Evidence summary
What it is: An amino acid involved in the release of luteinising hormone.
Studied dose: 2,000 to 3,000mg daily in the trials that found an effect.
Evidence quality: Mixed, and this matters. Positive initial findings, failed replications.
Our reading: Possibly useful in untrained men with low baseline. Not established in trained men.
The initial finding
A 2009 study reported that 3,120mg of sodium D-aspartate daily for 12 days increased luteinising hormone and testosterone in men, with testosterone rising by around 42% in the treatment group.1 The proposed mechanism was action at the hypothalamus and pituitary, increasing the release of LH, which in turn signals the testes.
That is a large effect, mechanistically plausible, and it drove DAA into a great many formulations.
What happened next
Replication has not been kind.
A 2013 study in resistance-trained men found that 3,000mg daily for 28 days produced no significant change in total or free testosterone.2 A 2015 study went further: at 6,000mg daily, it reported a decrease in testosterone, alongside no benefit at 3,000mg.3
The most coherent reading of the whole body of work is that DAA may raise testosterone in men who are untrained, older, or starting from a low baseline, and does little or nothing in trained men with normal levels. That is a much narrower claim than the one the ingredient is usually sold on.
Why we weight this heavily
DAA is the reason our scoring rubric rewards replication rather than headline effect size. An impressive single study that later trials fail to reproduce is common in nutritional science, and treating it as settled is how a category ends up full of ingredients that do not work.
Dose
The trials that found an effect used 2,000 to 3,000mg daily. This is a bulky dose: it is difficult to deliver in a two-capsule serving alongside other actives, which is why formulas including DAA at a trial-level dose tend to have a high pill burden.
Formulas that include DAA at a few hundred milligrams are including it at a fraction of any studied dose. That is worth knowing, though given the replication problem it is a less serious omission than it would be for a better-supported ingredient.
Safety
Generally well tolerated at 3,000mg daily in the trials conducted. The 2015 finding of reduced testosterone at 6,000mg is a reason not to exceed the studied range on the assumption that more is better.
Bottom line
DAA is not a scam, but it is not the ingredient its marketing suggests. If you are untrained or starting from a genuinely low baseline, the initial evidence may apply to you. If you are training regularly with normal levels, the replication attempts suggest you should not expect much. Either way, a formula built primarily around DAA is resting on the weakest foundation in this category.
References
- Topo E, Soricelli A, D'Aniello A, Ronsini S, D'Aniello G. The role and molecular mechanism of D-aspartic acid in the release and synthesis of LH and testosterone in humans and rats. Reproductive Biology and Endocrinology. 2009;7:120.
- Willoughby DS, Leutholtz B. D-aspartic acid supplementation combined with 28 days of heavy resistance training has no effect on body composition, muscle strength, and serum hormones associated with the hypothalamo-pituitary-gonadal axis. Nutrition Research. 2013;33(10):803-810.
- Melville GW, Siegler JC, Marshall PW. Three and six grams supplementation of D-aspartic acid in resistance trained men. Journal of the International Society of Sports Nutrition. 2015;12:15.