Table of Contents
Phenylalanine is a highly bio-available essential amino acid. Your body naturally converts L-Phenylalanine into the amino acid L-Tyrosine which is then converted into L-DOPA. Decarboxylation of L-DOPA results in synthesis of the neurotransmitter dopamine.[i]
Once converted into dopamine, the enzyme dopamine-beta-hydroxylase converts dopamine into the neurotransmitters norepinephrine (noradrenaline) and epinephrine (adrenaline). This triad of neurotransmitters are collectively referred to as “catecholamines”.
As a nootropic supplement, you may find several different forms of Phenylalanine available. L-Phenylalanine is the natural form found in proteins. D-Phenylalanine is a mirror image of L-Phenylalanine that is made in the lab. And DL-Phenylalanine is a combination of the two forms.[ii]
L-Phenylalanine can be a highly effective nootropic for boosting cognitive function because it boosts norepinephrine and dopamine production. Resulting in increased attention, motivation and working memory.
D-Phenylalanine (but not L-Phenylalanine) has been used to treat chronic pain although the clinical research in this area is sparse.
L-Phenylalanine also stimulates the production of thyroid hormones T3 (triiodothyronine) and T4 (thyroxine) which are crucial in maintaining both overall physical and cognitive health.
Phenylalanine helps:
- Cognitive Stress. L-Phenylalanine helps produce the catecholamine-triad of neurotransmitters dopamine, norepinephrine and epinephrine. Sleep deprivation and extreme stressors like heat and cold can deplete catecholamine levels. L-Phenylalanine restores them to preserve optimal cognition.[iii]
- Neurotransmitters. Phenylalanine is a necessary precursor for dopamine, norepinephrine and epinephrine. As your dopamine levels increase, you’re better able to concentrate, organize your thoughts, and stay productive.
- Attention Deficit Disorder (ADHD). L-Phenylalanine can be an effective treatment for some with ADHD symptoms. L-Phenylalanine works in synergy with pharmaceutical drugs like Ritalin and Adderall by boosting extracellular levels of dopamine. Helping these drugs be more effective. And mitigating side effects like crashes when the drug wears off.
Overview
L-Phenylalanine is an essential amino acid that you get from food or a supplement. The enzyme phenylalanine hydroxylase converts Phenylalanine in your liver into the amino acid L-Tyrosine.[iv]
Phenylalanine is found in protein-rich foods like soybeans, cheese, nuts, seeds, beef, lamb, chicken, pork, fish, eggs, dairy, beans, and whole grains. The artificial sweetener aspartame also contains Phenylalanine.
Your brain converts L-Tyrosine to L-DOPA which then produces the neurotransmitter dopamine. The unused dopamine is then further converted into the neurotransmitters norepinephrine (noradrenaline) and epinephrine (adrenaline). This triad of neurotransmitters are collectively referred to as “catecholamines”.
Many neurohackers prefer L-Phenylalanine over other catecholamine precursors because it supports neurotransmitter production without directly increasing neurotransmitter levels.
This last part is key because indiscriminately increasing neurotransmitters across the board can lead to imbalances and tolerance. Which can defeat the purpose of taking the nootropic in the first place.
For example, not enough epinephrine can decrease cognition. And too much norepinephrine can decrease attention, processing speed and executive function.[v]
L-Phenylalanine vs. D-Phenylalanine: What’s the Difference?
L-Phenylalanine is an essential amino acid which means you must get if from food. Or as a supplement. Your body cannot synthesize Phenylalanine on its own.
L-Phenylalanine (LPA) is converted into the amino acid L-Tyrosine in your liver. Once L-Tyrosine crosses the blood-brain barrier, it is converted into L-DOPA. Which is further converted into the neurotransmitters dopamine, norepinephrine (noradrenaline) and epinephrine (adrenaline).
D-Phenylalanine (DPA) is a synthetic version of, and mirror image of L-Phenylalanine created in the lab. DPA has a different mechanism of action in the body than LPA.
D-Phenylalanine (DPA) slows the action of the enzymes carboxypeptidase A or endorphinase and enkephalinase. These enzymes degrade endorphins. Slowing down these enzymes that reduce endorphins can help reduce pain.[vi]
DL-Phenylalanine is a 50/50 combination of L-Phenylalanine and D-Phenylalanine. By combining the two in theory you get the best of both an antidepressant and pain reducer.
How does L-Phenylalanine work in the Brain?
L-Phenylalanine boosts brain health and function in several ways. But two in particular stand out.
- L- Phenylalanine decreases depression. L-Phenylalanine is converted into L-Tyrosine which in turn is converted into L-DOPA in the brain. L-DOPA is then used to make the feel good neurotransmitter dopamine. So depression could be the result of not getting enough of the first amino acid (L-Phenylalanine) in the chain of events needed to produce dopamine.
In one study done in Germany, 20 depressed patients received from 75-200 mg per day of DL-Phenylalanine for 20 days. At the end of the trial 12 of the depressed patients could be discharged without any further treatment. 4 of the patients had a moderate decrease in depressive symptoms. And 4 patients showed no response.[vii]
- L-Phenylalanine boosts neurotransmitters. L-Phenylalanine turns into L-Tyrosine once taken as a supplement. It then converts into the neurotransmitter dopamine. Dopamine is used to control movement in your body, is fundamental to memory, attention and problem solving.
The unused dopamine can then convert into the neurotransmitters norepinephrine (noradrenaline) and epinephrine (adrenaline).
Norepinephrine is important for attentiveness, emotions, sleeping, dreaming and learning.
Epinephrine drives your ‘flight-or-flight’ response. It’s what prompts your reaction to dangerous circumstances, emergency situations, or in stressful situations or environments.
This balance in neurotransmitters is critical to the fully optimized, healthy brain. And why some neurohackers choose L-Phenylalanine to allow the body to make the neurotransmitters it needs. Instead of causing an imbalance by boosting one neurotransmitter over another.
A study in Venezuela investigated ADHD and autism, and the implications of amino acids on these neuropsychiatric disorders. 40 subjects affected by autism and 11 with ADHD along with 41 healthy subjects were included in this study.
The researchers found that those with ADHD had decreasing Phenylalanine and increasing glycine which disrupted their inhibitory neurotransmission system. Not enough phenylalanine and increasing lysine was present in those with autism.[viii]
Another study at Ohio State University looked at amino acids in 28 ADHD patients. And found all subjects with ADHD had significantly lower levels of the amino acids phenylalanine, tyrosine, tryptophan, histidine, and isoleucine. The researchers concluded each subject had a general deficit in amino acid transport, absorption or both.[ix]
How things go bad
As we get older, our brain and body chemistry and energy metabolism changes.
↓ Dopaminergic neurons are damaged or die
↓ Neurotransmitter levels decline
↓ Thyroid hormones decline
↑ Stress levels increase
↓ Working memory and mood decline
All of these changes are often attributed to aging. But could be a result of dietary and lifestyle choices. Unchecked, they could lead to neurodegenerative diseases like Parkinson’s, a drop in quality of life and depression.
L-Phenylalanine benefits
L-Phenylalanine can boost levels of the neurotransmitters dopamine, norepinephrine and epinephrine. And can help a sluggish thyroid produce more T4 and T3.
L-Phenylalanine can help boost cognition especially in stressful situations. It helps improve decision making, ‘flow state’ and creativity, cognitive flexibility, and working memory.
L-Phenylalanine converts into L-Tyrosine which then converts into L-DOPA to produce dopamine. L-DOPA is also used to make melanin in your body. This conversion process helps in the removal of neurotoxic quinones. And chelates heavy metals like mercury and lead which can accumulate in and damage neurons.
The dopamine that is not used by your brain is available to produce norepinephrine (noradrenaline) which is important for attentiveness, emotions, sleeping, dreaming and learning.
L-Phenylalanine may be an effective nootropic when stacked with ADHD/ADD meds like Ritalin or Adderall. It helps supply extracellular dopamine needed to improve the effectiveness of stimulants used to boost the uptake of dopamine in your brain.
How does L-Phenylalanine feel?
Keep in mind that L-Phenylalanine is a precursor to catecholamines. So if you’re not ‘low’ on dopamine, norepinephrine or epinephrine – you may not ‘feel’ anything.
Many neurohackers report a lift in mood, better focus, concentration, increased energy, and an overall sense of well-being. L-Phenylalanine can help readjust your motivation levels. It can help lower anxiety levels, especially social anxiety.
Supplementing with L-Phenylalanine can help bring your blood pressure down if its elevated from a stressful situation or environment. Take it before the stressful event if you can.
L-Phenylalanine helps buffer the effects of stimulants like caffeine or amphetamines. It helps potentiate and prolong the effects of Ritalin or Adderall, and reduces the crash.
If you’re into athletics or do manual work, you’ll find that supplementing with L-Phenylalanine before a workout or construction job can leave you feeling great afterwards. It may help mitigate many of the effects of acute stress caused by short-term stressors.
And L-Phenylalanine helps your body produce L-Tyrosine which helps to produce melanin, so you may find it easier to get a tan while at the beach.
L-Phenylalanine Clinical Research
Phenylalanine as an Antidepressant
Several studies have investigated using Phenylalanine for the treatment of depression. One study published in the journal Arzneimittel-Forschung looked at using DL-Phenylalanine in a small group of patients who failed to respond to popular antidepressants like MAOIs.
In this study, researchers worked with 23 patients diagnosed with depression and who had not responded to standard antidepressants. They were given 50 or 100 mg of Phenylalanine daily for 15 days. The researchers found that Phenylalanine completely improved mood in 17 of the patients. Within 13 days of the 15-day trial.[x]
Another study in the Journal of Neural Transmission studied DL-Phenylalanine use with 20 depressed patients. The subjects were given 75 – 200 mg/day of DL-phenylalanine for 20 days.
The study found that 8 patients completely recovered from depression. And another 4 experienced a significant improvement in mood. Another 4 patients saw mild to moderate improvements, and another 4 did not respond to treatment.
This study shows that Phenylalanine has considerable antidepressant properties. And is effective for the majority of people suffering from depression.[xi]
Phenylalanine for ADHD
Phenylalanine for ADHD seems at first glance as a natural solution for ADHD symptoms. It’s a precursor to the neurotransmitter dopamine which is targeted with stimulants like Ritalin and Adderall. But the very limited clinical evidence tell a different story for practical use.
In this double-blind crossover study, 19 patients with ADD were given DL-phenylalanine or a placebo for 2 weeks. 13 of the ADD patients experienced a significant improvement in ADD symptoms compared to the placebo. And patients saw an improvement in mood.
But the patients who did respond to DL-Phenylalanine lost all positive benefits within 3 months. And it’s interesting that a later study with ADHD patients using L-phenylalanine (not DL-Phenylalanine) produced no clinical benefit.[xii]
Another study from 1987 treated 11 hyperactive boys for 2 weeks with D-Phenylalanine. There was no significant improvement or deterioration in behavior.[xiii]
There is a modern school of thought that there are several different types of ADD and ADHD. And the symptoms are caused by malfunctions in different parts of the brain depending on the ‘type’ of ADHD.
The bottom line is some dealing with ADHD may benefit from supplementing with Phenylalanine. And that DL-Phenylalanine may be the best option. Try it and see if it works for you.
L-Phenylalanine Recommended Dosage
L-Phenylalanine suggested dosage for cognitive benefit is 500 mg up to 3-times per day.
You may find your body responds to smaller doses. Or even more if your stacking it with stimulants like ADHD meds. Listen to your body and see how you react.
Since L-Phenylalanine is an amino acid, for best absorption and so it’s not competing with other amino acids, take it at least an hour before food. L-Phenylalanine works best on an empty stomach.
And take L-Phenylalanine with Vitamin B6 and Vitamin C to further maximize absorption. And give your body what it needs to produce the neurotransmitters dopamine, norepinephrine and epinephrine.
L-Phenylalanine is also needed along with L-Tyrosine to synthesize the CoQ10 needed to create fuel within your brain’s mitochondria.
L-Phenylalanine Side Effects
L-Phenylalanine quickly turns into the non-essential amino acid L-Tyrosine once you take it. So is considered non-toxic and very safe. Most neurohackers don’t have any negative side effects.
Important Caution: People with phenylketonuria (PKU), and women who are breastfeeding or are pregnant, should not take phenylalanine supplements. PKU is an inherited condition where excess phenylalanine can build up in your body. Aspartame, found in artificial sweeteners such as NutraSweet, is a source of phenylalanine. People with PKU should not use aspartame. If you are pregnant, ask your doctor about using this artificial sweetener.[xiv]
At higher doses there are reports of stomach issues and migraines. Experts say that L-Phenylalanine is toxic in doses above 5000 mg. And higher doses will not give you any added benefit.
If you try recommended doses of L-Phenylalanine and do not feel any benefit, then this nootropic may not be right for you. You could try L-Tyrosine or NALT instead.
L-Phenylalanine can increase your thyroid hormones. So if you’re hyperthyroid you shouldn’t use L-Phenylalanine.
And if you’re taking MAO inhibitors (MAOI’s) like selegiline, Azilect, Marplan or Nardil you should not use L-Phenylalanine. MAOI’s work in your brain and affect neurotransmitters. So using L-Phenylalanine in combination with MAOI’s could throw off the delicate balance of neurotransmitters needed for optimal brain health and cognition. And taking L-Phenylalanine with MAOI’s could cause a severe increase in blood pressure which could lead to a heart attack or stroke.
Other sides effects which can accompany unusually high doses of phenylalanine can include anxiety, rapid heart beat, restlessness, heart palpitations or high blood pressure. If you are dealing with or on medication for high blood pressure you should not use L-Phenylalanine.
Type of Phenylalanine to buy
L-Phenylalanine is available in powder, capsule and tablet form. Capsules and tablets are usually 500 mg.
Phenylalanine is also available as D-Phenylalanine and the 50/50 combined form of DL-Phenylalanine. You may find one form works better for you than another.
Ensure you read labels carefully, and stick with manufacturers who follow Good Manufacturing Practices (GMP). And are GMP-Certified.
Nootropics Expert Recommendation
L-Phenylalanine 500 mg up to 3-times per day
I recommend using L-Phenylalanine as a nootropic supplement.
Your body does synthesize some L-Tyrosine from phenylalanine which comes from high-protein foods like chicken, fish, almonds, avocados and bananas.
But most of us don’t get enough L-Phenylalanine from our diet. So supplementation will help. And L-Phenylalanine is a highly bioavailable, natural form of this amino acid. So you should feel its effects faster.
L-Phenylalanine is helpful for most neurohackers to combat stress and sleep deprivation. It’ll boost dopamine, norepinephrine and epinephrine levels.
It’s particularly helpful if you take L-Phenylalanine prior to a stressful situation, workout or physically demanding job.
L-Phenylalanine could be helpful to those dealing with ADHD/ADD. It’s a great compliment to stack with stimulant meds like Ritalin or Adderall. L-Phenylalanine will provide the dopamine your brain needs. It will help smooth out and prolong the effects of stimulant meds. And help prevent the associated crash when they wear off.
You can safely use up to 1,500 mg per day when stacking with ADHD meds. But dosed throughout your day.
Join The Discussion - 135 comments
Sean
August 27, 2021
Hi David,
I am THRILLED to have found your site.
I use it often. Most comprehensive and best source of nootropic information I’ve found so thanks for this!!
Now my question.
Phenylalanine you said is derived from aspartame?
Aspartame is known to potentially cause Alzheimer’s and bring about other possible toxic and or damaging events in the body.
Did I misread or am I lacking understanding here?
I recently added the DL type, 750 mg once a day.
Seems useful in my stack of
Lions mane, PQQ, Alpha GPC, lithium Oratate, NALT, Liquid B vitamins, Boswellia, K2 + vit D and Cod Liver oil.
Also curious about your opinion on my stack.
To much, to many?
Thank you for any suggestions!
Sincerely
Sean J
David Tomen
August 27, 2021
Sean, that’s not what I said. The artificial sweetener aspartame contains Phenylalanine. It’s not derived from aspartame.
If this stack works for you that is what counts. Not my opinion. But I don’t see a reason to supplement with DL-Phenylalanine and NALT because they are both precursors for the synthesis or dopamine.
And why are you using Cod Liver Oil?
Mich
August 14, 2021
I just bought l-tyrosine today because dlpa was not available near me. I still plan on using dlpa in my stack. How do you suggest I stack l-tyrosine, dlpa, and SAM-E? I suffer from S.A.D. and I want to be ready for the end of Summer. I’ve been relatively okay (aside from feeling suicidal 2 weeks ago), Summer has had me even-keeled overall. I am afraid of what’s gonna happen when Fall begins, so I’m trying to figure out a good stack before that happens
David Tomen
August 15, 2021
Mich, I need to write an article about the Best Nootropics for Seasonal Effective Disorder (SAD). But for now, L-Tyrosine 500 mg 2 or 3-times per day may help.
You also need Vitamin D3 5,000 IU per day, a high quality B-Complex like this one: https://amzn.to/3iLIMGk, and several studies have shown that St. John’s wort helps including SKW with light therapy (https://pubmed.ncbi.nlm.nih.gov/10216809/). But rather that using a SJW with hypericin studies have shown Perika (hyperforin) to be more effective and with less problems (https://amzn.to/3CLRdtj).
finally, I suggest doing a search of this website for the keyword “SAD” and/or “Seasonal Effective Disorder” and see if I missed anything.
Mich
August 15, 2021
I look forward to your future article. I am trying to understand everything I can as I am just starting. I also see that timing plays a big role in taking any of these supplements. I am trying to figure out a good schedule to take these since I hear elevating dopamine depletes serotonin(?). Then there’s the confusing part about which is better, L-tyro or dlpa? I will follow your advice and read more about SAD on this site and learn as much as I can. Hopefully, the darker months (I live in the PNW) will be a better and safer rider than in the previous years.
David Tomen
August 16, 2021
Mich, DLPA is 3 steps away from making dopamine and L-Tyrosine is 2 steps away. One is not “better” than the other. Most use L-Tyrosine because it makes dopamine quicker. But some prefer one over the other. I suggest that understand the difference between the two by reading my reviews on each thoroughly. The decide if you want to try one or the other or decide to use both which I do not think necessary.
Keep in mind the half-life on both is only 2 – 3 hrs. So the Tyrosine you use at 8 AM is gone by noon. And when taken at noon is gone by around 4 PM.
Excess dopamine depletes serotonin. And vice versa. So if you are increasing dopamine during the day it is wise to use 500 mg L-Tryptophan before bed to increase serotonin and keep them in balance.
Do you due diligence now and I’m sure the darker months will not be so dark anymore.
Elizabeth
July 31, 2021
Hi David,
I watched your video on Phenylalanine, and it was very informative. I have a question about stacking. This stuff naturally raises serotonin and other chemicals, right? What if I take it with L-theanine or Tryptophan, that increase some of those chemicals too. Is that a bad mix up, should I stick to one? My issues are anxiety and insomnia.
Thanks!
David Tomen
August 2, 2021
Elizabeth, Phenylalanine is a precursor to the synthesis of L-Tyrosine which then goes on make L-DOPA and then dopamine. So Phenylalanine increases dopamine. Which means you need to be careful about stacking it with any nootropic that acts like an MAOI and stacking it L-Tyrosine or L-DOPA. Excess dopamine can produce some nasty side effects.
Sonya H.
July 1, 2021
I have no idea why, but D-phenylalanine makes me incredibly sleepy. I take it with b vitamins and do a normal workout in an attempt to increase my PEA levels, but instead I feel a wash of drowsiness like I’ve taken a tranquilizer. The same effect happens if I take it all by itself, 500mg or 1g, with or without exercise. Any idea why this might be happening to me?
David Tomen
July 3, 2021
Sonya, scroll back up to the section called, “L-Phenylalanine vs. D-Phenylalanine: What’s the Difference?” You are using the synthetic version of this supplement and may have better luck with that natural L-Phenylalanine.
If that doesn’t work you may have a condition called “phenylketonuria (PKU)” and if you do then you should be using phenylalanine supplements. PKU is an inherited condition where excess phenylalanine can build up in your body.
Milan
March 6, 2022
Just noticed small mistake and it’s important to correct it to prevent possible side effects. Basically, David said everything correctly, but missed a word “NOT” in the following sentence – “phenylketonuria (PKU)” and if you do then you should be using -> you should NOT be using phenylalanine!
Please, correct me if I’m wrong.
FYI, I’m having ADHD and this article is great as it provided me with new information I was not aware of.
Many thanks, David!
David Tomen
March 7, 2022
Milan, I think you read that wrong. I definitely said “People with phenylketonuria (PKU), and women who are breastfeeding or are pregnant, should not take phenylalanine supplements.”
Tarun
September 12, 2022
This is what you said David:
“If that doesn’t work you may have a condition called “phenylketonuria (PKU)” and if you do then you should be using phenylalanine supplements. PKU is an inherited condition where excess phenylalanine can build up in your body.”
It’s in the comment you made above.
David Tomen
September 13, 2022
Tarun, you are correct and that is my mistake. I should have said “not” be using … Thank you for the correction.
Mendel
June 18, 2021
Hi David,
I have ADD, I recently quit nicotine and have been feeling depressed, I saw someone recommend phenylalanine, tyrosine and L-dopa after quitting nicotine and I’m now considering using these to see what it does for my depression, but I’m also very curious to see what it does for my ADD symptoms.
Should I experiment with all 3 together? (I’ve seen you’ve been cautionary about L-dopa in comments) What would you recommend?
Thanks for your time!
David Tomen
June 19, 2021
Mendel, Phenylalanine, Tyrosine and L-DOPA are all precursors to the synthesis of dopamine. L-DOPA is an immediate precursor. Tyrosine goes on to make L-DOPA which then makes dopamine. And Phenylalanine makes tyrosine which makes L-DOPA which then makes dopamine.
If you try using all three you’ll likely end up with excess dopamine which is not good.
The other thing is Nicotine binds to nicotinic acetylcholine receptors in your brain. Boosting the release of acetylcholine (ACh), dopamine, serotonin, and glutamate. So just boosting dopamine is not going to replace quitting nicotine.
Other nootropics that also affect nicotinic acetylcholine receptors include Rosemary, Nefiracetam, Phosphatidylserine (PS), and Noopept. I suggest looking up each of these here on Nootropics Expert and get familiar with them.
For ADD you do need L-Tyrosine. But you also need the rest of the stack you’ll find in the yellow box near the top of this page: https://nootropicsexpert.com/best-nootropics-for-adhd-add/
Casey
May 21, 2021
As a medicated adult ADD patient, I feel like phenylalanine is turning the lights back on..truly! I pray it doesn’t cease working as I will be so disappointed. I can often skip my pm does of meds which I haven’t done in years. Out of the dozens of supplements I’ve used, Phenylalanine feels like the missing piece to the puzzle. I can’t believe it! Praise God for this supplement!
A.M
March 24, 2021
Hi there. Much appreciate yr time to reply here. I’ve been trying out a few nootropics for mood as g get swings and depression. Am in menopause. L phenylalanine alone didn’t do much but caused higher libido , and sadly constipation. L tyro alone seemed to make me more weepy? Now trying dl phenylalanine. Good lift but again constipation? Amy ideas why or what I could take beyond laxatives to help body absorb the dl phena? Thank you.
David Tomen
March 24, 2021
AM, you are doing everything to boost dopamine. But what if it’s not dopamine deficiency that is causing your depression?
What if it’s a serotonin deficiency, or acetylcholine, or GABA, or …
I suggest you try boosting each of those neurotransmitters one at a time and see what happens.
Tees
February 7, 2021
Hello! Recently I have started taking DLPA , is it safe to take this alongside Rhodiola Rosea and Acetyl L Carnitine ? ( would adding the Rhodiola provide any additional benefit? ) Thank-you!!
David Tomen
February 7, 2021
Tees, Rhodiola Rosea may potentiate the effects of DLPA because Rhodiola influences norepinephrine. The could be a benefit or it could work against you depending on how you react to that combination.