D-aspartic acid: does it raise testosterone?

D-aspartic acid (DAA) became a popular "testosterone booster" after a 2009 study reported higher testosterone in men taking it for 12 days. Later trials in men who actually lift weights told a different story: no effect at 3 g a day, and a drop in testosterone at 6 g a day in one study. It has no role in aerobic fitness.

What it is

D-aspartic acid is the mirror-image form of the amino acid L-aspartic acid. It occurs naturally in the pituitary gland and testes, where animal studies show it can stimulate release of luteinising hormone (LH) and testosterone. Supplements are usually sold as sodium D-aspartate powder or capsules.

Does it raise VO2max?

No. Nothing in the DAA research suggests an effect on the heart, blood volume or haemoglobin, which set VO2max (see what limits VO2max). Testosterone does influence haemoglobin, but DAA has not reliably raised testosterone at all in trained men (see testosterone, endurance training and VO2max).

Does it improve endurance performance?

There is no evidence that it does. All the human trials focus on hormones, strength and muscle.

Topo et al., 2009 — the study that started it

In this paper (Reprod Biol Endocrinol, 2009), 23 men took a daily D-aspartate product for 12 days and 20 men took a placebo. The authors reported higher LH and testosterone in the DAA group, along with rat experiments showing the mechanism. The men were not resistance trained, and the study has not been replicated in trained athletes.

Willoughby and Leutholtz, 2013 — 3 g a day, 28 days

Resistance-trained men took 3 g of DAA or placebo daily while training four times a week for 28 days (Nutr Res, 2013). Both groups gained strength and lean mass from training, but total and free testosterone, LH and estradiol were unchanged, and DAA added nothing. The authors concluded it had no anabolic or ergogenic effect.

Melville et al., 2015 — 3 g versus 6 g

In 24 men with at least two years of lifting experience, 3 g a day for 14 days had no effect on testosterone, while 6 g a day significantly reduced total and free testosterone (J Int Soc Sports Nutr, 2015). Starting testosterone did not predict who responded.

Melville et al., 2017 — 6 g a day, 12 weeks

A follow-up randomised trial gave 22 trained men 6 g of DAA or placebo during 12 weeks of supervised training (PLoS One, 2017). Testosterone did not change, estradiol fell, and both groups gained the same strength and muscle size. The authors concluded DAA is ineffective at changing testosterone or improving training outcomes.

Roshanzamir and Safavi, 2017 — systematic review

This review found that DAA raised testosterone in many animal studies, but the four human studies gave inconsistent results, and the evidence was "sparse" because of the small number and poor quality of trials.

How it is used in studies

Human trials used 3 g or 6 g a day for 12 days to 12 weeks. No dose has been shown to raise testosterone in trained men, and 6 g a day lowered it in one short trial.

Side effects, safety and anti-doping

Short trials did not report serious side effects, but long-term safety in humans has not been studied. DAA is often one ingredient in multi-ingredient booster blends, which is where most risk lies.

DAA itself is not prohibited by WADA, but "testosterone booster" products are among the most contaminated supplements. An international study (Geyer et al., 2004) found 14.8% of 634 supplements contained anabolic steroids not declared on the label, and FDA warnings link most adulterated muscle-building products to synthetic steroids (Tucker et al., 2018). Under WADA's strict liability rule, athletes are responsible for anything in their sample. If you compete, use only products certified by Informed Sport or NSF Certified for Sport.

This page is not medical advice. Men with symptoms of low testosterone, such as low libido, erectile problems, fatigue, low mood or loss of muscle, should see a doctor for testing rather than self-treat.

Who might benefit

There is no group in which the evidence clearly supports DAA for testosterone or performance. Interest in it for male fertility exists, but that is a medical question for a doctor. For strength and muscle, use the basics: creatine, enough protein and consistent strength training.

Bottom line

D-aspartic acid's reputation rests on a 12-day study in untrained men. In trained men, three controlled trials found no benefit, and one found lower testosterone at 6 g a day. It does not raise VO2max. Compare other testosterone boosters such as fenugreek and zinc, or see how to improve VO2max.

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.
• 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 in resistance-trained men. Nutr Res. 2013;33(10):803–810.
• 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;12:15.
• 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;12(8):e0182630.
• 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.
• Geyer H, Parr MK, Mareck U, Reinhart U, Schrader Y, Schänzer W. Analysis of non-hormonal nutritional supplements for anabolic-androgenic steroids: results of an international study. Int J Sports Med. 2004;25(2):124–129.
• Tucker J, Fischer T, Upjohn L, Mazzera D, Kumar M. Unapproved pharmaceutical ingredients included in dietary supplements associated with US Food and Drug Administration warnings. JAMA Netw Open. 2018;1(6):e183337.