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Phenylalanine is an amino acid that develops proteins, neurotransmitters, and other essential molecules in your body. The body can’t produce phenylalanine, that makes it an essential amino acid we require to obtain from food.

Nutritional supplements can contain various kinds of phenylalanine with distinct systems and health results– we’ll dive into information about every one.


Phenylalanine molecule 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 only in a different way oriented in space.

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

D-phenylalanine is the artificial type made in the laboratory. Your body partly transforms it to the L-form or removes it via urine, but it also has some specific health effects gone over 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 first to be found. Marshall W. Nirenberg discovered that insertion of m-RNA made up of numerous uracil repeats into E. coli, the germs produced a brand-new protein, comprised exclusively of duplicated phenylalanine amino acids.


Phenylalanine can not be made by animals, which need 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 offer phenylpyruvate. This types is transaminated using glutamate as the nitrogen source to offer phenylalanine and α-ketoglutarate.

Other biological roles

L-phenylalanine can also 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 three are known as the catecholamines).

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

Lignin is stemmed 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 disorder are known as “phenylketonurics” and must avoid usage of phenylalanine. This dietary constraint also applies to pregnant females with hyperphenylalanine (high levels of phenylalanine in blood) due to the fact that they do not appropriately metabolize the amino acid phenylalanine. Persons struggling with PKU must monitor their consumption of protein to manage the buildup of phenylalanine as their bodies convert protein into its part amino acids.

A related problem is the substance present in numerous sugarless gums and mints, junk food, sugarless soft drinks (such as diet plan sodas including CocaCola No, Pepsi Max, some types of Lipton Tea, diet plan Nestea, Clear Splash flavored water), and a number of other low calorie food. The sweetening agent 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 problems phenylketonurics have with protein and the attendant develop of phenylalanine in the body also accompanies the consumption of aspartame, although to a lower degree. Appropriately, 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 carry ingredients panels that refer to the presence of ‘aspartame or E951’, [1] and they should be identified with a caution “Contains a source of phenylalanine”. These warnings are particularly put to assist people who experience PKU so that they can avoid such foods.

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

D- and DL-phenylalanine

D-phenylalanine (DPA) either as a single enantiomer or as a part of the racemic mixture is offered through standard organic synthesis. It does not participate in protein biosynthesis although it is discovered in proteins, in percentages, particularly aged proteins and food proteins that have been processed. The biological functions of D-amino acids remain uncertain. Some D-amino acids, such as D-phenylalanine, may have pharmacological activity.

DL-Phenylalanine is marketed as a nutritional supplement for its putative analgesic and antidepressant activities. The putative analgesic activity of DL-phenylalanine may 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 believed to be related to antidepressant results. D-phenylalanine is soaked up from the small intestine, following consumption, and transferred to the liver via the portal circulation. A portion of D-phenylalanine appears to be converted to L-phenylalanine. D-phenylalanine is dispersed to the various 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 a consumed dosage of D-phenylalanine is excreted in the urine. [2]


Researchers consider phenylalanine to be a vital amino acid. This implies that the human body is not able to produce its own phenylalanine. Rather, a person needs to get phenylalanine from dietary sources.

One 2020 research study explains that due to the fact that phenylalanine is a component of many natural proteins, high protein foods are great sources of this necessary 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 products and tempeh
  • plant-based “meat” items
  • plant algae
  • the sweetener aspartame

Foods and compounds that are low in phenylalanine include:.

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

Uses & effectiveness

Possibly Efficient for …

A skin problem called vitiligo. Taking L-phenylalanine by mouth in mix with UVA exposure or applying L-phenylalanine to the skin in mix with UVA direct exposure appears to be reliable for treating vitiligo in grownups and in kids.

Potentially Inefficient for …

  • Attention deficit-hyperactivity disorder (ADHD). Some research study recommends that clients with ADHD have lower levels of amino acids such as phenylalanine, so there was hope that providing phenylalanine might deal with ADHD. Nevertheless, taking phenylalanine by mouth does not seem to have any result on ADHD symptoms.
  • Taking D-phenylalanine by mouth does not require to minimize 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. However, it does not seem to improve acupuncture anesthesia for back pain.
  • Early research study 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 scientific research study carried out in the 1980s recommends L-phenylalanine or DL-phenylalanine might be beneficial for anxiety. Nevertheless, this research needs to be confirmed. Taking D-phenylalanine does not appear to improve signs of anxiety.
  • Numerous sclerosis. Early research recommends that using Cari Loder’s routine, which includes L-phenylalanine, lofepramine, and intramuscular vitamin B12 for 24 weeks, does not improve disability in individuals with numerous sclerosis.
  • Parkinson’s disease. Limited research study suggests taking one form of phenylalanine (D-phenylalanine) may decrease symptoms of Parkinson’s disease. Nevertheless, taking another form (DL-phenylalanine) does not seem to work.
  • Phenylalanine shortage. Early research recommends that taking phenylalanine by mouth may enhance phenylalanine shortage in kids with tyrosinemia.
  • Other conditions. [4]


1. Used to Produce Other Substances

Like other amino acids, phenylalanine plays an important function in the production of other crucial compounds that are necessary to health. For instance, it’s used to produce dopamine, a neurotransmitter that is associated with learning, memory and feeling.

The body likewise converts phenylalanine to tyrosine, an amino acid that assists in the synthesis of proteins. It’s likewise associated with the production of norepinephrine and epinephrine, both of which are neurotransmitters released by the body in reaction to demanding circumstances.

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

2. May Reduce Signs of Anxiety

One of the top L-phenylalanine benefits is its ability to enhance state of mind and safeguard versus anxiety. Although more research is needed, some studies have actually discovered that it might have effective 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) each day to 20 individuals enhanced several signs of depression, consisting of overall mood and agitation. Another research study discovered that integrating L-phenylalanine with L-deprenyl, a medication used to prevent the breakdown of dopamine, had a beneficial impact on signs of anxiety in 90 percent of outpatient individuals.

3. Could Aid in Treatment of Parkinson’s Disease

Parkinson’s disease is a condition that affects the central nervous system, causing signs like tremblings, tightness and slow motion. According to a research study in the International Journal of General Medication, Parkinson’s illness is also defined by an exhaustion of tyrosine, dopamine and norepinephrine, all of which are synthesized from phenylalanine.

Although one research study did discover that phenylalanine could be restorative in the treatment of Parkinson’s disease, extra high-quality human trials must be conducted to figure out how it might affect signs.

4. Eases Persistent Discomfort

Some research has found that phenylalanine might act as a natural pain reliever to help reduce and manage persistent pain. One study even reported that it has actually been revealed to have analgesic homes in both human and animal trials, noting that it might help reduce pain triggered by a range of conditions.

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

5. Might Promote Weight Reduction

Does L-phenylalanine assist with weight reduction? While more research studies on the link between L-phenylalanine and weight reduction are definitely required, some emerging proof shows that phenylalanine could have a huge impact when it concerns 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 consumption and increased levels of cholecystokinin (CCK), a hormonal agent that stimulates digestion and assists keep appetite under control. Another in vitro study in the American Journal of Physiology had comparable findings, keeping in mind that phenylalanine was able to increase secretion of CCK, which could potentially assist in weight loss. [5]

Research research study

Effect of co-trimoxazole on phenylalanine metabolism in man

An examination was finished to assess impact of co-trimoxazole on phenylalanine food digestion. It was discovered that phenylalanine level stays high in the wake of taking co-trimoxazole. Proportion between serum-phenylalanine and tyrosine was also high. In a couple of patients, serum phenylalanine levels were partially raised in fasting conditions. As a conclusion, it was proposed that the trimethoprim/sulfamethoxazole mix has a synergistic activity in offending phenylalanine resistance.

An open research study on phenylalanine in depressed clients

In a scientific trial, phenylalanine was controlled to 20 patients with gloom. Length of treatment was 20 days. Measurement of phenylalanine was 75– 200 mg/day. Towards the finish of treatment, 12 patients were dealt with and there was no further requirement of treatment for these patients. Mellow to direct reaction was seen in 4 patients. 4 clients did not respond at all to phenylalanine. This examination shows that phenylalanine is significant in depressive patients.

Schizophrenia and clog of dopaminergic neurotransmission

Phenylalanine is hydroxylated to tyrosine and tyrosine to dopa and dopa to dopamine. Dopamine has actually been involved for a long period of time in the pathophysiology of schizophrenia, and the run of the mill antipsychotics, by means of bar of dopaminergic neurotransmission, have actually provided assistance for clients with positive manifestations [41] In any case, just dopamine blockage is not sufficient to alleviate manifestations of schizophrenia in the method it is viewed as those various neurotransmitters are additionally related to pathophysiology of schizophrenia. Dopamine partiality for dopamine receptor is reduced by broadening adenosinergic transmission. Adenosine level might be broadened by presentation of allopurinol that is xanthine oxidase inhibitor, at last prompting antipsychotic and anxiolytic effects. Confirmation for this treatment has been accounted for in both case reports and little scientific trials. Various examinations show that allopurinol is valuable in those patients who are ineffectively receptive to existing treatment for schizophrenia. However, furthermore study should be finished to find its viability and wellness as a basic treatment for schizophrenia. In any case, exhibits think about show that allopurinol at 300 mg day by day is sufficient to lighten adverse effects of schizophrenia.

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

In a clinical trial, phenylalanine was managed to three distinct gatherings. Dosage of medication was 100 mg/kg phenylalanine. Eleven patients were in first event (discouraged clients with tardive dyskinesia). 10 patients were in second event (dissuaded client presented to neuroleptics yet without TD), 10 patients were in 3rd gathering (clients never presented to NLs). There was no crucial accurate contrast amongst 3 events. A relationship was discovered in between automated advancement and fasting, and phenylalanine stacking following 2 hours. 3 TD clients suggested remarkably extensive increments in phenylalanine level in plasma. This examination showed that variations from the norm in digestion of phenylalanine contribute to the improvement and seriousness of TD in some NL-treated unipolar dissuaded patients. [6]

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

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

Phenylalanine can cause intellectual disabilities, mental retardation, seizures and other problems in individuals with PKU. Phenylalanine occurs naturally in numerous protein-rich foods, such as milk, eggs and meat. Phenylalanine is likewise offered as a dietary supplement.

The sweetening agent aspartame (Equal, NutraSweet), which is contributed to numerous medications, diet plan foods and diet sodas, contains phenylalanine.

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

If you do not have PKU, you most likely do not require to fret about damaging health impacts of phenylalanine– with certain essential exceptions. Aspartame in big doses can cause a rapid boost in brain levels of phenylalanine. Because of this, use products with aspartame cautiously if you:.

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

Have the muscle motion condition tardive dyskinesia.

Have a sleep disorder, stress and anxiety disorder or other psychological health condition; phenylalanine might get worse sensations of stress and anxiety and jitteriness.

If you aren’t sure if phenylalanine or aspartame is a concern for you, speak with your medical professional. A blood test to identify 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 effective impacts on state of mind and on the nervous system, and therefore DLPA must be taken only under medical guidance. LPA has been utilized in amounts as much as 3.5 grams per day. For best outcomes, phenylalanine must be taken between meals, since the protein present in food can interfere with the uptake of phenylalanine into the brain, possibly reducing its result.

Where to Discover It?

LPA is discovered in a lot of foods which contain protein. DPA does not generally occur 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 two substances can also be synthesized separately, however it is more expensive to do so. The mix supplement (DLPA) is frequently utilized because of the lower expense and since both components put in different health-enhancing impacts.

Possible Shortages

People whose diets are extremely low in protein may develop a deficiency of LPA, although this is thought to be really unusual. Nevertheless, one does not always have to be deficient in LPA in order to benefit from a DLPA supplement. [8]

What are the threats of taking phenylalanine?

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

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

Negative effects might consist of:

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

Risks. People with specific conditions should prevent using this supplement, including those with schizophrenia (tardive dyskinesia, a movement disorder, might develop.) You also should 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
  • Trouble sleeping
  • Stress and anxiety or other psychiatric issues
  • Likewise, it is unknown whether this supplement is safe in females who are pregnant or breastfeeding. [9]

Preventative measures

Because of the capacity for adverse effects and interactions with medications, you need to just take dietary supplements under the supervision of an educated health care supplier.

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

DL-phenylalanine ought to not be used in individuals taking antipsychotic drugs, as it might cause or get worse signs of tardive dyskinesia (TD). TDs are uncontrolled motions of the tongue, lips, face, trunk, and limbs that can take place in individuals taking antipsychotic drugs long term.

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

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

Possible Interactions

If you are presently being treated with medication (specifically the following medications), you ought to not use phenylalanine without very first speaking with your health care 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 might trigger a serious boost in high blood pressure (hypertensive crisis). This severe increase in blood pressure can cause a heart attack or stroke. Individuals taking MAOIs must prevent foods and supplements consisting of phenylalanine.

Baclofen: Phenylalanine may reduce 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 may decrease the effectiveness of levodopa (Sinemet), a medication used to deal with Parkinson disease. Some scientists believe phenylalanine may hinder the absorption of levodopa and worsen the person’s condition.

Selegiline: L-phenylalanine and the selective MAO inhibitor selegiline (Eldepryl, Deprenyl) may strengthen the antidepressant effects of phenylalanine. They need to not be taken together.

Antipsychotic or neuroleptic drugs: L-phenylalanine may aggravate TD, an adverse effects of these neuroleptic drugs. These drugs include phenytoin (Dilantin), valproic acid (Depakene, Depakote), and carbamazepine (Tegretol), to name a few. [10]


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

It might benefit the skin condition vitiligo, but research study on its effects on depression, pain, and other conditions is limited.

While it’s normally thought about safe for healthy people, it is necessary that those with phenylketonuria (PKU) keep their intake low to avoid possibly harmful negative effects.

If you observe any unfavorable adverse effects after taking a phenylalanine supplement or consuming high protein foods, talk with your doctor.

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


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