Tribulus terrestris

Tribulus terrestris (puncture vine) is a traditional herb marketed for testosterone and libido support. The testosterone claim is not supported by clinical evidence: Santos et al. 2019 (systematic review, 12 RCTs) and Pokrywka et al. 2014 both found no significant effect on serum testosterone in healthy men. Neychev & Mitev 2005 (21 young men, 20 mg/kg/day, 4 weeks) and Rogerson et al. 2007 (22 rugby players, 450 mg/day, 5 weeks) found no effect on testosterone, body composition, or strength. Signals for sexual function exist but are weaker than marketing suggests — Akhtari 2014 and Vale 2018 (small trials in women with HSDD at 750 mg/day) reported modest improvements in sexual desire. Kamenov 2017 (180 men with ED, 1500 mg/day Tribestan) reported improved IIEF scores, but the trial was industry-funded by the product manufacturer (Sopharma). Active constituent is the saponin protodioscin, but product-to-product standardization is inconsistent. No established RDA/UL.