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What Are the Benefits and Uses of Phenylalanine? How Much Do You Need?

L-phenylalanine is one of the crucial nutrients required to make dopamine and other hormones in your body. Dopamine is a hormone that makes you feel good. Plus, it plays a role in motor control. And it helps regulate memory and attention, among many other things. So it makes sense to prioritize getting enough L-phenylalanine. Without it, you’d never feel the satisfaction associated with completing a task or enjoying a great meal.

But it’s one of those amino acids that you may not be getting enough of regularly. And because your body doesn’t make it, you have to consume L-phenylalanine.

You can find the dopamine precursor phenylalanine in animal proteins and beans. Many people also take it in a supplement form for its ability to lift mood.

What Is Phenylalanine?

Phenylalanine is what’s known as an essential amino acid. Amino acids are organic molecules that your body links together to make proteins. Essential amino acids are those that your body needs to function properly but doesn’t make and can’t store for very long. You have to regularly ingest these essential amino acids. That means in order to get enough phenylalanine into your diet, you either need a phenylalanine supplement or you have to eat foods that are rich in this amino acid.

There are a few different forms of phenylalanine:

  • L-phenylalanine
    L-phenylalanine (sometimes shortened to LPA) is the natural form of phenylalanine. L-phenylalanine occurs naturally in some foods, including cow’s milk and sweet potatoes.
  • D-phenylalanine
    This form is lab-created and mirrors L-phenylalanine’s structure.
  • DL-phenylalanine
    DL-phenylalanine (also known as DLPA) combines both L-phenylalanine and D-phenylalanine.

L-phenylalanine is considered important for several bodily functions, including thyroid health and mood regulation. This is because your body converts L-phenylalanine to tyrosine, which is in turn used in the production of L-dopa which is then converted into dopamine, epinephrine, and norepinephrine. These neurotransmitters are known to help manage your mood.

Phenylalanine’s chemical structure indicates that it is non-polar. Phenylalanine is neither acidic nor basic— it is considered neutral.[1]https://pubchem.ncbi.nlm.nih.gov/compound/Phenylalanine

How to Pronounce Phenlyalanine

Phenylalanine can be tricky to say, but you pronounce it as “fen-ul-ALuh-neen.”

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Foods With Phenylalanine

The Dietary Reference Intakes (DRI; formerly known as Recommended Daily Allowances or RDA) for adult consumption of phenylalanine and tyrosine combined falls at about 33 mg daily per kilogram (2.2 pounds) of body weight.[2]https://www.nap.edu/read/11537/chapter/53#464

L-phenylalanine is found abundantly in many animal foods, but it is also in plant-based foods as well.

Some of the foods that are naturally high in L-phenylalanine[3]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5509543/:

  • Cow’s milk
  • Animal meats, like chicken, beef, and pork
  • Cheeses
  • Fish
  • Shellfish
  • Crustaceans
  • Eggs
  • Peanuts and peanut butter
  • Walnuts
  • Almonds
  • Beans
  • Legumes
  • Soybeans (edamame) and soy products like tofu
  • Bananas
  • Artichokes
  • Cilantro
  • Parsley
  • Watercress
  • Passionfruit

Is Phenylalanine The Same Thing As Aspartame?

Phenylalanine is also used as an ingredient in the popular artificial sweetener aspartame. Phenylalanine is therefore found in diet drinks, sodas, and gum. Many food products that include non-nutritive sweeteners like ice cream, drink mixes, or even cough drops may contain aspartame and therefore, phenylalanine.

That said, aspartame could possibly have some negative effects, so you shouldn’t seek out aspartame as a source of your phenylalanine requirement.

L-Phenylalanine vs. D-Phenylalanine vs. DL-Phenylalanine

D-phenylalanine (DPA) is the laboratory-created version of L-phenylalanine. While its structure is the mirror image (reverse) of L-phenylalanine, DPA doesn’t play the same role in the body as L-phenylalanine.

DPA is believed to help reduce pain. Its pain relief capabilities may stem from its ability to inhibit enkephalinase and interact with the body’s opioid receptors.[4]https://pubmed.ncbi.nlm.nih.gov/10998643/[5]https://pubmed.ncbi.nlm.nih.gov/33761014/

Enkephalinase is a peptide that can communicate pain signals within the brain.[6]https://www.sciencedirect.com/topics/neuroscience/enkephalin[7]https://pubmed.ncbi.nlm.nih.gov/18855623/

DL-Phenylalanine refers to the combination of equal parts DPA and LPA. This combo is thought to help with both pain relief and depression.[8]https://pubmed.ncbi.nlm.nih.gov/335027/

 

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L-Phenylalanine Benefits

L-phenylalanine is used for its potential to influence cognitive performance and help boost mood. Since it is believed that lower levels of dopamine can be associated with depression and Attention Deficit Hyperactivity Disorder (ADHD)[9]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2630359/[10]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4074363/, researchers are hopeful that increasing levels of phenylalanine can help treat them.

L-Phenylalanine And Depression

A few older studies looked at phenylalanine for the treatment of depression. And while they produced exciting results, not much further research followed.

In one small study, a majority of the study participants were able to discontinue treatment after just three weeks of DLPA supplementation.[11]https://pubmed.ncbi.nlm.nih.gov/335027/

And in another small study, 17 out of 23 depressed patients were able to completely resolve mood disturbances in just 13 days.[12]https://pubmed.ncbi.nlm.nih.gov/1173765/

Researchers also found overwhelming improvement in study participants when L-phenylalanine was combined with the medication L-deprenyl. Between 80-90% of patients reported beneficial effects.[13]https://link.springer.com/article/10.1007%2FBF01249880 Always check for drug and supplement interactions with your prescribing doctor or pharmacist.

Depression is a very real struggle, and support is easy to reach. If you’ve found this article because you are considering self-harm, call the National Suicide Prevention Lifeline at 1-800-273-8255 right now, or visit their website for free, 24/7 live chat support.

L-Phenylalanine For Focus

Since we know L-phenylalanine is a precursor to dopamine, and dopamine is important for memory and attention, it follows that phenylalanine may help with increasing focus and even possibly reduce ADHD symptoms.

One study suggested that DLPA did reduce ADHD symptoms, but the benefits didn’t seem to continue after three months of continuous use.[14]https://pubmed.ncbi.nlm.nih.gov/3903813/

Some doctors prescribe Adderall® or Ritalin® in addition to phenylalanine in order to help improve the performance of these ADHD medications.

What Else Is Phenylalanine Used For?

While L-phenylalanine is primarily considered a brain-loving supplement, researchers have also looked at L-phenylalanine for other potential uses as well.

Phenylalanine And Vitiligo

Vitiligo is a disease that attacks melanin in the skin. Since melanin is responsible for the pigment in skin tone, this disease results in pale, colorless spots on the skin. The exact cause and mechanism of vitiligo are not well understood. [15]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5362109/

Phenylalanine is required to make melanin.[16]https://www.sciencedirect.com/topics/medicine-and-dentistry/phenylalanine Therefore, phenylalanine supplementation along with light therapy has been used to treat vitiligo with promising results.[17]https://pubmed.ncbi.nlm.nih.gov/3885873/[18]https://pubmed.ncbi.nlm.nih.gov/8186511/[19]https://pubmed.ncbi.nlm.nih.gov/2583897/

Phenylalanine For Weight Loss

Anyone who frequents the gym knows that those who are serious about bodybuilding tout the benefits of amino acids. Plus, with L-phenylalanine’s reputation for supporting thyroid hormone production, it only makes sense that researchers began to look at L-phenylalanine for weight loss.

Studies have been encouraging, with L-phenylalanine appearing to help reduce appetite and belly fat.[20]https://pubmed.ncbi.nlm.nih.gov/18206190/[21]https://pubmed.ncbi.nlm.nih.gov/18206190/[22]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5833794/

Does Phenylalanine Increase Dopamine?

L-Phenylalanine is what’s known as a precursor to dopamine. That means that dopamine is formed by a metabolic reaction from phenylalanine. So you need phenylalanine in order to make dopamine.

It’s important to note that in order for your body to effectively utilize L-phenylalanine (and therefore proceed to dopamine generation), it also needs B vitamins, copper, iron, and vitamin C.

Studies indicate that phenylalanine possibly increases dopamine when given at just the right dose. When phenylalanine was given to rats, a dose of 200 mg per kg increased dopamine release. But a dose of 1000 mg per kg decreased dopamine.[23]https://www.sciencedirect.com/science/article/abs/pii/0304394088900183 More study is needed to determine exactly how phenylalanine impacts dopamine levels.

When Should I Take L-Phenylalanine?

It is generally believed that it’s best to take L-phenylalanine on an empty stomach. This will make it easier for L-phenylalanine to be used directly by the brain if it is not competing with other proteins found in foods.

L-Phenylalanine Dosage

There’s no one standard dosage for L-phenylalanine supplements. However, since researchers studying the effects of L-phenylalanine supplementation started patients on a 500 mg dose and kept increasing dosage by 500 mg until improvements were felt, many look to this method as a good way to determine L-phenylalanine’s efficacy for them.[24]https://pubmed.ncbi.nlm.nih.gov/6490415/

A commonly suggested dose for L-phenylalanine is 1000 to 1500 mg taken two to three times daily for nootropic benefit.

L-Phenylalanine Side Effects

While most people do not report adverse effects from phenylalanine, there are certain side effects to watch for.

Some reported side effects associated with higher doses of L-phenylalanine include:

Is Phenylalanine Safe?

L-phenylalanine is generally regarded as safe by the Food and Drug Administration (FDA).[25]https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=172.320

However, it shouldn’t be taken by women who are pregnant or nursing.

Also, it’s important to note that people with phenylketonuria (PKU) should not take L-phenylalanine supplements. PKU is an inherited disorder of phenylalanine metabolism. Phenylalanine is dangerous for people with PKU.

Likewise, it’s probably best for those with systemic lupus erythematosus (SLE or lupus) to avoid L-phenylalanine. While the research isn’t conclusive, emerging recommendations suggest that a diet low in L-phenylalanine may be beneficial for people with lupus.[26]https://www.frontiersin.org/articles/10.3389/fimmu.2020.01477/full[27]https://pubmed.ncbi.nlm.nih.gov/3898377/

Phenylalanine can also affect thyroid hormones, so if you have an overactive thyroid (hyperthyroid) it is best to stay away from L-phenylalanine.

Be sure to consult your doctor before taking L-phenylalanine. Do not take phenylalanine if you’re on medications like levodopa, baclofen, monoamine oxidase inhibitors (MAOIs), blood pressure medications, antidepressants, or neuroleptics.

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