Almost every male (especially in their teens, twenties, and some in their thirties) want to get big. They want large 
bulging muscles which can’t be confined to a reasonable fitting shirt. This results in many seeking supplementation for enhanced muscle development. Many of these supplements promise muscle gain, but do they really work?
I’m a documentary fiend. I watch numerous documentaries and one of my favorites is Bigger, Stronger, Faster. Like all things in life, I feel this documentary is biased towards the pro-steroid use. Nonetheless, it has a lot of great points and most importantly is entertaining.
The anabolic hormone testosterone is a key determinant of training induced muscle gain. When testosterone circulates the blood, it directly interacts with receptors and cells stimulating muscle growth. Currently it is unknown whether boosting testosterone levels within normal physiological levels (mid-range to upper-range) will have a significant effect on strength and hypertrophy. Nonetheless, the supplement industry is endorsing testosterone boosters to improve training related gains. D-aspartic acid is currently recommended as a viable product to significantly raise testosterone, however research in humans only supports this recommendation in untrained men with below average testosterone levels.
Aspartic acid (C4H7NO4) is an α-amino acid which is known to exist in two isoforms, l-aspartic acid and d-aspartic acid. (2R)-2-aminobutanedioic acid or d-aspartic acid (DAA). Free DAA is found in tissues and cells related to the central nervous and endocrine systems. Free DAA is found in tissues and cells related to the central nervous and endocrine systems. DAA is believed to stimulate the production and release of testosterone through multiple pathways of the hypothalamic-pituitary-gonadal (HPG) axis.
With all this talk about DAA, it seems it should clearly increase free testosterone and boost muscle growth…well we still need research to accredit this claim.
Study on d-Aspartic Acid
Luckily, Geoffrey Melville and his colleagues at the University of Western Sydney were also interested. This group of researchers had 24 participants (18-36 years) with weight lifting experience (able to bench press 100% bodyweight). For the study:
“Participants were assigned to one of three experimental groups: placebo (D0), three grams of DAA (D3) and six grams of DAA (D6). All participants consumed 10 opaque capsules each morning with breakfast for two weeks. They contained either: six grams of flour (D0, n = 8); a mixture of three grams each of flour and DAA (D3, n = 8); or six grams of DAA (D6, n = 8).”
The testing included a fasted blood draw, then 1-RM bench press evaluation. Through the duration of the experiment the participants trained 4 days per week for one month. All the participants performed four sets of repetition maximum ranged between 8 – 10. Exercises during the upper body session were: barbell bench press; overhand pulldown; barbell overhead press and underhand pulldown. The lower body session consisted of: back squat; good morning; leg extensions; and straight leg calf raises.
Overall, there were no significant changes in testosterone between groups.
The author’s concluded the following findings:
“[t]he primary findings of the current study were, 1) resistance trained men consuming six grams of d-aspartic acid daily demonstrated significant reductions in total and free testosterone after 14 days of d-aspartic acid supplementation, and 2) the responsiveness to d-aspartic acid supplementation was unaffected by initial testosterone levels (total or free) in resistance trained men.”
Now, this shouldn’t completely discredit the use of d-aspartic acid, but it should highly discourage it until further research can substantiate the claims of its use in men with normal testosterone levels. Until this occurs, it seems d-aspartic acid is another highly touted supplement, with little backing. Don’t waste your money on this compound, just sleep more, eat well, and reap the benefits of the cost effective!
Reference:
- Melville GW, Siegler JC, Marshall PW. Three and six grams supplementation of d-aspartic acid in resistance trained men. J Int Soc Sports Nutr. 2015 Apr 1;12:15. doi: 10.1186/s12970-015-0078-7. eCollection 2015.