Your body cannot create the amino acid phenylalanine on its own from other nutrients, and you must therefore consume it in your diet through food or dietary supplements. It is an amino acid that your body uses to create pain-relieving brain chemicals like L-dopa, a precursor to your brain's reward chemical dopamine. There is no existing research into the use of DL-phenylalanine for pain relief as of 2011.
Initial Research
Phenylalanine is available in three forms. L-phenylalanine is the natural form found in food; D-phenylalanine is a synthetic form and mirror image of L-phenylalanine; and DL-phenylalanine contains both forms of the amino acid together. One of the first studies to examine phenylalanine for pain relief appeared in the journal "Advances in Pain Research and Therapy" in 1983. The study focused on the use of D-phenylalanine, however, and did not examine DL-phenylalanine for this purpose.
Therapeutic Pathway
The 1983 study demonstrated that D-phenylalanine was able to suppress the enzyme enkephalinase in the human body. This enzyme is responsible for the breakdown of enkephalins, which are pain-relieving peptides similar to endorphins. A second small trial the same year was published in the same journal claiming that humans and mice both experienced pain relief while taking D-phenylalanine. However, both studies had design flaws that made their results questionable.
Contradictory Research
Double-blind, placebo-controlled studies that followed the initial findings supporting D-phenylalanine for pain relief showed that the synthetic amino acid is no more effective at chronic pain treatment than placebo. One such study appeared in the July 1986 issue of "Archives of Physical Medicine and Rehabilitation," and examined D-phenylalanine supplementation for four weeks in 30 subjects with chronic pain. Twenty-five percent of the subjects reported more pain relief from D-phenylalanine than placebo, while a nearly equal 22 percent of patients reported that placebo was more effective.
Combined Benefit
Though there are no clinical trials examining the effects of DL-phenylalanine on pain, a 2000 article from A. L. Russell and M. F. McCarty appeared in "Medical Hypotheses" anecdotally supporting the DL-form for this use. The authors claim that their practical experience had shown DL-phenylalanine to be an effective supporter of the body's natural analgesia system. They also stated that DL-phenylalanine can enhance the effects of acupuncture and other methods of stimulating pain relief in your body.
However, the premise of the authors' position revolves around D-phenylalanine's ability to suppress enkephalinase, which clinical trials have disproved. Until researchers complete more significant study of DL-phenylalanine, you should not use it to treat pain without direct advisement from your doctor.
References
- New York University Langone Medical Center: Phenylalanine
- University of Maryland Medical Center; Phenylalanine; Steven D. Ehrlich, N.M.D.; June 2009
- "Archives of Physical Medicine and Rehabilitation"; Analgesic Effectiveness of D-Phenylalanine in Chronic Pain Patients; N. E. Walsh, et al; July 1986
- "Medical Hypotheses"; DL-Phenylalanine Markedly Potentiates Opiate Analgesia -- An Example of Nutrient/Pharmaceutical Up-Regulation of the Endogenous Analgesia System; A. L. Russell and M. F. McCarty; October 2000
