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Item #: 0132
Reg. Price: $16.99
Our Price: $10.99

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L-Phenylalanine 500 mg - 120 Caps

L-Phenylalanine is an essential, nine-carbon amino acid and is a precursor to the amino acid tyrosine. Because tyrosine is necessary for the synthesis of proteins and the production of the neurotransmitters dopamine and norepinephrine, phenylalanine is an extremely important nutrient that must be obtained through the diet or supplementation.

The primary use of L-phenylalanine in the body is in the production of tyrosine, another amino acid. Tyrosine is the precursor of monoamine neurotransmitters such as dopamine, epinephrine and norepinephrine. Given the importance of these brain chemicals, phenylalanine is important to maintain adequate levels of monoamine neurotransmitters in the brain.

L-phenylalanine crosses into the brain, it is converted to L-tyrosine and then to L-dopa. However, to cross the blood-brain barrier, L-phenylalanine shares the same transport mechanism with tryptophan. Tryptophan is another amino acid essential for the synthesis of serotonin, a neurotransmitter important to mood. When phenylalanine is ingested in large amounts, it can reduce the absorption of tryptophan into the brain and, by extension, reduce the production of serotonin. A phenylalanine deficiency can cause mental confusion, reduced alertness, lethargy, depression, memory impairment and loss of appetite.

 At high doses, L-phenylalanine can actually serve as both an analgesic and an antidepressant. It achieves this feat by blocking a subgroup of calcium channels in the brain. Other effects of L-phenylalanine in the brain include the antagonism of glycine and glutamate at specific receptors in the cortex and hippocampus. These antagonism of inhibitory neurotransmitters can also contribute to the antidepressant effect of the amino acid.

Serving Size: 1 Capsule
Servings Per Container: 120

  Amount Per Serving % Daily Value
L-Phenylalanine   500 mg    

Serving Size: 1 Capsule

Suggested Use: As a dietary supplement, take 1 capsule, 1 to 3 times a day as needed, preferably between meals.

Free of: sugar, salt, starch, yeast, wheat, gluten, corn, soy, egg, milk or preservatives.

Other Ingredients: Gelatin (capsule).

Warnings: Persons with high blood pressure should consult a physician before using.


Our body uses Phenylalanine to make chemical messengers that may ward away several unsavory possible afflictions. Some people believe that Phenylalanine supplements such as this one from Now may help with attention issues.

Our body converts phenylalanine to tyrosine‚ which is then converted to the neurotransmitters‚ dopamine‚ dopa‚ norepinephrine and epinephrine. Many scientists believe that L-phenylalanine could combat mood swings caused by premenstrual syndrome and chronic pain. There are people who believe that L-phenylalanine in our diet may increase energy and mental alertness along with our ability to focus better.

When our body goes through pain it releases a protein‚ enkephalinase. Some studies believe that this Now supplement may effectively block the action of this protein and provides good pain relief. There are further studies that state that L-phenylalanine may help with weight loss conditions by reducing the urge to eat.



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