Benign prostate enlargement (benign prostatic hyperplasia) refers to the increase in size of the prostate and is characterized by hyperplasia of prostatic stromal and epithelial cells. This can result in the formation of nodules which can obstruct the urethra and can interfere with the normal flow of urine. Patients with prostate enlargement can experience symptoms such as urinary retention, frequent urination, urinary hesitancy and increased risk of urinary tract infections.
Two German clinical studies have confirmed the beneficial effects of beta-sitosterol in patients with prostate enlargement. The first study conducted by Klippel and coworkers showed that using 130 mg per day of beta-sitosterol significantly improved the condition of the patients: the international prostate symptom score increased by 5.4 points, post-void residual urinary volume decreased and peak urinary flow rate increased . Another double-blind trial involving 200 men with benign prostate enlargement showed that the intake of 20 mg of beta-sitosterol three times a day for six months significant improved urinary flow and other symptoms. Administration of the sterol had no effect on the volume of the prostate. Also this study concluded that significant improvement in symptoms and urinary flow parameters show the effectiveness of beta-sitosterol in the treatment of benign prostate enlargement.
 Klippel KF, Hiltl DM, Schipp B. "A multicentric, placebo-controlled, double-blind clinical trial of beta-sitosterol (phytosterol) for the treatment of benign prostatic hyperplasia." Br J Urol. 1997 Sep;80(3):427-32.
 Berges RR, Windeler J, Trampisch HJ, Senge T. " Randomised, placebo-controlled, double-blind clinical trial of beta-sitosterol in patients with benign prostatic hyperplasia." Lancet. 1995 Jun 17;345(8964):1529-32.