Saw Palmetto

History
Early in the century, it was used as a mild diuretic and as a treatment for prostatic enlargement. However, the therapeutic value of the tea came under question and saw palmetto was eventually dropped from the National Formulary. During the 1960s, investigators found relatively high amounts of sitosterols in the dried berries. Various extracts, as well as beta-sitosterol isolated from the berries, exhibited estrogenic activity following parenteral administration in mice. The activity of the extract was low, being only about 1/10,000 as potent as estradiol, and even pure beta-sitosterol was less than 1/10 as strong. Because sitosterols are poorly absorbed following oral administration, there was little to suggest that extracts of the plant had any effect when given orally. Berries contain about 1.5% of an oil, and a purified fat-soluble extract is now available commercially in Europe.

Pharmacology
Although assessments based on earlier research indicated that the plant was of no therapeutic value, a number of more recent studies suggest that extracts of the plant may be beneficial in the management of prostatic enlargement (benign prostatic hypertrophy). A hexane extract of the berries has been shown to have antiandrogenic properties through a direct action on the estrogen receptors and by inhibiting the enzyme testosterone-5-alpha-reductase. Furthermore, saw palmetto extract has been shown to prevent the conversion of testosterone to dihydrotestosterone (DHT) as well as to inhibit DHT binding to cellular and nuclear receptor sites, thereby increasing the metabolism and excretion of DHT. A double-blind placebo-controlled study evaluated the hormonal effects of saw palmetto extract given to men with benign prostatic hypertrophy (BPH) for 3 months prior to operation. The study found that saw palmetto displayed an estrogenic and antiprogesterone effect as determined by estrogen and progesterone receptor activity. The results from numerous double-blinded trials and open trials of the effects of saw palmetto extract in benign prostatic hypertrophy have been reported. Typically, these studies have been small and of approximately 3 months duration. In one of the larger trials, 110 patients each received either a hexane extract of saw palmetto or placebo under double-blind conditions for 30 days. Active treatment consisted of 320 mg/day of a commercially available 80 mg tablet preparation. Treatment was assessed based on objective measure such as nocturia, intensity of dysuria, flow rate, post-micturition residue, and subjective patient and physician assessments. S repens extracts were statistically superior to placebo for every parameter after 30 days of treatment. In a study of 45 patients with BPH, prazosin (i.e., Minipress) was found to be only marginally more effective than saw palmetto extract when given for 12 weeks, as measured by flowmetry and subjective assessments of irritation.
The hexane extract of saw palmetto has also been shown to possess antiallergic and anti-inflammatory activity in rats, mice, and guinea pigs. The German Commission E recommends a daily dose of 1-2 g (about 1-2 dried berries) or 320 mg of a lipid-soluble extract of saw palmetto for treatment of BPH.