D-aspartic acid (DAA)

D-aspartic acid is marketed to improve semen analysis on the strength of D'Aniello 2012, where sperm concentration and motility roughly doubled over 90 days in 60 subfertile men. That study was open-label, had no placebo and no randomization, and appeared in a journal not indexed in PubMed, so it cannot establish the effect. A 2017 systematic review by Roshanzamir and Safavi found only four human trials and rated the evidence sparse and inconsistent, while a placebo-controlled trial in trained men (Melville 2017) showed no rise in testosterone. The one positive randomized placebo-controlled trial (GamalEl Din 2025) combined D-aspartic acid with ubiquinol and zinc, so its benefit cannot be attributed to the amino acid alone. No serious adverse effects are documented at roughly 2.66 g per day, but a fertility benefit remains unproven.

ICD-10: N46.9 · ICD-11: GB04

D-aspartic acid is a popular «natural testosterone booster» in biohacking and sport segments, sold on the Topo 2009 paper about +42% testosterone over 12 days. Modern RCTs refute the result: Melville 2017 (PLoS One) in 22 trained men showed no change in total or free testosterone with DAA 6 g/day over 12 weeks vs placebo. Willoughby 2013 in 20 men at 3 g/day for 28 days also showed no change. Moreover, Melville 2015 found that 6 g/day lowered total testosterone, so the supplement does the opposite of what it promises. Endocrine Society 2018 in confirmed hypogonadism recommends testosterone replacement therapy; DAA is in no international guideline. If DAA was recommended for «low testosterone» without proper workup, consider seeking a second opinion from an endocrinologist.

ICD-10: E29.1 · ICD-11: 5A81.1

DAA is sold in pre-workout formulas and «testosterone boosters» as a muscle gain product on the hormone-mediated hypertrophy hypothesis. No evidence base: Willoughby 2013 and Melville 2017 RCTs in trained men showed no clinically meaningful DAA effect on lean body mass and strength. For muscle gain IOC 2018 and ISSN 2015 list creatine monohydrate (3–5 g/day), adequate protein (1.6–2.2 g/kg), progressive overload and caloric surplus; DAA is not in the IOC-approved sports supplement list.