D-Aspartic Acid and Testosterone: Why the Early Study Didn't Hold Up
D-aspartic acid, often written as DAA, is one of the most common ingredients in testosterone boosters. It is usually listed near the top of the label, in large doses. I'm not a doctor, and this is not medical advice. Here is what the research says, in the order it was published. For the big picture, see my guide on whether testosterone boosters work.
What is D-aspartic acid?
It is an amino acid that occurs naturally in the body, mainly in the pituitary gland and the testes. In animal studies it appears to play a role in releasing hormones that drive testosterone production. Supplement makers took that idea and put it in a capsule.
What did the first human study find?
The study that launched the ingredient was published in 2009. Researchers gave 23 men 3.12 g of D-aspartic acid a day for 12 days. Compared with the starting point, luteinizing hormone (LH) rose about 33% and testosterone about 42% (Topo et al., 2009). That is a big number, and it is the one many sellers still quote.
Two things to keep in mind. It was short, 12 days. And one study is a starting point for more research, not a conclusion.
What happened when other researchers tested it?
| Study | Who and how | Result |
|---|---|---|
| Melville et al., 2015 | Resistance-trained men, 3 g or 6 g a day | 3 g: no significant effect on testosterone. 6 g: total and free testosterone decreased. |
| Melville et al., 2017 | 19 resistance-trained men (average age about 24), 6 g a day for 12 weeks, with supervised training, double-blind with placebo | No change in basal total or free testosterone. Estradiol fell about 16% in the D-aspartic acid group. Strength and muscle gains were similar to placebo. |
The 2017 trial is the more useful one: it was longer, it used a placebo group, and it measured strength and muscle too. Its conclusion was that D-aspartic acid did not change testosterone or improve training results.
What do the systematic reviews say?
A 2017 systematic review pulled together 23 animal studies and 4 human studies. In animals, giving D-aspartic acid raised testosterone. In humans, the results were inconsistent, and the authors noted the evidence is sparse because there are few studies and some are of poor quality. They called for larger and longer human trials (Roshanzamir and Safavi, 2017).
Why do the results differ?
Nobody knows for sure. Possible explanations include differences in who took part (the 2009 study and the later ones used different groups of men), how long they took it, and how big the studies were. The later trials were also small, with 19 men in the 2017 one. That is a reason to be cautious in both directions. It is not proof that the ingredient can never work in anyone.
Is D-aspartic acid worth taking?
Based on the trials I found, I wouldn't pay for it. The best-designed trial in trained men found no testosterone change, and one earlier trial at 6 g found a drop. If you are already buying a product that contains it, check these points:
- Is the dose printed on the label, or hidden inside a "proprietary blend"?
- Does the dose match what was studied (about 3 g a day)?
- Is D-aspartic acid doing most of the work, with nothing else that has good evidence?
We also know little about long-term safety. If you take medication or have a health condition, ask your doctor first. For the full buying checklist, see the pillar guide. If you want ingredients with better evidence, read about tongkat ali and ashwagandha.
Frequently asked questions
Does D-aspartic acid raise testosterone?
A small 2009 study reported a rise after 12 days at about 3 g a day. Later trials in resistance-trained men found no increase, and one found a decrease at 6 g a day. A 2017 review called the human evidence inconsistent.
What dose of D-aspartic acid did the studies use?
About 3 g a day in the 2009 study and in one arm of the 2015 trial, and 6 g a day in the other trials.
Does D-aspartic acid help build muscle?
In the 2017 trial, strength and muscle gains in men taking D-aspartic acid were similar to those on placebo.
Is D-aspartic acid safe?
Long-term safety is not well studied, and supplement quality varies. Talk to your doctor or pharmacist before you take it, especially if you use medication.
Sources
- 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. Reprod Biol Endocrinol. 2009;7:120. doi:10.1186/1477-7827-7-120
- Melville GW, Siegler JC, Marshall PWM. Three and six grams supplementation of d-aspartic acid in resistance trained men. J Int Soc Sports Nutr. 2015. doi:10.1186/s12970-015-0078-7
- Melville GW, Siegler JC, Marshall PWM. The effects of d-aspartic acid supplementation in resistance-trained men over a three month training period: a randomised controlled trial. PLoS ONE. 2017. doi:10.1371/journal.pone.0182630
- Roshanzamir F, Safavi SM. The putative effects of D-aspartic acid on blood testosterone levels: a systematic review. Int J Reprod Biomed. 2017;15(1):1-10. Journal page
Marcus Hale
Writer at The Male Ledger. Not a doctor.
I write about testosterone, energy and vitality after 40, and I link to the studies so you can check my work. Marcus Hale is a pen name; here is why.