Most testosterone boosting supplements include D-aspartic acid, often listed as DAA or D-asp, as the first ingredient. There is some debate as to whether or not D-aspartic acid is effective. D-aspartic acid is not intended to be used by people under 21 years of age. Always consult with your physician before using any supplements.
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Amino Acid Nomenclature
All amino acids, except glycine, that are used by the human body for protein synthesis have two nearly identical forms, noted as L- or D-. These designations refer to how parts of the molecule react under an optical light. With regards to protein synthesis and muscle growth, only the L- forms are used for this process. The D- form of the amino acids are also found within the human body and can be used in a variety of processes as well.
What is Aspartic Acid?
Aspartic acid is an amino acid which contains an acidic side chain and is considered to be non-essential. This means that the human body can make sufficient amounts of it if adequate amounts of essential amino acids are consumed. L-aspartic acid is known to participate in the development of the molecules that help make DNA.
Aspartic Acid and Testosterone
With regards to testosterone, D-aspartic acid is utilized, not the L- form. A study at the University of Naples using birds demonstrated that D-aspartic acid reacts within the brain to release luteinizing hormone, or LH. LH then travels to the testicles where it enters the specialized cells, or Leydig cells, which have the function of creating testosterone. Articles published by "Brain Research Reviews" concur with the proposed action of D-aspartic acid and its effects on testosterone.
D-Aspartic Acid and Humans
Animal studies showing the effectiveness are great, but studies using those same supplements on humans are inconclusive. There are few studies performed using D-aspartic acid and humans. One study in "Reproductive Biology and Endocrinology" showed that males supplemented with 3.12 g of D-aspartic acid for 12 days experienced an increase in their free testosterone by approximately 40 percent. After three days of no use, their free testosterone levels dropped by about 10 percent.
Long-term studies have not been performed using D-aspartic acid. Most manufacturers of products containing D-aspartic acid recommend using the product for periods of 4 to 12 weeks followed by a period of cessation from the product lasing 2 to 4 weeks. Always read the label on the supplement you are taking and use that recommendation accordingly. Current recommendations based on "Reproductive Biology and Endocrinology" suggest using 3.12 g per day.