Background

Saw palmetto is the common name for Serenoa repens, a dwarf palm tree native to Florida and other parts of the southeastern United States. The urological effects of the saw palmetto berry were recognized by native Americans who used it as a source of food. Saw palmetto preparations today consist of refined extracts of the dried ripe berry.

Uses

Saw palmetto extract is used to treat symptoms associated with benign prostatic hypertrophy (BPH), a condition found in approximately 40% of men in their fifties and 90% of men in their eighties. It is often used as first-line treatment for BPH in Europe, and in Germany, herbal medications account more than 90% of all drugs prescribed for the treatment of BPH.

In a meta-analysis of 18 randomized controlled trials that compared saw palmetto extract to placebo or standard medical therapies, saw palmetto extract improved urinary symptoms and flow measures significantly compared to placebo. These improvements were comparable to those achieved with finasteride. Saw palmetto extract is less expensive and associated with a significantly lower incidence of impotence compared to finasteride. Others have reached similar conclusions but caution that most trials were significantly limited by methodological flaws, small patient numbers, and brief treatment intervals.

It is not known whether saw palmetto extract can prevent long-term complications of BPH such as acute urinary retention or the need for surgery. Saw palmetto extract does not affect levels of serum prostate specific antigen.

Saw palmetto has been used to treat various other urological conditions and respiratory conditions such as chronic bronchitis, laryngitis, and nasal inflammation.

Phytochemistry and pharmacology

The major constituents of saw palmetto are fatty acids and their glycerides (triacylglycerides and monoacylglycerides), carbohydrates, steroids, flavonoids, resin, pigment, tannin, and volatile oil. The pharmacological activity of saw palmetto has not been attributed to a single compound.

The mechanism of action of saw palmetto is not known, but multiple mechanisms have been proposed. Data from in vitro data studies support the widely held belief that saw palmetto extract, like finasteride, inhibits 5-α reductase. However, results of in vivo studies of inhibition of 5-α reductase by saw palmetto have been inconsistent. Other hypotheses are that saw palmetto exerts its effects by inhibition of dihydrotestosterone binding to the androgen receptors in the prostate, inhibition of estrogen receptors, blocking prolactin receptor signal transduction, interference with fibroblast proliferation, induction of apoptosis, inhibition of α1 adrenergic receptors, and attenuating the inflammatory response.

The pharmacokinetics of the constituents of saw palmetto have not been studied.

Safety

Adverse effects attributed to saw palmetto are mild and usually gastrointestinal in nature. The long-term safety of saw palmetto extract has not been studied. However, it has a long history of safe use in Europe. Saw palmetto should be discontinued before undergo surgery because it may be associated with excessive intraoperative bleeding.

Use during pregnancy or by nursing mothers is not recommended.

Preparations and dosage

Liposterolic extracts are used in virtually all investigational studies. Commercial preparations may be standardized to fatty acid and sterol content. The recommended daily dosage is 1-2 g saw palmetto berry or 320 mg of lipid soluble extract.