Phenylalanine – Side Effects, Definition, Facts, Functions, Uses, Health Benefits, Food Sources

Phenylalanine – Side Effects, Definition, Facts, Functions, Uses, Health Benefits, Food Sources:


It is an essential amino acid (a block of proteins in the body), which means that the body needs it for health, but it can not produce it itself; instead, the body must obtain it from food. It was found by Schulze and Barbieri in 1879, in the seedlings of Lupinus Zuteus.

Phenylalanine (abbreviated as Phe or F) is found in three forms: L-phenylalanine, the natural form found in proteins; D-phenylalanine (a reproduction of L-Phe in the laboratory); DL-Phe, a combination of the two forms.

Uses and functions

This essential amino acid is converted by the body into dopamine, noradrenaline, and adrenaline, three chemicals that play a major role in the transmission of nerve impulses between the brain and the cells receptive to these impulses. Supplements containing this amino acid can make a person feel happier, reduce hunger sensation, and increase attention.

It was also proven that it treats chronic pain and improves memory and concentration. DLPA has positive effects in terms of sensitivity to pain and mental state. The genetic disorder called phenylketonuria is the body’s inability to metabolize Phe. PKU can lead to irreversible mental retardation if not treated in the first few days after birth.

Health Benefits

Prevents depression and anxiety

A deficiency of this essential amino acid is often obvious when the person shows signs of depression and fatigue. This may occur because the body uses Phe to produce the tyrosine amino acid, which in turn produces dopamine, noradrenaline, and other chemicals that adjust mood and adrenaline.

Thus, many believe that one of the most important beneficial effects of this amino acid is its ability to regulate mood and help fight depression.

Food sources of phenylalanine

This essential amino acid is found in foods containing proteins, such as meat, dairy, bananas, soy products, hazelnuts, pecans, almonds, Brazil nuts, chia seeds, flax seeds, sunflower seeds, pumpkin seeds, sesame seeds, white beans, red kidney beans, mung beans, adzuki beans, lentils, chickpeas, grains (such as – millet, oats, oat bran, quinoa, amaranth, wheat, wheat bran). Aspartame (artificial sweetener) is also rich in this amino acid.


Vitiligo occurs in about 1 percent of the world’s and the United States’ population.

Preliminary studies suggest that ingesting supplements containing this amino acid (topical and oral) strengthens the effect of UVA radiation for patients with vitiligo.

Vitiligo is a condition that causes the loss of skin color in blotches. Some patients can also lose color inside their mouths. Globally about 1 percent of people are affected by this disease.

Parkinson disease

Parkinson’s disease is one of the most frequent neurodegenerative disorders, affecting about 1 percent of individuals older than 60 years and leads to progressive deterioration of motor function because of the loss of dopamine-producing brain cells.

Sometimes it is genetic; however, in most cases, it does not seem to run in families. One animal study suggests that this amino acid may improve walking disabilities, rigidity, and speech difficulties.

Side Effects of Phenylalanine

Due to the potential side effects and interactions with medications, dietary supplements should be taken only under a doctor’s supervision.

People suffering from phenylketonuria and pregnant or nursing women should not take supplements containing this amino acid. Also, people with PKU must avoid using products with aspartame, as it contains this amino acid. Pregnant women should ask their doctor about using this artificial sweetener.

Moreover, supplements with this amino acid should not be used by individuals taking antipsychotic drugs, as it can cause or worsen symptoms of tardive dyskinesia. TD is manifested by involuntary movements of the tongue, lips, face, torso, and limbs, and can occur in people taking the antipsychotic medication in the long-term.

Lastly, this amino acid may cause symptoms of anxiety, nervousness, and hyperactivity in children. Large amounts of this amino acid can cause mild side effects such as heartburn, nausea, and headaches.

More importantly, doses higher than 5000 mg per day can be toxic and may cause nerve damage.


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