Phenylalanine (also known as DL-phenylalanine or L-phenylalanine is an important neutral and nonpolar amino acid which is a key neurotransmitter precursor. Your body does not synthesize it endogenously. You can acquire it from your diet. You can find phenylalanine in foods rich in protein like eggs, beef, chicken and dairy. 

It helps treat vertigo and reduces pain. It also increases your catecholamine and dopamine levels, which enhance and energize your cognitive functions. 

Your body needs phenylalanine so it can produce tyrosine, which is also an amino acid. Nurotransmitters productions like norepinephrine, epinephrine and dopamine require tyrosine.  

Phenylalanine-Rich Foods 

High-protein foods are rich in phenylalanine. Dairy products (cheese and milk), meat products (beef and chicken), beans, nuts and eggs are just some of the good sources of phenylalanine. 

If you have phenylketonuria (decreased metabolism of phenylalanine), you better avoid these foods. 

Phenylalanine Supplements 

Phenylalanine has three different forms of supplements: D, DL and L-phenylalanine. 

  • D-Phenylalanine: This is a lab synthesized supplement that looks exactly like L-phenylalanine. Compared to L-phenylalanine, the D- form blocks the opioid-breaking enzyme and thus increases this supplement’s opioid and pain relieving effects. 
  • DL-Phenylalanine: This supplement is a combination of both the D- form and the L- form. 
  • L-Phenylalanine: This natural version supplement is normally found in foods and proteins in your body. 

Phenylalanine Health Benefits  

Phenylalanine can be a Parkinson’s disease marker 

Sadly, you can’t detect Parkinson’s disease by noninvasive methods. 

Almost half (49%) of patients with Parkinson’s disease have phenylalanine to blood tyrosine ratios of below 0.82, which is the healthy level. This lower ratio is probably a diagnostic of the disease. 

Parkinson’s will lead to loss of your dopamine neurons. However, you should not use phenylalanine supplementation to regenerate dopamine for Parkinson’s patients as it inhibits their L-dopa absorption. 

Phenylalanine gives short-term improvement in ADHD Symptoms 

Since low levels of dopamine is a factor in ADHD, phenylalanine supplementation can increase dopamine and thus help with the symptoms of ADHD.  

A study showed that ADHD patients who are taking DL-phenylalanine supplements have improved moods probably because of the increase in their dopamine synthesis. There was less restlessness or anger and more concentration. 

This beneficial effect of phenylalanine, however, didn’t last long. Just three months from the completion of the study, the patients developed a tolerance for phenylalanine. Even a higher dosage proved to be no longer effective.  

Phenylalanine alleviates symptoms of alcohol withdrawal 

If you are an alcoholic, and you start to detoxify, your body suffers from stress due to the withdrawal symptoms. Your body’s dopamine level and natural opioids will decrease because of this stress. 

Based on a test made on patients with withdrawal symptoms, there was a decrease in the psychiatric symptoms of patients who took D-phenylalanine supplements. 

Withdrawal stress was a common factor in all the test patients. The test showed that the 40 days D-phenylalanine treatment relieved that stress.  

Phenylalanine enhances acupuncture anesthesia’s effectiveness 

Carboxypeptidase are enzymes that destroy your body’s endogenous opioids. D-Phenylalanine inhibits carboxypeptidase and thus results in an increase in your natural opioids. 

In a clinical test, 18 patients took D-phenylalanine supplements before taking anesthesia for tooth extraction. Results showed that there was an increase of 35% to the acupuncture anesthesia effects compared to placebo.  

Phenylalanine increase levels of dopamine indirectly 

Dopamine is very important as it is needed by your body to perform various physiological processes like your brain’s reward system and pain perception. 

People with low dopamine levels, like those with Phenylketonuria, are at risk of suffering from severe intellectual inability. A test showed that patients with reduced levels of dopamine have executive functioning deficits.  

Phenylalanine is tyrosine’s direct precursor. Tyrosine is then converted by your body into dopamine.  

Although indirectly, phenylalanine increases your catecholamine neurotransmitters and this includes adrenaline, nonadrenaline and dopamine levels. 

In a clinical study, phenylalanine deficient participants took tyrosine supplementation. These participants have decreased stimulus reaction time. 

Water will not dissolve tyrosine, so even a direct supplementation of Tyrosine can’t efficiently increase dopamine in your body. Increasing the concentration of phenylalanine can better help your body produce more tyrosine and convert it to dopamine.   

Phenylalanine helps treat Vitiligo 

Vitiligo is a condition where your skin loses color. If you have this autoimmune disease, your immune system destroys your melanocytes (pigment making skin cells). 

Phenylalanine can help treat this skin condition. 

A study showed that more than 75% of patients undergoing UV therapy and vitiligo medication, improved a lot when they also started using oral and topical L-phenylalanine. 

L-phenylalanine has no side effects and is safe and useful in vitiligo treatment.  

Phenylalanine helps improve depression 

It has been proven that phenylalanine helps improve depression by increasing your drive and euphoria. 

They conducted a test with 20 depressed patients as subjects. These patients took 75mg to 200mg of D-Phenylalanine supplements per day for 20 days. Out of these 20, 12 showed improvement and discharged at the end of 20 days. These 12 didn’t even need any further or additional treatments. 

Out of the 8 who remained, 4 had moderate to mild antidepressant responses. The other 4 showed very little or no improvement at all. 

Similar rates of improvement were shown in other studies. These studies also showed that the D- and DL-phenylalanine supplements have no adverse effects even when the treatment was not successful. 

Phenylalanine can improve many of your depression symptoms like agitation, retardation and depressed mood. It can somewhat improve your sleep disturbance and anxiety. However, it has no effect on your compulsiveness and hypochondriasis (condition where a person believes he has a serious illness). 

Some depressed patients have low phenethylamine (phenylalanine metabolized product) in their urine. Only people with reduced phenethylamine can benefit from phenylalanine treatment as it does not affect those with high levels of phenethylamine.  

Users Review on Phenylalanine Supplements 

According to most users, phenylalanine has effects that are similar to coffee. It stimulates their tired minds and increases their energy when they feel slow. It also curbs food cravings and hunger. 

Users with depression state that they are more energetic with phenylalanine supplements. They are able to complete regular daily tasks as they feel energized. 

Most users reported that they didn’t experience dopamine effects that are stimulatory, like risk taking, which can be a dangerous side effect.   

 Side Effects of Phenylalanine 

Avoided by people with Phenylketonuria (PKU) 

In a test trial made on PKU patients, those who took phenylalanine supplements exhibited mood as well as attention impairments. The people conducting the study concluded that people with PKU should avoid phenylalanine in their diets forever. 

Aspartame, which is a common phenylalanine derivative, is a substitute for sugar in most foods. People with PKU should avoid aspartame as it also contains phenylalanine. They should also stay away from food with aspartame.  

Inhibits L-dopa (Parkinson’s drug)  

As stated above, phenylalanine supplements may interfere with Parkinson’s disease treatment. 

Parkinson’s disease has an “on-off” status or phenomenon. During this phenomenon, there are times where there is no transportation or absorption of levodopa. 

Patients can’t accomplish tasks or even walk on the “off” times and constantly need “on” treatment. 

When a study was made on 9 patients with Parkinson’s disease, it showed that the concentration of levodopa in their blood had a 29% decrease when they took meals reach in phenylalanine. There was also a 34-minute delay in absorption. 

Phenylalanine and levodopa have competing natures. Phenylalanine in high levels, reduces the movement of levodopa in your brain. This means that treatment’s effectiveness is also reduced. 

Levodopa is a strong medication so patients should not take it on empty stomachs.   

Nightmares and Anxiety Increase 

It is best to ask your physician before taking any supplements.  

A user experienced laughing attacks after using phenylalanine supplements. The user stated that the said experience was a nightmare, and it increased his anxiety.  

Blood Pressure Increase 

A study resulted in an extreme increase and decrease of blood pressure of the person being tested.  

Phenylalanine supplements may lead to an increase in your blood pressure, but it is normally not severe. 

Phenylalanine Supplementation Limitations 

There are contradictory results on supplementation of phenylalanine and one of them is tolerance. A human body can build a tolerance for the phenylalanine treatment.  

The treatment’s effectiveness and patients’ tolerance are probably not fully investigated as some of those who conducted the studies do not follow up with their patients after the completion of the test. 

SNPs and Genes that affect metabolism of Phehylalanine 

The gene responsible for converting phenylalanine to tyrosine is the Phendylalanine hydroxylase or PAH. Decreased memory and phenylketonuria is possible when the PAH gene is mutated. People with mutated SNP rs2037639 have verbal memory, which is lower than the general average. 

Currently, it is still not known how the metabolism of phenylalanine is affected by SNP. The belief is that, SNP regulates the PAH transcription, or it is linked to an unknown SNP. Any SNP rs2037639 change causes the levels of phenylalanine to alter. 

A trial made with PKU patients showed that they have a common mutation on their PAH gene’s SNPs R243Q and EX6-96.   

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