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

Nutritional supplements can contain various kinds of phenylalanine with special mechanisms and health effects– we’ll dive into details about each one.


Phenylalanine molecule has 2 various forms, L- and D-phenylalanine, which are “mirror images” with the very same structure. As you can see in the image above, they are just in a different way oriented in space.

L-phenylalanine is the active type that takes place naturally in a variety of foods. Your body utilizes it to make proteins and other particles.

D-phenylalanine is the synthetic type made in the lab. Your body partly converts it to the L-form or eliminates it by means of urine, but it likewise has some specific health effects discussed listed below.

Supplements can consist of either form or a mixture of their equal quantities, known as DLPA (DL-phenylalanine). [1]


The genetic codon for phenylalanine was the very first to be found. Marshall W. Nirenberg found that insertion of m-RNA comprised of multiple uracil repeats into E. coli, the bacterium 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. It is produced by plants and a lot of microbes from prephenate, an intermediate on the shikimate pathway.

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

Other biological functions

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 additional converted into dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline) (the latter 3 are known as the catecholamines).

Phenylalanine utilizes the same active transportation channel as tryptophan to cross the blood-brain barrier, and, in big quantities, hinders the production of serotonin.

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


The genetic disorder phenylketonuria (PKU) is the failure to metabolize phenylalanine. People with this condition are called “phenylketonurics” and should avoid usage of phenylalanine. This dietary constraint likewise applies to pregnant ladies with hyperphenylalanine (high levels of phenylalanine in blood) because they do not effectively metabolize the amino acid phenylalanine. Individuals suffering from PKU should monitor their consumption of protein to control the accumulation of phenylalanine as their bodies transform protein into its element amino acids.

A related concern is the compound present in lots of sugarless gums and mints, snack foods, sugarless sodas (such as diet plan sodas consisting of CocaCola No, 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, offered 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 problems phenylketonurics have with protein and the attendant build up of phenylalanine in the body also accompanies the intake of aspartame, although to a lower degree. Accordingly, all products in the U.S. and Canada that contain aspartame needs to be identified: “Phenylketonurics: Contains phenylalanine.” In the UK, foods including aspartame needs to bring components panels that describe the existence of ‘aspartame or E951’, [1] and they should be labeled with a caution “Includes a source of phenylalanine”. These cautions are specifically positioned to help people who suffer from PKU so that they can prevent such foods.

Remarkably, the macaque genome was just recently sequenced and it was discovered that macaques naturally have a mutation that is found in people who have PKU.

D- and DL-phenylalanine

D-phenylalanine (DPA) either as a single enantiomer or as a part of the racemic mix is readily available through conventional organic synthesis. It does not participate in protein biosynthesis although it is discovered in proteins, in small amounts, especially 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, might 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 described by the possible clog by D-phenylalanine of enkephalin destruction by the enzyme carboxypeptidase A. The mechanism of DL-phenylalanine’s putative antidepressant activity might be accounted for 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 results. D-phenylalanine is soaked up from the small intestine, following consumption, and carried to the liver through the portal blood circulation. A fraction of D-phenylalanine appears to be converted to L-phenylalanine. D-phenylalanine is dispersed to the different tissues of the body via the systemic flow. D-phenylalanine appears to cross the blood-brain barrier with less efficiency than L-phenylalanine. A portion of an ingested dosage of D-phenylalanine is excreted in the urine. [2]


Scientists think about phenylalanine to be an essential amino acid. This indicates that the body is not able to produce its own phenylalanine. Rather, an individual needs to get phenylalanine from dietary sources.

One 2020 study describes that since phenylalanine is a component of numerous natural proteins, high protein foods are excellent sources of this important amino acid.

Some examples of high protein foods include:.

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

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

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

Uses & effectiveness

Perhaps Effective for …

A skin condition called vitiligo. Taking L-phenylalanine by mouth in combination with UVA direct exposure or applying L-phenylalanine to the skin in mix with UVA direct exposure appears to be effective for dealing with vitiligo in adults and in kids.

Perhaps Ineffective for …

  • Attention deficit-hyperactivity condition (ADHD). Some research study suggests that clients 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 appear to have any result on ADHD signs.
  • Taking D-phenylalanine by mouth does not require to decrease discomfort.

Insufficient Evidence to Rate Effectiveness for …

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


1. Utilized to Produce Other Compounds

Like other amino acids, phenylalanine plays an important role in the production of other key compounds that are very important to health. For instance, it’s utilized to produce dopamine, a neurotransmitter that is involved in learning, memory and feeling.

The body likewise transforms phenylalanine to tyrosine, an amino acid that assists in the synthesis of proteins. It’s also associated with the production of norepinephrine and epinephrine, both of which are neurotransmitters released by the body in action to stressful situations.

A shortage in this crucial amino acid can cause a long list of symptoms, including confusion, anxiety, memory loss and low energy levels.

2. Might Reduce Signs of Depression

Among the leading L-phenylalanine benefits is its ability to improve mood and protect against anxiety. Although more research is required, some research studies have discovered that it might have powerful mood-boosting residential or commercial properties.

In fact, a study released in the Journal of Neural Transmission found that administering 75– 200 milligrams of DL-phenylalanine (DLPA) per day to 20 individuals improved a number of signs of depression, including total state of mind and agitation. Another research study found that integrating L-phenylalanine with L-deprenyl, a medication utilized to prevent the breakdown of dopamine, had an useful effect on signs of depression in 90 percent of outpatient participants.

3. Might Help in Treatment of Parkinson’s Disease

Parkinson’s disease is a condition that impacts the main nervous system, causing signs like tremblings, stiffness and sluggish movement. According to a study in the International Journal of General Medicine, Parkinson’s illness is also defined 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 disease, extra premium human trials need to be performed to determine how it may impact symptoms.

4. Eliminates Persistent Pain

Some research has actually found that phenylalanine might act as a natural painkiller to help reduce and manage chronic discomfort. One study even reported that it has actually been revealed to have analgesic residential or commercial properties in both human and animal trials, noting that it may help reduce discomfort caused by a range of conditions.

Another animal study showed that injecting horses with a combination of amino acids, including 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 aid with weight-loss? While more studies on the link in between L-phenylalanine and weight reduction are certainly needed, some emerging proof shows that phenylalanine could have a big impact when it concerns your waist.

A research study conducted by the Department of Gastroenterology at St. Bartholomew’s Medical facility in London really discovered that administering L-phenylalanine to 10 participants prior to meals reduced food intake and increased levels of cholecystokinin (CCK), a hormonal agent that promotes digestion and helps keep hunger under control. Another in vitro research study in the American Journal of Physiology had similar findings, keeping in mind that phenylalanine was able to increase secretion of CCK, which might potentially help in weight reduction. [5]

Research research study

Impact of co-trimoxazole on phenylalanine metabolism in man

An investigation was completed to examine impact of co-trimoxazole on phenylalanine food digestion. It was found that phenylalanine level remains high in the wake of taking co-trimoxazole. Proportion between serum-phenylalanine and tyrosine was likewise high. In a few patients, serum phenylalanine levels were marginally raised in fasting conditions. As a conclusion, it was proposed that the trimethoprim/sulfamethoxazole blend has a synergistic activity in upseting phenylalanine resistance.

An open study on phenylalanine in depressed clients

In a clinical 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 handled and there was no additional need of treatment for these patients. Mellow to direct reaction was seen in 4 patients. Four clients did not respond at all to phenylalanine. This examination shows that phenylalanine is significant in depressive patients.

Schizophrenia and obstruction 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 actually furnished aid for clients with positive symptoms [41] In any case, simply dopamine clog is not enough to reduce manifestations of schizophrenia in the method it is deemed those various neurotransmitters are in addition connected with pathophysiology of schizophrenia. Dopamine partiality for dopamine receptor is decreased by broadening adenosinergic transmission. Adenosine level might be broadened by discussion of allopurinol that is xanthine oxidase inhibitor, at last prompting antipsychotic and anxiolytic effects. Confirmation for this treatment has actually been represented in both case reports and little scientific trials. Different examinations demonstrate that allopurinol is important in those patients who are ineffectively responsive to existing treatment for schizophrenia. Nevertheless, additionally research study should be completed to find its viability and wellbeing as a basic treatment for schizophrenia. In any case, shows think about show 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 medical trial, phenylalanine was managed to 3 unique events. Dose of medication was 100 mg/kg phenylalanine. Eleven patients remained in very first gathering (prevented patients with tardive dyskinesia). Ten patients remained in second event (prevented client provided to neuroleptics yet without TD), 10 patients were in 3rd event (clients never ever provided to NLs). There was no important factual contrast amongst three gatherings. A relationship was found in between automated advancement and fasting, and phenylalanine stacking following 2 hours. Three TD patients showed surprisingly extensive increments in phenylalanine level in plasma. This assessment showed that variations from the norm in digestion of phenylalanine add to the enhancement and seriousness of TD in some NL-treated unipolar prevented patients. [6]

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

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

Phenylalanine can cause intellectual impairments, brain damage, seizures and other problems in individuals with PKU. Phenylalanine happens naturally in lots of protein-rich foods, such as milk, eggs and meat. Phenylalanine is also sold as a dietary supplement.

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

Federal guidelines require that any beverage or food which contains aspartame bear this warning: “Phenylketonurics: Contains phenylalanine.” This warning helps individuals with PKU prevent items that give phenylalanine.

If you do not have PKU, you probably do not require to fret about harmful health effects of phenylalanine– with specific essential exceptions. Aspartame in large dosages can trigger a quick boost in brain levels of phenylalanine. Because of this, usage products with aspartame meticulously 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 disorder, anxiety condition or other psychological 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, talk to your doctor. A blood test to figure out if you have PKU is offered and is now consistently done as part of newborn screening. [7]

How It Works?

How to Utilize It?

DLPA has actually been used in amounts ranging from 75– 1,500 mg each day. This substance can have effective results on mood and on the nerve system, and for that reason DLPA ought to be taken just under medical guidance. LPA has actually been used in quantities approximately 3.5 grams daily. For finest results, phenylalanine ought to be taken between meals, since the protein present in food can hinder the uptake of phenylalanine into the brain, possibly minimizing its impact.

Where to Find It?

LPA is discovered in a lot of foods which contain protein. DPA does not normally happen 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 substances can also be synthesized individually, but it is more pricey to do so. The combination supplement (DLPA) is frequently utilized because of the lower expense and due to the fact that both components exert various health-enhancing impacts.

Possible Shortages

Individuals whose diet plans are very low in protein might establish a deficiency of LPA, although this is thought to be extremely unusual. However, 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 allergic reactions, with signs such as:.

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

Side effects might include:

  • Heartburn
  • Tiredness
  • Queasiness
  • Irregularity
  • Dizziness
  • Headache
  • Stress and anxiety and hypomania (a milder kind of mania)
  • Sedation
  • Jitteriness and difficulty sleeping
  • Dosages higher than 5,000 milligrams a day can trigger nerve damage.

Risks. Individuals with specific conditions need to prevent using this supplement, including those with schizophrenia (tardive dyskinesia, a movement condition, may develop.) You also must avoid 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 use care in taking phenylalanine if you have:.

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

Preventative measures

Because of the capacity for negative effects and interactions with medications, you need to just take dietary supplements under the supervision of a well-informed health care company.

People with phenylketonuria (PKU), and females who are breastfeeding or are pregnant, need to not take phenylalanine supplements. Aspartame, discovered in sweetening agents such as Nutrasweet, gives phenylalanine. People with PKU should not utilize aspartame. If you are pregnant, ask your medical professional about using this sweetening agent.

DL-phenylalanine needs to not be used in individuals taking antipsychotic drugs, as it may trigger or get worse signs of tardive dyskinesia (TD). TDs are uncontrolled movements of the tongue, lips, face, trunk, and limbs that can occur in people taking antipsychotic drugs long term.

DL-phenylalanine might trigger signs of stress and anxiety, jitteriness, and hyperactivity in kids.

Doses higher than 5,000 mg a day may be harmful and can cause nerve damage. High amounts of DL-phenylalanine might trigger moderate adverse effects such as nausea, heartburn, and headaches.

Possible Interactions

If you are presently being treated with medication (particularly the following medications), you ought to not use phenylalanine without first talking to your healthcare service provider.

Monoamine Oxidase Inhibitors: Monoamine oxidase inhibitors (MAOIs) are an older class of antidepressants drugs that are seldom used now. They consist of phenelzine (Nardil), isocarboxazid (Marplan), and tranylcypromine sulfate (Parnate). Taking phenylalanine while taking MAOIs may cause a severe increase in high blood pressure (hypertensive crisis). This serious increase in blood pressure can cause a heart attack or stroke. People taking MAOIs should prevent foods and supplements containing phenylalanine.

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

Levodopa: A couple of case reports recommend that phenylalanine might lower the efficiency of levodopa (Sinemet), a medication used to treat Parkinson illness. Some researchers believe phenylalanine may disrupt the absorption of levodopa and worsen the person’s condition.

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

Antipsychotic or neuroleptic drugs: L-phenylalanine may aggravate 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 vital amino acid found in both plant and animal foods.

It may benefit the skin disorder vitiligo, however research on its results on anxiety, discomfort, and other conditions is restricted.

While it’s normally considered safe for healthy individuals, it’s important that those with phenylketonuria (PKU) keep their consumption low to avoid potentially hazardous negative effects.

If you notice any unfavorable side effects after taking a phenylalanine supplement or eating high protein foods, talk with your medical professional.

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


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