Beta-Sitosterol for Prostate: Dosage and Side Effects

Structurally similar to cholesterol, which is the basis of its separate cholesterol-lowering effect through competitive inhibition of intestinal cholesterol absorption. In the prostate the mechanism is less clear: anti-inflammatory activity and effects on 5-alpha-reductase and on prostaglandin metabolism have all been proposed without one being established.

• Urinary symptoms in BPH: weighted mean improvement of 4.9 IPSS points across two studies in the Cochrane analysis, with peak urine flow improved by 3.91 ml/sec and residual volume reduced by 28.62 ml.
• Prostate size: not reduced. The symptoms improve without the gland changing.
• LDL cholesterol: plant sterols generally reduce LDL by competing with cholesterol for absorption, at intakes around 2 g/day.
• Durability: an 18-month follow-up of treated men reported that improvements were maintained.

Wilt 2000 Cochrane systematic review of beta-sitosterols for benign prostatic hyperplasia, covering 519 men across four randomised placebo-controlled double-blind trials of 4-26 weeks, Berges 1995 randomised placebo-controlled trial, and an 18-month follow-up of treated patients. The conclusion that symptoms and flow improve while prostate size does not has held up.

60-130 mg/day of beta-sitosterol in the BPH trials, taken in divided doses, over 4 to 26 weeks. One trial used 180 mg/day of a phytosterol preparation. For cholesterol the relevant intake is much higher, around 2 g/day of total plant sterols, which is usually reached through fortified foods rather than capsules.

Well tolerated in trials, with adverse event rates similar to placebo. Mild GI effects: nausea, indigestion, gas. Erectile dysfunction was reported occasionally in trials, at low rates.

Reduces absorption of fat-soluble vitamins and of beta-carotene at higher intakes. Additive with ezetimibe and statins for cholesterol lowering. People with sitosterolaemia, a rare inherited disorder of sterol handling, must avoid it. Because BPH symptoms can mask prostate cancer, self-treating without a diagnosis is a bad idea.