Evidence Level
Stinging nettle root is a well-documented treatment for benign prostatic hyperplasia (BPH) in European phytotherapy. It has been approved as such in Germany and Austria, as outlined in the Commission E monograph. A pivotal study by Safarinejad et al. (2005) involved a randomized, double-blind, placebo-controlled crossover trial with 620 men diagnosed with BPH. Participants received either 600mg of nettle root extract or placebo daily for six months. The nettle group demonstrated significant improvements in International Prostate Symptom Score (IPSS), maximum urinary flow rate, and post-void residual volume compared to the placebo group (P < 0.001).
Lopatkin et al. (2005) conducted a double-blind, placebo-controlled trial with 257 men over 48 weeks, evaluating a fixed combination of saw palmetto (160mg) and nettle root (120mg), known as PRO 160/120. The study found this combination to be comparable to finasteride 5mg in improving IPSS scores, while reporting fewer sexual side effects.
The mechanism underlying nettle root's efficacy was elucidated by Schottner et al. (1997). They identified specific lignans, including secoisolariciresinol and its derivatives, which bind to human sex hormone binding globulin (SHBG) in vitro, competing with testosterone for SHBG binding sites. This mechanism contributes to nettle root's ability to alleviate symptoms associated with BPH.