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DL-Phenylalanine for ADHD

By Ryan Haas ; Updated August 14, 2017

Phenylalanine is an essential amino acid present primarily in animal-based foods such as beef, poultry, fish and eggs. The natural form of this amino acid is L-phenylalanine, and the synthetic form is D-phenylalanine. DL-phenylalanine conbines both forms, and some proponents of the supplement claim it can aid in the treatment of attention deficit hyperactivity disorder, or ADHD.

Causes of ADHD

There is not a clear cause established for ADHD, according to the University of Arkansas for Medical Sciences. Some studies have revealed that people with ADHD may have smaller than normal sections in their brains, such as the frontal lobes in the cerebral cortex. If you have ADHD, you may also have lower than normal levels of dopamine, which is a neurotransmitter that aids in muscle control. Proponents of DL-phenylalanine for ADHD feel that it can increase your dopamine levels.

DL-Phenylalanine Role

DL-phenylalanine has shown some potential as a treatment for depression. Gene Bruno of the Huntington College of Health Sciences states that some small trials and double-blind studies have shown DL-phenylalanine is effective at treating depression by preventing the breakdown of chemicals in your brain. Phenylalanine is also a part of L-DOPA, a precursor to dopamine.

Clinical Trials

Despite claims that DL-phenylalanine can relieve the symptoms of ADHD, the limited research published in this area does not indicate the amino acid is likely helpful. Double-blind studies appeared in the “Psychiatry Research” journal and the “American Journal of Psychiatry” in 1985 and 1987, respectively. Both studies compared phenylalanine supplementation against placebo for two weeks. The former trial showed benefits “approaching significance” for patients with ADHD, but these effects faded when subjects continued to take DL-phenylalanine for three months. The latter trial showed no behavioral benefits with the supplement.


Speak to your doctor before taking DL-phenylalanine as a potential treatment for ADHD, as there is not a clear dosage established for this purpose. The New York University Langone Medical Center states that recommended doses of DL-phenylalanine are typically between 100 mg and 200 mg per day for depression. Maximum safe doses for phenylalanine are not well established.

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