Known as (DL-Phenylalanine)

Phenylalanine is an essential amino acid found in common protein foods as well as the synthetic sweetener aspartame (NutraSweet). Like other nutrient amino acids, phenylalanine comes in L- (from the Latin levo for left) and D- (from dextro for right) forms. The directions refer to minor differences in the amino acids' molecular structure, as evidenced by light refraction. L-phenylalanine is predominantly a nervous system stimulant, mood enhancer, and appetite suppressant. While D-phenylalanine also apparently has antidepressant properties, it is taken primarily to control chronic pain. Synthetic DL-phenylalanine (DLPA) is half L-phenylalanine and half D-phenylalanine. DLPA has some of the effects of both forms of phenylalanine, although most people take it for the pain-relieving effects of D-phenylalanine.

DLPA supplements have not attracted much scientific attention in recent years. Two studies done in the late 1970s demonstrated potential antidepressant effects for DLPA but have not garnered noticeable follow-up. Studies on D-phenylalanine and DLPA done in the mid-1980s suggesting long-lasting and nontoxic pain-relieving effects have also not generated much subsequent research, although a 1991 study confirmed that DLPA could be used in combination with morphine to reduce the dosage of the opiate and lower its undesirable side effects, including dependence and growth retardation. A 1985 study found that DLPA improved the mood and mood stability of subjects with attention deficit disorder. The researchers noted that a subsequent trial of L-phenylalanine produced no clinical effect.

 

With the help of essential cofactors (such as pyridoxine, a form of vitamin B6), the body transforms phenylalanine in a series of steps into the amino acid tyrosine and then into the important neurotransmitters dopamine and noradrenaline. These neurotransmitters affect brain and nervous system function to elevate mood and increase alertness. D-phenylalanine has also been shown to promote the action in the brain of the small protein molecules known as endorphins and enkephalins. These are natural, morphine-like biochemicals that reduce pain and promote mild euphoria. D-phenylalanine is thought to work by inhibiting the enzymes that normally break down endorphins and enkephalins. This allows endorphins and enkephalins to stay active longer, thus enhancing mood and preventing the perception of pain. D-phenylalanine can also be converted in the body into the compound phenylethylamine, which is thought to have mood-boosting effects.

Forms of phenylalanine can cause symptoms of over-stimulation in some people, such as insomnia and nervousness, although DLPA is generally less stimulating than L-phenylalanine. On occasion people report headaches or nausea from taking DLPA. Certain people should avoid all forms of phenylalanine supplements, such as anyone with high blood pressure and women who are pregnant or lactating. Phenylalanine should not be used by anyone taking MAO inhibitor antidepressants-combining phenylalanine and MAO inhibitors can lead to dangerously high blood pressure. Children, anyone with psychosis, and those suffering from malignant melanoma or the condition known as phenylketonuria, a genetic disorder of phenylalanine metabolism, should also not take phenylalanine supplements.

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References

Beckmann, H., et al., "Dl-phenylalanine in depressed patients: an open study," J Neural Transm (1977), 41 (2-3):123-34

Beckmann, H., et al., "DL-phenylalanine versus imipramine: A double-blind controlled study," Archiv fur Psychiatrie und Nervenkrankheiten (1979), 227 (1):49-58

Dove, B., et al., "[Analgesic effect, tolerance development and dependence potential of D-phenylalanine]," Pharmazie (1985), 40(9):648-50

Dove, B., et al., "[The analgesic action of d-phenylalanine in combination with morphine or methadone]," Pharmazie (1991), 46 (12):875-77

Ehrenpreis, S., "D-phenylalanine and other enkephalinase inhibitors as pharmacological agents: implications for some important therapeutic application," Acupunct Electrother Res (1982), 7(2-3):157-72

Kitade, T., et al., "Studies on the enhanced effect of acupuncture analgesia and acupuncture anesthesia by D-phenylalanine (first report)-effect on pain threshold and inhibition by naloxone," Acupunct Electrother Res (1988), 13(2-3):87-97

Wood, D.R., et al., "Treatment of attention deficit disorder with DL-phenylalanine," Psychiatry Res (1985), 16(1):21-26