Studies in Men with Enlarged Prostates:
A meta-analysis of randomized, controlled, phytotherapy-based trials for benign prostatic hyperplasia (BPH) identified 5 studies involving nettle (1). Of these studies, only 2 small studies (41 and 50 patients) used single-ingredient nettle products. The results of these single-ingredient studies were somewhat contradictory; with one reporting notable improvement in urinary symptom scores relative to placebo, and the other reporting improvements in peak urine flow but not in urinary symptom scores relative to placebo (1,2,3). While the authors of the analysis acknowledged the need for additional randomized controlled trials, they concluded that nettle extracts by themselves probably do not improve the symptoms of BPH (1).
There was much more consistency in the findings of the 3 trials that used combination nettle preparations. Two of these trials used saw palmetto/nettle mixtures and had a placebo control group. Both of these trials saw significant improvement in maximum urine flow rate and urinary symptom scores in the treatment group relative to placebo. It should be noted, however, that only one of the trials used a validated urinary symptom-scale score (the International Prostate Symptom Score) while the other used a physician-assessed symptom questionnaire. The remaining study compared a saw palmetto/nettle mixture to the pharmaceutical drug finasteride. This ‘higher-powered’ study, involving 543 men, found that there were no significant differences in urinary symptom score (IPSS), maximum urine flow, or residual urine volume between the supplement and finasteride groups at the conclusion of the 12 week long treatment period (1). This indicates that the mixed nettle product may be as effective at relieving symptoms as finasteride.
At least two additional randomized, double-blind, controlled trials investigating the efficacy of mixed saw palmetto/nettle supplements have been published since the publication of the aforementioned meta-analysis (4,5,6). One trial treated 257 men with placebo or a mixed saw palmetto/nettle supplement for 24 weeks. At the conclusion of this trial period, blinding was removed and all participants were given the mixed supplement for another 24 weeks. 219 of the men who completed this study elected to continue taking the mixed supplement for another 48 weeks as part of a long-term follow-up study. The authors of this study reported that patients treated with the supplement had a significantly larger decrease in urinary symptom score (IPSS) than those treated with placebo during the controlled portion of the study (6 point reduction compared to 4 point reduction) (4,5). During the 72 week follow-up phase, in which all participants were treated with supplement, patients continued to experience improvements in IPSS scores resulting in an overall average score reduction of 9 points. At the conclusion of this follow-up phase, changes in mean values from baseline for maximum urinary flow, average urinary flow, and prostate volume were also significant (18.9%, 18.6%, and 6.7% reduction respectively) (5). The second trial compared the same mixed supplement against tamsulosin. This study included 140 BPH patients and lasted for 60 weeks. Reductions in IPSS scores were comparable, with no statistically significant difference, between both treatment groups. “The median intraindividual decrease of IPSS total score was 9 points in both groups” (6). While these results are compelling, it should be noted that both trials used the same fixed combination of saw palmetto and nettle (160mg fruit extract and 120mg root extract respectively). Other mixed products containing different amounts or ratios of these ingredients may or may not have similar efficacy.
- Wilt TJ, Ishani A, Rutks I, MacDonald R. Phytotherapy for benign prostatic hyperplasia. Pub Health Nutr. 2000;3(4A):459-472. doi:10.1017/S1368980000000549.
- Vontobel HP, Herzog R, Rutishauser G, Kres H. Results of a double-blind study on the effectiveness of ERU (extractum radices Urticae) capsules in conservative treatment of benign prostatic hyperplasia. Urologe. 1985;24(1):49-51.
- Engelmann U, Boos G, Kres H. Therapie der benignen prostatahyperplasie mit bazoton liquidum. Urologe. 1996;36(4):287-291.
- Lopatkin N, Sivkov A, Walther C, Schlafke S, Medvedev A, Avdeichuk J, Golubev G, Melnik K, Elenberger N, Engelmann U. Long-term efficacy and safety of a combination of sabal and urtica extract for lower urinary tract symptoms-a placebo-controlled, double-blind, multicenter trial. World J of Urol. 2005;23(2):139-146. doi:10.1007/s00345-005-0501-9.
- Lopatkin N, Sivkov A, Schlafke S, Funk P, Medvedev A, Engelmann U. Efficacy and safety of a combination of sabal and urtica extract in lower urinary tract symptoms-long-term follow up of a placebo-controlled, double-blind, multicenter trial. Int Urol Nephrol. 2007;39:1137-1146. doi:10.1007/s11255-006-9173-7.
- Engelmann U, Walther C, Bondarenko B, Funk P, Schlafke S. Efficacy and safety of a combination of sabal and urtica extract in lower urinary tract symptoms. Arzneim Forsch Drug Res. 2006;56(3):222-229.