Benign Prostatic Hyperplasia (BPH) is one of the most prevalent urologic disorders in men, affecting 90% of men over 65, which manifests itself as obstructive and irritative symptoms.
Use of stinging nettle root for prostate and irritable bladder complaints has been approved by Comission E. Products made of stinging nettle root have been used to treat the voiding symptoms in stage I and II of BPH and alleviate its symptoms without causing a reduction in the size of the prostate. Based on the views of this commission, stinging nettle root reduces residual urine and increases urine flow.
In numerous pharmacological studies, the following mechanisms of action have been proposed for stinging nettle root extract:
1- The active ingredients in the extract of stinging nettle root, like lignans, bind to Sex Hormone Binding Globulin (SHBG) and prevent it from binding to the prostate.
2- Steroidal compounds present in raw extract of stinging nettle root accelerate the movement of macrophages to their target and aids the anti-inflammatory effects of the drug. Furthermore, steroids inhibit the function of Na+K+ATPase enzyme and therefore inhibit the metabolism and growth of prostate cells.
3- The extract of stinging nettle root inhibits 5α-reductase and aromatase.
4- The extract of stinging nettle root inhibits cellular proliferation in BPH.
In a placebo-controlled clinical trial including 79 patients suffering BHP, stinging nettle root extract (600 mg per day, 5:1 extract for 6-8 weeks) was superior to the placebo in all measured parameters (urine flow and volume, residual urine). In another similar clinical trial, 50 patients with stage I and II BPH, who were administered stinging nettle root extract (600 mg per day, 5:1 extract for 9 weeks), showed considerable reduction in SHBG (p<0.0005) and considerable improvement in urine volume and maximum urinary flow rate.
In a multicenter, double-blind clinical trial, 543 patients with early stages of BPH were administered a combination of extract of saw palmetto fruit (Serenoa repens) and stinging nettle root or finasteride (5α-reductase inhibitor). After 24 weeks, the mean maximum urinary flow rate (Qmax) increased 1.9 ml/s in the group administered extract of saw palmetto fruit and stinging nettle root and 2.4 ml/s in the finasteride group and no statistically significant difference was observed between the two groups (p=0.52). The researchers came to the conclusion that the efficacy of the combination of extract of saw palmetto fruit and stinging nettle root equals that of finasteride and is not associated with the size of the prostate. Nonetheless, better tolerance was observed with the combination of extract of saw palmetto fruit and stinging nettle root compared to finasteride.