Phenylalanine

What is Phenylalanine?

Phenylalanine is an essential amino acid as the body cannot synthesise it and needs to be obtained from the diet.

Phenylalanine is a precursor to neurotransmitters dopamine, epinephrine and norepinephrine which are also known as catecholamines and follow the catecholamine pathway. Phenylalanine also slows down breakdown of the body’s natural opiates endorphins and enkephalines. These natural opiates have many roles including suppressing pain.

There are three aromatic amino acids that absorb ultraviolet light which includes tryptophan, phenylalanine, and tyrosine. All three aromatic amino acids absorb ultraviolet light with tryptophan absorbing most of the UV light.

Among the aromatic amino acids, only tyrosine has a side chain that can ionize.

Health Benefits of Phenylalanine

Helps balance mood

Phenylalanine is converted to tyrosine and follows the catecholamine pathway synthesising thyroid hormones and adrenal hormones or neurotransmitters dopamine, norepinephrine and epinephrine which contribute to overall mood balance. The L form of phenylalanine may help support mood imbalance, focus and attention. The neurotransmitter dopamine is also linked to motivation.

Tyrosine which can be synthesised from phenylalanine or obtained directly from food source converts to dopamine and needs sufficient amounts of biopterin, vitamin B3, copper and vitamin C for conversion. Dopamine beta hydroxylase needs ascorbic acid (vitamin C) in order to convert to norepinephrine which helps to improve mood and reduce symptoms of depression.

Phenylalanine which is needed in the synthesis of the catecholamine norepinephrine has been shown to act as an antidepressant. Phenylethylalanine is a natural antidepressant and a derivative of phenylalanine.

L-phenaylalanine converts to tyrosine which then converts to norepinephrine. Tyrosine follows the catecholamines pathway and converts to norepinephrine. Tyrosine can be used instead of phenylalanine and is readily abundant in most animal based protein food. Norepinehrine synthesis also needs other nutrients like magnesium and B12.

DL-phenylalanine has been used for chronic depression and may improve mood and this is directly from its conversion into tyrosine and then into norepinephrine. It is an important component of the catecholamines synthesis and also needed for dopamine production which helps with focus and uplifting mood. Tyrosine is also useful for anxiety.

It is also involved in endorphin levels in the brain which is needed to help boost positive mood.

Phenylalanine has been used for Parkinson’s disease which is known to be directly linked to a dopamine deficiency.

It has been used for various mental conditions which includes depression, bipolar disorder and hyperactivity or attention deficit-hyperactivity disorder (ADHD).

Phenylethylamine or PEA is another natural derivative of phenylalanine produced in the body which can cause feelings of euphoria, runners high, and even involved in the feeling of falling in love. This derivative acts like a natural amphetamine. PEA increases the release of dopamine and serotonin, two very important neurotransmitters associated with positive mood. It is also involved in the release of norepinephrine.

DL-phenylalanine needs vitamin B6 for healthy function of the nervous system. Amino acid metabolism needs active vitamin B6 (Pyridoxine HCI). Many of the B vitamins also help with mood with an imbalance or deficiency likely to cause low mood. They are also needed for cognitive functions such as memory and learning.

Depression is often linked to low levels of tryptophan or phenylalanine and or tyrosine. A deficiency of tyrosine or phenylalanine is often associated with a craving for foods high in sugar but also a strong craving foods high in tyrosine such as cheese, chocolate and other. This type of craving can be distinguished from low tryptophan where often there is a craving mostly for simple carbohydrates.

If there is unhealthy poor gut health and digestive issues such as low hydrochloric acid (HCL) production tyrosine is converted to tyramine.

Needed for neurotransmitters

Phenylalanine has a direct effect on brain chemistry as it is involved in the synthesis of various neurotransmitters that affect mood.

Phenylalanine is transformed into dopamine, norepinephrine, epinephrine and tyramine. Norepinephrine is an important neurotransmitter needed for concentration, alertness, attention, memory and learning.

Phenylethylamine (PEA) which is a neurotransmitter and a hormone is metabolized from phenylalanine and is associated with feelings of euphoria and released in the brain when falling in love.

Multiple Sclerosis (MS) is linked to neurotransmitter imbalance. A study has demonstrated that the intake of phenylalanine and other nutrients improved symptoms of MS. [R] [R]

Tyrosine amino acid has antidepressant effects as it is involved in the synthesis of dopamine which supports positive mood. Dopamine neurotransmitter can help reduce anxiety and provide bursts of energy.

Tyrosine needs folic acid, niacin, vitamin C and copper for the conversion of tyrosine into various vital chemicals and substances such as neurotransmitters, melanin (skin pigment that protects from UV rays).

Tyrosine also plays a role in the release of growth hormone. [R]

Tyrosine has also been used in the treatment of various neurological conditions such as Parkinson’s disease.

Supports fat metabolism

Tyrosine is needed for metabolism and studies have demonstrated that it can decrease body fat.

Although tyrosine may be easily obtained from the diet the body cannot convert tyrosine back to phenylalanine. Phenylalanine is needed for various bodily functions and is needed to synthesize phenythylamine (PEA) which is linked to feelings of euphoria and positive mood.

Helps with relieving pain

DL-phenylalanine can help reduce the breakdown of endorphins associated with reducing pain levels by inhibiting enzymes that would otherwise destroy these natural painkillers. People who are depressed or suffer from chronic pain have been found to have low levels of endorphins. Endorphins help relieve the sensation of pain.

DL-phenylalanine has been used to help reduce chronic pain and conditions linked to chronic pain such back pain, neck pain, rheumatoid arthritis, migraines, headaches, neuralgia and post-surgery pain. Phenylalanine has also been used for symptoms associated with pre-menstrual syndrome and menstrual cramps.

Tyrosine is also linked to estrogen (a hormone that has synergy with serotonin) and enkephalins (endogenous pain relievers).

Helps normalise blood pressure

Tyrosine can normalise blood pressure and has shown to have an adaptogenic effect. It can elevate blood pressure in people suffering with low blood pressure and lower it in those suffering with high blood pressure which has a normalising effect.

Supports thyroid hormone production

Phenylalanine can stimulate the thyroid to produce hormones needed for many bodily functions.

Thyroid hormones include thyroxine (T4) and tri-iodothyronine (T3). These hormones are iodinated derivatives of the amino acid tyrosine. They regulate growth, development and important metabolic functions.

Iodine is also important for thyroid function and combines with the amino acid tyrosine to form the thyroid hormones T4 (thyroxine) and T3 (triiodothyronine). Iodine is found concentrated mostly in the thyroid glands.

Deiodinase enzymes (DI’s) which rely on selenium are involved in the conversion of the thyroid prohormone T4 (thyroxin) into the active hormone T3 (triiodothyronine). These important enzymes also help convert T3 into T2. The activation of T3 by Deiodinase enzymes occur in the liver and brain.

Active form of T3 is important for growth and development of growing foetuses and infants. It is essential for the developing brain with deficiencies or impairment linked to birth defects and intellectual disabilities.

T3 also regulates important functions which includes metabolic rate, body temperature, protein metabolism, heart rate, lung function, producing sex hormones (testosterone and estrogen) neurotransmitter synthesis and involved with functions of the immune system.

Tyrosine has shown to increase libido in various animal studies which is likely due to its part in increasing sex hormones. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7592602/]

Stabilise blood sugar

Phenylalanine can stabilise blood sugar levels by supporting the adrenal glands and adrenal hormones.

Helps vitiligo
Phenylalanine has been used for vitiligo which is a skin disease characterized by patchy loss of skin color. Some studies show that the combination of phenylalanine and UV exposure markedly improved symptoms. [https://pubmed.ncbi.nlm.nih.gov/3885873/]

Helps with weight loss

Phenylethylamine (PEA) a derivative of phenylalanine is found mostly as weight loss supplements. It is linked to reduced appetite and may help with weightloss which may be helpful for people who overeat. Many depressive states are linked to binge eating which can lead to obesity.

Tyrosine is a mild appetite suppressant and is also used in weight loss.

Reduces alcohol withdrawal symptoms and may benefit addictive behaviour

Phenylalanine supplementation may be useful for alcohol withdrawal as it may balance mood and reduce withdrawal symptoms. Alcoholism is an addictive behaviour and may use up dopamine levels causing the alcoholic to reach out for another drink to soothe the mind. Many addictive behaviours are linked to dopamine receptors in the brain. The constant seeking of fulfilment found in addictive behaviour may use up dopamine levels causing a deficiency.

Replenshing dopamine levels and keeping the catecholamines neurotransmitters strong as well as having nutrients that support MAO production which help to deactivate these neurotransmitters so there isn’t too much circulating may help benefit all kinds of addictive behaviour.

Tyrosine is also used in programs designed to rehabilitee people with drug addiction.

Helps eliminate free radicals and toxins

Tyrosine can prevent damage to cells and tissues caused by chemicals, toxins, smoking, radiation and stress. It has some antioxidant effect and binds to free radicals for elimination.

Agonist / Synergist

Vitamins B2, B3, B6, B9, B11, C

Minerals Fe, Cu, Ca

Amino acids Methionine

Phenylalanine is a precursor for tyrosine (non essential amino acid)

Phenylalanine is a precursor for the monoamine neurotransmitters that follow the catecholamines path which include dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline)

Phenylalanine and tyrosine are precursors for the skin pigment melanin

Vitamin B2 (riboflavin) is needed by the body to convert vitamin B6 and vitamin B9 (folate) into forms it can use. Vitamin B2 also help absorption of vitmain B1 and B3. Vitamin B2 helps absorb minerals such as iron and zinc. Most of the B vitamins also work synergistically and needed in the right ratio.

Vitamin B9 (Folate) helps the body to use amino acids.

Vitamin B9 can regulate a healthy mood and overall wellbeing. This can have a positive impact and help with sleep. Deficiency of folate can lead to insomnia, irritability and depression.

Salicylic acid (B11) is synthesized from the amino acid phenylalanine.

Tyrosine is needed for dopamine synthesis and can be synthesised from phenylalanine.

Phenylalanine hydroxylase enzyme and cofactor nutrients are needed to convert phenylalanine to tyrosine

Tyrosine is converted to dopamine once it reaches the neurons and continues along the catecholamines pathway to synthesise norepinephrine.

Phenylalanine to Dopamine Synthesis

Vitamin B3 (NADH is the form of vitamin B3 needed), BH4 (tetrahydrobioptrin) a form of vitamin B9, Fe is needed to help convert phenylalanine to Tyrosine. This conversion requires phenylalanine hydroxylase enzyme. Tyrosine metabolism also needs NADH and BH4. Tyrosine needs these nutrients and vitamin B9 for conversion to L. Dopa which requires tyrosine hydroxylase enzyme. Tyrosine may also be directly ingested from food. Dopa decarboxylase enzyme or aromatic L-amino acid decarboxylase needs P5P (active form of vitamin B6) to convert L. Dopa to dopamine. The pathway continues to norepinephrine and epinephrine pathway of catecholamines.

DOPA decarboxylase (DDC) is needed for the synthesis of dopamine from L-DOPA and serotonin from L-5-hydroxytryptophan.

DDC catalyzes the conversion of aromatic amino acids tryptophan, phenylalanine and tyrosine into their corresponding amines dopamine, norepinephrine, epinephrine and serotonin.

Tyrosine needs both vitamin C and calcium for its utilisation.

L-phenylalanine is needed to convert to phenylethylamine by the enzyme aromatic L-amino acid decarboxylase through enzymatic decarboxylation. [R]

Taking carbohydrates with phenylalanine or tyrosine will help cross blood brain barrier

Tyrosine is more likely to be absorbed or cross brain barrier when taken on an empty stomach

MAO contains topa quinone. Topa is 2,4,5-trihydoxyphenylalanine (built on the amino acid phenylalanine) and copper is essential for its production

See Dopamine, Norepinephrine and Epinephrine for the catecholamines pathway conversions and cofactors

[ R] [R] [R]

Antagonists

Amino acids Branched chain amino acids (BCAAs; Leucine, isoleucine, and valine), tryptophan

Tryptophan inhibits tyrosine uptake in the brain

BCAAs (branched chain amino acids includes leucine, isoleucine and valine) compete with phenylalanine and tyrosine which can impact levels of neurotransmitters found in the brain that follow the catecholamines pathway which include dopamine, epinephrine and norepinephrine.

High BCAAs will also decrease thyroid hormones production by decreasing phenlylalanine and tyrosine absorption [R]

Higher levels of phenylalanine can inhibit increase of serotonin levels. Low or inhibited serotonin levels can cause carbohydrate craving. Low serotonin can cause insomnia and problems with mood [R]

High sugar and digestive issues with poor gut microbiome such as candida can cause tyrosine to convert to tyramine.

Impaired gut health (candida, parasites, low stomach acid etc), use of antibiotics and stress can cause tyrosine to convert to tyramine

Similar to tryptophan, other amino acids compete with tyrosine. In order to help tyrosine cross the blood brain barrier it is ideal to consume foods rich in tyrosine or its precursor away from foods that contain high amounts of competitive amino acids. When taking tyrosine supplement it may be helpful to take on an empty stomach or away from protein meals.

Caffeine may lower blood levels of tyrosine

Food Sources of Phenylalanine

Phenylalanine can be found in most high protein food and some plant based food source. It is more abundant in animal based food than in plant based food source. Animal based food source include beef, chicken, fish (herring), dairy products such as cheese, egg, cottage cheese and chocolate. Plant based food source include almonds, peanuts apple, avocado, baked beans, soya bean, soy proteins, banana beet, carrot, parsley, pineapple, spinach, tomato.

Mammalian breast milk contains phenylalanine.

Tyrosine which is derived from phenylalanine can also be found in food. Animal protein contain the highest amount of tyrosine.

Animal food source of tyrosine are similar to phenylalanine source and includes beef, pork, turkey, duck, chicken, fish, eggs, yoghurt, cottage cheese, cheese and milk.

Wild meat such as game and venison contain higher amounts of tyrosine.

Plant based tyrosine food source includes almonds, pumpkin seeds, sesame seeds, peanuts, soya bean, soy proteins, soya products, chocolate, apples, apricot, asparagus, avocado, baked beans, legumes, capsicum, carrots, spinach, alfalfa, beet, lettuce, parsley, watercress, leek, cucumber, banana, strawberries, cherries, fig and watermelon.

There is too little tyrosine in most plant based foods such as cereals, grains, fruits and vegetables.

Phenylethylamine can be found in chocolate and cheese but is unable to reach the brain due to breaking up quickly through digestion.

Aspartame contains phenylalanine. Aspartame is an artificial sweetener found as replacement to sugar in some sugar free sodas and foods as well as some medications. However this may not be a beneficial source of phenylalanine as various studies have linked high amounts to certain health problems.

Tyrosine etymology comes from the Greek word for cheese which is “tyros”.

Recommended Daily Allowance

The Recommended Dietary Intake (RDI) for phenylalanine is 14 milligrams per kilogram of body weight per day for adults from dietary intake for optimal functioning.

Children need more amino acids that adults as their body is still developing. The recommended daily amount for children over the age of three increases by 10% to 20% more than what is needed by adults. For infants the amount required increases by 150% more than what is needed by adults.

The requirements may change on individual basis and highly dependent on existing health.

Phenylalanine Supplementation

Phenylalanine is available as capsules, tablets or powders. This amino acid can be found in many full spectrum amino acid supplement.

It is available in three forms D-phenylalanine, L-phenylalanine and a combination of the D and L forms as DL-phenylalanine (DLPA). L-phenylalanine is the form that is natural and essential for the body. D-phenylalanine is the synthetic lab produced form.

The different forms contribute to specific functions and have different health benefits. The L form of phenylalanine may aid in maintaining regular mood and attention. Phenylalanine can be taken before meals and other amino acids should be avoided as they tend to compete with phenylalanine, especially BCAAs.

It is recommended to take phenylalanine after meals if suffering from hypertension (high blood pressure).

Phenylethylamine a natural derivative of phenylalanine is also available as a weight loss supplement.

PEA can be taken with an MAO-b inhibitor such as hordenine to feel the beneficial effects as without the inhibitor PEA is rapidly broken down during digestion. PEA induces feelings of euphoria and provides a burst of energy.

Taking single amino acid supplements are not always recommended and may be harmful for those with damaged liver or kidneys.

Deficiency Symptoms of Phenylalanine

Deficiency symptoms will be similar to dopamine deficiency as phenylalanine is needed for the synthesis of dopamine.

Deficiency of catecholamines (dopamine, norepinephrine and epinephrine) include:

Confusion
Lack of energy
Depression
Decreased alertness
Memory problems
Mood imbalance
Lack of appetite

Neurotransmitter imbalance is linked to mood problems as well as depression. Phenylalanine and tyrosine are the main precursors needed for the synthesis of dopamine and norepinephrine which are both implicated in depression when levels are low. These precursors also need various cofactors (enzymes, nutrients etc) for neurotransmitter production.

Precursors for neurotransmitter synthesis are important for overall functions of the brain which can contribute to general health and wellbeing. The synthesis rate of neurotransmitters will depend on the cofactors and precursors available in the diet.

Low tyrosine depression Vs. low tryptophan depression

Phenylalanine or tyrosine and tryptophan are amino acids linked to and are involved in the synthesis of some very important neurotransmitters that affect mood which is why a deficiency can lead to depression.

Tryptophan / serotonin type of depression

Low mood can be linked to either low tryptophan or low tyrosine and in many cases even both. Each type has various clues that can help pinpoint to which is causing the low mood. In low moods linked to tryptophan there is also a low production of serotonin, a key neurotransmitter that helps balance mood. When tryptophan is very low there is a craving for sweets and foods high in carbohydrates. People with this type of craving will find they are wanting to eat simple carbs more of the time such as white bread, pasta, rice and other simple carbs. Sleep is also a major clue to low mood associated with low tryptophan as it is linked to insomnia which may be corrected with supplementation. Tryptophan needs carbohydrates to be able to cross the blood brain barrier which explains the cravings for carbohydrates. Gut health is also important as most of the serotonin is produced in the gut. Foods high in pesticide aggravate gut health, impair digestion and reduce tryptophan levels. Women suffering from PMS or PMDD with mood swings and irritability during late luteal phase are likely to be low in serotonin and may notice a reduction of symptoms on oral supplementation of tryptophan.

Depression can be a balancing act between the two neurotransmitters serotonin which needs tryptophan and norepinephrine which needs tyrosine or phenylalanine. There needs to be a healthy balanced ratio of both neurotransmitters. In some cases taking high doses of tryptophan to increase serotonin can cause psychiatric and depressive symptoms to become worse when other neurotransmitters such as dopamine or norepinephrine may be deficient. If serotonin levels are low than tryptophan use may be very helpful and reduce associated symptoms of deficiency but if norepinephrine or dopamine is low these can be worse, in this case tyrosine or phenylalanine should help address symptoms associated with depression.

Tyrosine type of depression:

Low mood associated with low levels of tyrosine are quite different to low mood linked to a low level of tryptophan or serotonin in that the person is often craving foods particularly high in tyrosine which includes cheese, chocolate and other foods containing tyrosine. There is also a craving of high sugar or high simple carbohydrates food but with the addition of tyrosine based foods.

Like tryptophan there is also a link to gut health, in this case if digestive issues exist such as low hydrochloric acid to help digest food properly this will greatly reduce absorption and utilization of the nutrients necessary for balanced mood. Other digestive issues such as candidiasis can also hinder proper digestion and therefore utilization of tyrosine. In these cases tyrosine is converted to tyramine. Unlike tryptophan, tyrosine does not need carbohydrates to cross the blood brain barrier although some carbohydrates may help. However gut health is imperative where an unhealthy gut microbiome can cause tyrosine to convert to tyramine.

Like tryptophan, tyrosine also needs some carbohydrates to cross the blood brain barrier and is better to take on an empty stomach to avoid other amino acids from competing.

BCAAs can compete with phenylalanine or tyrosine and high amounts should be avoided when trying to address a deficiency. Tryptophan competes with phenylalanine or tyrosine for transport to the blood brain barrier.

Causes of deficiency:

Caffeine can lower blood levels of tyrosine which can exacerbate stress levels.
Impaired gut health (candida, parasites, low stomach acid etc)
Lack of dietary intake
Converting into too much tyramine

Excessive stress (uses up reserves of important neurotransmitters for stress such as noradrenaline

Tyramine causes the adrenal glands to work harder and uses up reserves of noradrenaline simultaneously depriving glands such as the thyroid glands of tyrosine. This can lead to a deficiency of the catecholamine neurotransmitters. Some of the deficiency symptoms that can occur if tyrosine cannot be converted to epinephrine include fatigue, pain, depression and apathy.

Symptoms of excess tyramine may include anxiety, exhaustion (from overstimulated adrenals), headaches, rapid heartbeat, high blood pressure, sweating, and nausea/vomiting. In severe cases, it may lead to a hypertensive crisis.

Toxicity Symptoms of Phenylalanine

The following are some of the symptoms linked to excess phenylalanine:

Excessive intake of phenylalanine or tyrosine may stimulate an already overstimulated nervous system.
Excess phenylalanine inhibit transport of other amino acids in the brain.
Lack of other amino acids needed in the brain (example tryptophan)
Brain damage (causes mental retardation / intellectual disability)
Seizures
Impaired central nervous system
Dopamine, norepinephrine and or epinephrine toxicity

Causes of phenylalanine toxicity include:

Excess supplementation or high dietary intake
Phenylketonuria (PKU)

Phenylketonuria (PKU) also known as Phenylalanine hydroxylase deficiency (PAH deficiency), is a rare inherited disorder characterised by accumulation of phenylalanine which can become life threatening if left untreated. People with PKU are unable to breakdown phenylalanine and therefore need to avoid phenylalanine and any food source of phenylalanine. People with PKU need to follow a strict diet usually restricted of protein based foods and any food source containing phenylalanine. People with PKU are unable to process phenylalanine as they lack the enzyme phenylalanine hydroxylase needed to convert phenylalanine into tyrosine. This is caused by mutations in the PAH gene.

If phenol food sensitivities exist then it may be good to avoid these as phenol can convert to phenylalanine which is harmful for people with PKU. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1388796/]

It is also essential that artificial sweeteners such as aspartame are avoided as many are a source of phenylalanine and will be dangerous for anyone with PKU.

Many high protein foods such as animal based food sources which includes meat are high in phenylalanine and should be avoided in those with PKU.

People with PKU may need to supplement with Tyrosine

The body can convert tyrosine to phenylalanine through a process called transamination. This process involves transferring the amino group from tyrosine to a molecule called alpha-ketoglutarate, which produces phenylalanine and another molecule called glutamate.

However, for people with PKU, this conversion process is impaired, and therefore, supplementation with tyrosine is necessary to ensure adequate levels of both phenylalanine and tyrosine in the body.

In the United States PKU accounts for 1 in every 15,000 births which is why the condition is tested for all infants. It is also tested in other countries such as Canada.

High levels of phenylalanine associated with PKU (phenylketonuria) can cause a range of symptoms, including:

Intellectual disability and developmental delays
Poor growth
Birth defects (from mother to baby in utero)
Microcephaly (small head size)
Behavioral and social problems
Skin rashes or eczema
Seizures or tremors
Musty odor in the breath, skin, and urine
Light skin, hair, and eyes
Hyperactivity
Tremors
Involuntary movements (arms and legs)

Excessive amounts of phenylalanine can cause damage to the central nervous system and brain, particularly in individuals with phenylketonuria.

There is some evidence to suggest that there may be a link between tyrosine and schizophrenia, although the exact nature of this link is still unclear. Some studies have suggested that people with schizophrenia may have altered levels of tyrosine and other amino acids in their blood, and that supplementing with tyrosine may have some benefits for improving cognitive function in people with the condition. However other studies have shown to make some psychiatric disorders worse.

Some research that suggests a possible link between tyrosine and certain cancers, including melanoma, but the evidence is not yet conclusive.

Neutral amino acids in large doses may help to lower levels of excess tyrosine and they include tryptophan, threonine, methionine, valine, isoleucine, leucine, and histidine which along with tyrosine and phenylalanine share the same transporter in the brain and in the intestinal mucosa.

Although caffeine lowers plasma levels of tyrosine it can also increase stress levels

Tyrosine is implicated in some forms of cancer where the amino acid may be used up more rapidly.

Although Phenylalanine is toxic in some health conditions and those with PKU is generally less toxic than vitamin C and by as much as ten times the amount of vitamin C.

It is recommended to avoid phenylalanine when taking MAO inhibitors (MAOIs). It is also important to avoid phenylalanine when taking tricyclic antidepressants as this type of drug can interfere with the breakdown of phenylalanine, leading to increased levels in the blood and potentially causing adverse effects.

Phenylalanine supplementation should be avoided during pregnancy and by people suffering from hypertension (high blood pressure) or PKU. To avoid blood pressure issues it is recommended to take phenylalanine supplements after meals instead of before meals. It may also be better to take earlier in the day as phenylalanine can be stimulating and is a cofactor for the excitatory neurotransmitter dopamine.

People with hyperthyroidism where thyroids are overactive or have Graves’ disease should avoid phenylalanine or tyrosine supplementation. Too much tyrosine can cause a higher production of thyroxine worsening symptoms in these conditions. If in doubt it is always recommended to speak with a health professional before starting any new supplemental regime.

People with lupus should avoid phenylalanine supplements and reduce foods high in phenylalanine such as meat and dairy products.