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

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


    Phenylalanine molecule 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 only differently oriented in space.

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

    D-phenylalanine is the synthetic kind made in the lab. Your body partially transforms it to the L-form or eliminates it through urine, but it also has some specific health results gone over listed below.

    Supplements can include either form or a mixture of their equivalent quantities, referred to as DLPA (DL-phenylalanine). [1]


    The hereditary codon for phenylalanine was the very first to be discovered. Marshall W. Nirenberg found that insertion of m-RNA comprised of multiple uracil repeats into E. coli, the bacterium produced a new protein, comprised solely of duplicated 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 bacteria from prephenate, an intermediate on the shikimate pathway.

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

    Other biological functions

    L-phenylalanine can likewise be converted into L-tyrosine, another among 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 3 are known as the catecholamines).

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

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


    The congenital disease phenylketonuria (PKU) is the inability to metabolize phenylalanine. People with this condition are referred to as “phenylketonurics” and need to abstain from consumption of phenylalanine. This dietary constraint likewise applies to pregnant women with hyperphenylalanine (high levels of phenylalanine in blood) since they do not appropriately metabolize the amino acid phenylalanine. Persons suffering from PKU must monitor their intake of protein to manage the accumulation of phenylalanine as their bodies transform protein into its component amino acids.

    An associated concern is the substance present in lots of sugarless gums and mints, snack foods, sugarless sodas (such as diet plan sodas including CocaCola Absolutely no, Pepsi Max, some types of Lipton Tea, diet Nestea, Clear Splash flavored water), and a variety 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 offer phenylalanine, aspartic acid, and methanol (wood alcohol). The breakdown issues phenylketonurics have with protein and the attendant build up of phenylalanine in the body likewise occurs with the ingestion of aspartame, although to a lesser degree. Accordingly, all items in the U.S. and Canada that contain aspartame must be labeled: “Phenylketonurics: Contains phenylalanine.” In the UK, foods containing aspartame needs to carry ingredients panels that describe the existence of ‘aspartame or E951’, [1] and they must be labeled with a warning “Includes a source of phenylalanine”. These cautions are particularly placed to aid 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 discovered in people 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 conventional 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 unclear. 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 might be described by the possible blockage by D-phenylalanine of enkephalin degradation by the enzyme carboxypeptidase A. The system of DL-phenylalanine’s putative antidepressant activity may 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 believed to be associated with antidepressant effects. D-phenylalanine is absorbed from the small intestine, following consumption, and carried to the liver through the portal blood circulation. A fraction of D-phenylalanine seems transformed to L-phenylalanine. D-phenylalanine is dispersed to the various tissues of the body via the systemic blood 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]


    Scientists consider phenylalanine to be an essential amino acid. This suggests that the body is not able to produce its own phenylalanine. Instead, an individual needs to get phenylalanine from dietary sources.

    One 2020 study describes that because phenylalanine is a component of many natural proteins, high protein foods are excellent sources of this necessary 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” items
    • plant algae
    • the sweetener aspartame

    Foods and substances that are low in phenylalanine include:.

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

    Uses & & efficiency Possibly Effective for …

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

    Potentially Inadequate for …

    • Attention deficit-hyperactivity disorder (ADHD). Some research suggests that patients with ADHD have lower levels of amino acids such as phenylalanine, so there was hope that providing phenylalanine may deal with ADHD. However, taking phenylalanine by mouth does not seem to have any result on ADHD signs.
    • Taking D-phenylalanine by mouth does not require to reduce 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 recommends that taking a mix of D-phenylalanine, L-glutamine, and L-5-hydroxytryptophan for 40 days can improve some symptoms of alcohol withdrawal.
    • Minimal medical research study carried out in the 1980s suggests L-phenylalanine or DL-phenylalanine might be helpful for anxiety. Nevertheless, this research study requires to be validated. Taking D-phenylalanine does not appear to enhance signs of anxiety.
    • Multiple 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 disability in people with multiple sclerosis.
    • Parkinson’s illness. Limited research suggests taking one form of phenylalanine (D-phenylalanine) might decrease symptoms of Parkinson’s illness. Nevertheless, taking another form (DL-phenylalanine) does not appear to work.
    • Phenylalanine shortage. Early research recommends that taking phenylalanine by mouth may improve phenylalanine deficiency in children with tyrosinemia.
    • Other conditions. [4]


    1. Utilized to Produce Other Compounds

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

    The body also converts phenylalanine to tyrosine, an amino acid that aids in the synthesis of proteins. It’s also involved in the production of norepinephrine and epinephrine, both of which are neurotransmitters launched by the body in action to difficult situations.

    A deficiency in this essential amino acid can cause a long list of signs, including confusion, anxiety, amnesia and low energy levels.

    2. May Reduce Symptoms of Depression

    One of the leading L-phenylalanine advantages is its capability to enhance mood and safeguard versus anxiety. Although more research is needed, some research studies have actually discovered that it might have effective mood-boosting homes.

    In fact, a research study published in the Journal of Neural Transmission found that administering 75– 200 milligrams of DL-phenylalanine (DLPA) daily to 20 people enhanced numerous symptoms of depression, including overall state of mind and agitation. Another research study discovered that combining L-phenylalanine with L-deprenyl, a medication utilized to prevent the breakdown of dopamine, had an useful impact on symptoms of anxiety in 90 percent of outpatient participants.

    3. Might Aid in Treatment of Parkinson’s Disease

    Parkinson’s disease is a condition that affects the central nerve system, triggering symptoms like tremors, stiffness and sluggish motion. According to a study in the International Journal of General Medicine, Parkinson’s illness is also defined by a depletion of tyrosine, dopamine and norepinephrine, all of which are synthesized from phenylalanine.

    Although one study did discover that phenylalanine could be therapeutic in the treatment of Parkinson’s illness, additional premium human trials should be performed to determine how it may affect symptoms.

    4. Alleviates Chronic Pain

    Some research has discovered that phenylalanine could function as a natural painkiller to help in reducing and handle persistent pain. One study even reported that it has been revealed to have analgesic homes in both human and animal trials, noting that it may help in reducing discomfort triggered by a variety 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 chronic pain by preserving the activity of specific endorphins in the brain.

    5. May Promote Weight Reduction

    Does L-phenylalanine help with weight-loss? While more studies on the link in between L-phenylalanine and weight reduction are definitely needed, some emerging proof shows that phenylalanine could have a huge impact when it concerns your waistline.

    A research study carried out by the Department of Gastroenterology at St. Bartholomew’s Medical facility in London actually discovered that administering L-phenylalanine to 10 participants prior to meals minimized food consumption and increased levels of cholecystokinin (CCK), a hormonal agent that promotes food digestion and helps keep hunger under control. Another in vitro research study in the American Journal of Physiology had similar findings, noting that phenylalanine was able to increase secretion of CCK, which could possibly assist in weight-loss. [5]

    Research research study

    Impact of co-trimoxazole on phenylalanine metabolism in male

    An examination was finished to evaluate impact of co-trimoxazole on phenylalanine food digestion. It was discovered 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 upseting phenylalanine resistance.

    An open study on phenylalanine in depressed clients

    In a clinical 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 surface of treatment, 12 clients were dealt with and there was no more requirement of treatment for these patients. Mellow to direct response was seen in 4 clients. Four patients did not respond at all to phenylalanine. This examination reveals that phenylalanine is considerable in depressive clients.

    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 long period of time in the pathophysiology of schizophrenia, and the run of the mill antipsychotics, by means of bar of dopaminergic neurotransmission, have provided help for patients with positive symptoms [41] In any case, just dopamine clog is not adequate to ease 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 decreased by expanding adenosinergic transmission. Adenosine level might be expanded by presentation 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 clinical trials. Various examinations demonstrate that allopurinol is valuable in those clients who are ineffectively responsive to existing treatment for schizophrenia. Nonetheless, furthermore study ought to be finished to find its viability and wellbeing as a standard treatment for schizophrenia. In any case, shows consider show that allopurinol at 300 mg day by day suffices to lighten adverse effects of schizophrenia.

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

    In a scientific trial, phenylalanine was handled to 3 unique gatherings. Dosage of medication was 100 mg/kg phenylalanine. Eleven clients were in first gathering (dissuaded clients with tardive dyskinesia). Ten clients remained in second gathering (discouraged patient presented to neuroleptics yet without TD), 10 patients remained in third gathering (patients never ever presented to NLs). There was no important factual contrast amongst 3 events. A relationship was discovered in between automated advancement and fasting, and phenylalanine stacking following 2 hours. Three TD patients indicated surprisingly expansive increments in phenylalanine level in plasma. This evaluation showed that variations from the standard in food digestion of phenylalanine contribute to the enhancement and seriousness 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 many people. Nevertheless, for people who have the congenital disease phenylketonuria (PKU) or certain other health conditions phenylalanine can be a serious health concern.

    Phenylalanine can trigger intellectual specials needs, mental retardation, seizures and other problems in individuals with PKU. Phenylalanine happens naturally in numerous 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 added to many medications, diet foods and diet plan sodas, includes phenylalanine.

    Federal guidelines need that any beverage or food which contains aspartame bear this caution: “Phenylketonurics: Contains phenylalanine.” This caution assists individuals with PKU avoid products that give phenylalanine.

    If you don’t have PKU, you most likely don’t require to fret about hazardous health results of phenylalanine– with particular essential exceptions. Aspartame in large doses can cause a quick boost in brain levels of phenylalanine. Because of this, usage products with aspartame very carefully if you:.

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

    Have the muscle movement disorder tardive dyskinesia.

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

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

    How It Functions?

    How to Use It?

    DLPA has actually been utilized in amounts ranging from 75– 1,500 mg daily. This compound can have effective results on mood and on the nervous system, and for that reason DLPA needs to be taken just under medical supervision. LPA has actually been used in amounts approximately 3.5 grams per day. For finest outcomes, phenylalanine should be taken in between meals, due to the fact that the protein present in food can interfere with the uptake of phenylalanine into the brain, possibly reducing its result.

    Where to Find It?

    LPA is discovered in many foods that contain protein. DPA does not typically take place 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 substances can also be manufactured individually, but it is more expensive to do so. The mix supplement (DLPA) is often utilized because of the lower expense and due to the fact that both components apply various health-enhancing results.

    Possible Deficiencies

    Individuals whose diets are very low in protein might establish a deficiency of LPA, although this is thought to be extremely uncommon. Nevertheless, one does not necessarily need to be deficient in LPA in order to gain from a DLPA supplement. [8]

    What are the dangers of taking phenylalanine?

    Phenylalanine can trigger allergies, with symptoms such as:.

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

    Side effects may consist of:

    • Heartburn
    • Tiredness
    • Queasiness
    • Irregularity
    • Lightheadedness
    • Headache
    • Anxiety and hypomania (a milder type of mania)
    • Sedation
    • Jitteriness and problem sleeping
    • Doses higher than 5,000 milligrams a day can trigger nerve damage.

    Dangers. Individuals with certain conditions should prevent using this supplement, including those with schizophrenia (tardive dyskinesia, a movement disorder, might develop.) You likewise ought to 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:.

    • High blood pressure
    • Trouble sleeping
    • Stress and anxiety or other psychiatric problems
    • Also, it is unknown 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 must only take dietary supplements under the supervision of a knowledgeable health care provider.

    People 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 should not use aspartame. If you are pregnant, ask your doctor about using this sweetening agent.

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

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

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

    Possible Interactions

    If you are presently being treated with medication (particularly the following medications), you need to not utilize phenylalanine without very first speaking to your healthcare company.

    Monoamine Oxidase Inhibitors: Monoamine oxidase inhibitors (MAOIs) are an older class of antidepressants drugs that are rarely used now. They include phenelzine (Nardil), isocarboxazid (Marplan), and tranylcypromine sulfate (Parnate). Taking phenylalanine while taking MAOIs may cause a serious increase in blood pressure (hypertensive crisis). This extreme increase in high blood pressure can cause a cardiovascular disease or stroke. Individuals taking MAOIs need to avoid foods and supplements containing phenylalanine.

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

    Levodopa: A couple of case reports suggest that phenylalanine may lower the efficiency of levodopa (Sinemet), a medication utilized to treat Parkinson disease. Some scientists think phenylalanine might hinder the absorption of levodopa and intensify the person’s condition.

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

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


    Phenylalanine is an essential amino acid discovered in both plant and animal foods.

    It may benefit the skin disorder vitiligo, but research study on its impacts on anxiety, discomfort, and other conditions is limited.

    While it’s normally considered safe for healthy people, it is very important that those with phenylketonuria (PKU) keep their consumption low to prevent potentially hazardous adverse effects.

    If you discover any unfavorable negative 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 help figure out the very best course of treatment for you. [11]



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