The difference between DL-Phenylalanine, L-Phenylalanine, and D-Phenylalanine

Quick note: Since The Mood Cure helped me so much with my thyroid problems last year, I bought The Diet Cure, and have been reading through it. In short, the power of amino acids blows me away. While I've never felt any different after taking any other "supplements", the difference I've felt by taking amino acids has been amazing.

Today I just want to make a note about the differences between DL-Phenylalanine, L-Phenylalanine, and D-Phenylalanine. Here's a description of Phenylalanine, courtesy of this website:

Phenylalanine is an essential amino acid. Inside the body, it is converted into tyrosine, another amino acid. Tyrosine is then used to produce dopamine and norepinephrine, both neurotransmitters. All of these elements are important because of their relationship to the central nervous system.

From that same website, here are the differences between DL-Phenylalanine, L-Phenylalanine, and D-Phenylalanine:

  • L-phenylalanine is the natural form found in proteins throughout the body.
  • D-phenylalanine is a mirror image of L-phenylalanine, and is synthesized in a laboratory.
  • DL-phenylalanine is a combination of the previous two forms.

The Diet Cure

In her book, The Diet Cure, Julia Ross says that DL-Phenylalanine or D-Phenylalanine is good when you crave the following substances:

  • sweets
  • starches
  • chocolate
  • alcohol
  • flour or milk products
  • fats
  • drugs like Oxycontin, marijuan, or heroin

She also lists the "deficiency symptoms" as:

  • Very sensitive to emotional pain
  • Tear up or cry easily
  • Crave treats for comfort, reward, or numbing
  • Get a "high" from the foods listed previously

This information is listed on page 123 of The Diet Cure.

For more information, here's a link to the Phenylalanine on Wikipedia. These other links were also helpful:


If you're interested in the differences between DL-Phenylalanine, L-Phenylalanine, and D-Phenylalanine, I hope this has been helpful.