Sitosterol, specifically β-sitosterol, is a plant-derived sterol that has been studied for its effects on symptoms of benign prostatic hyperplasia (BPH), a non-cancerous enlargement of the prostate gland commonly affecting older men. The scientific evidence supporting its use is modest but present. Several randomized, placebo-controlled trials and meta-analyses have evaluated the effects of β-sitosterol on urinary symptoms and flow measures in men with BPH. A notable meta-analysis published in the journal The Lancet (1995) pooled data from four randomized trials (519 men) and found that β-sitosterol improved urinary symptom scores and increased peak urinary flow compared to placebo. However, these studies were relatively short-term (4-26 weeks), and there is a lack of long-term outcome data.

The mechanism by which sitosterol alleviates symptoms is not fully understood, but it is believed to influence prostate and urinary function, possibly by anti-inflammatory activity or modulation of growth factors. Importantly, sitosterol does not appear to reduce prostate size, distinguishing it from some pharmaceutical therapies. Major guideline bodies such as the American Urological Association recognize the modest benefit of phytotherapeutics like sitosterol but do not recommend them as first-line treatments due to limited high-quality data and lack of long-term safety information.

In summary, while there is some scientific validation for the use of sitosterol in BPH symptom relief, the evidence is not robust and does not support it as a replacement for conventional therapies.