D-aspartic acid (DAA)

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 (Nutr Res) in 24 trained men showed no changes in total or free testosterone with DAA 6 g/day × 14 days vs placebo; Willoughby 2013 in 20 trained men at 3 g/day × 28 days also showed no changes. 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.

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.