type of mania)
  • Sedation
  • Jitteriness and trouble sleeping
  • Dosages higher than 5,000 milligrams a day can trigger nerve damage.

Threats. Individuals with specific conditions ought to avoid using this supplement, consisting of those with schizophrenia (tardive dyskinesia, a motion condition, might establish.) You likewise must prevent the supplement if you have a sensitivity to phenylalanine or a condition in which your body can’t break down phenylalanine such as phenylketonuria (PKU).

And use care in taking phenylalanine if you have:.

  • Hypertension
  • Difficulty sleeping
  • Stress and anxiety or other psychiatric problems
  • Also, it is unidentified whether this supplement is safe in women who are pregnant or breastfeeding. [9]

Preventative measures

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

Individuals with phenylketonuria (PKU), and females who are breastfeeding or are pregnant, ought to not take phenylalanine supplements. Aspartame, found in sweetening agents such as Nutrasweet, gives phenylalanine. Individuals with PKU must not use aspartame. If you are pregnant, ask your medical professional about utilizing this sweetening agent.

DL-phenylalanine must not be used in people taking antipsychotic drugs, as it may cause or worsen symptoms of tardive dyskinesia (TD). TDs are involuntary motions of the tongue, lips, face, trunk, and limbs that can occur in individuals taking antipsychotic drugs long term.

DL-phenylalanine might cause symptoms of stress and anxiety, jitteriness, and hyperactivity in kids.

Doses higher than 5,000 mg a day might be toxic and can cause nerve damage. High amounts of DL-phenylalanine might cause moderate negative effects such as queasiness, heartburn, and headaches.

Possible Interactions

If you are currently being treated with medication (specifically the following medications), you ought to not use phenylalanine without first talking with your health care provider.

Monoamine Oxidase Inhibitors: Monoamine oxidase inhibitors (MAOIs) are an older class of antidepressants drugs that are hardly ever utilized now. They consist of phenelzine (Nardil), isocarboxazid (Marplan), and tranylcypromine sulfate (Parnate). Taking phenylalanine while taking MAOIs might cause an extreme boost in blood pressure (hypertensive crisis). This extreme increase in blood pressure can cause a cardiac arrest or stroke. People taking MAOIs need to prevent foods and supplements consisting of phenylalanine.

Baclofen: Phenylalanine may decrease absorption of baclofen (Lioresal), a medication utilized to ease muscle spasms. Prevent taking Baclofen with a meal, particularly one that is high in protein, or with phenylalanine supplements.

Levodopa: A few case reports suggest that phenylalanine might lower the efficiency of levodopa (Sinemet), a medication used to deal with Parkinson disease. Some scientists believe phenylalanine might hinder the absorption of levodopa and worsen the individual’s condition.

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

Antipsychotic or neuroleptic drugs: L-phenylalanine may intensify TD, a negative effects of these neuroleptic drugs. These drugs include phenytoin (Dilantin), valproic acid (Depakene, Depakote), and carbamazepine (Tegretol), among others. [10]


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

It might benefit the skin condition vitiligo, however research on its results on depression, pain, and other conditions is limited.

While it’s typically thought about safe for healthy people, it’s important that those with phenylketonuria (PKU) keep their consumption low to avoid possibly unsafe side effects.

If you see any negative side effects after taking a phenylalanine supplement or consuming high protein foods, talk with your doctor.

They can test your amino acid blood levels and help determine the very best course of treatment for you. [11]


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