Saw Palmetto

Scientific Name(s): Serenoa repens (Bartram) Small. Also referred to as Sabal serrulata (Michx.) Nicholson or Sabal serrulatum Schult. Family: Palmae (palms)

Common Name(s): Saw palmetto , sabal , American dwarf palm tree , cabbage palm , fan palm , scrub palm

Clinical Overview

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Uses of Saw Palmetto

Saw palmetto is used to treat symptoms of benign prostatic hyperplasia, including reduction of urinary frequency, increase of urinary flow, and decrease of nocturia. Saw palmetto may delay the need for prostate surgery.

Saw Palmetto Dosing

The crude saw palmetto berries usually are administered at 1 to 2 g/day; however, lipophilic extracts standardized to 85% to 95% fatty acids in soft native extract or 25% fatty acids in a dry extract are more common. Some of the brand name products include Permixon ( Pierre Fabre Medicament ), Prostaserene ( Indena ) SCF extract, Prostagutt (WS 1473, Schwabe ), Remigeron ( Schaper & Brummer ), IDS 89 ( Strathmann AG ), Quanterra Prostate ( Warner Lambert ), and LG 166/S ( Lab. Guidotti ). Typical doses of standardized extracts range from 100 to 400 mg given twice daily for benign prostatic hypertrophy.

Contraindications

Contraindications have not yet been identified.

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Saw Palmetto Interactions

Increased anticoagulant effect of warfarin has been reported during concurrent ingestion of saw palmetto. However, there was a more likely explanation for the interaction. Until more data are available, patients taking warfarin should consult their health care provider before taking saw palmetto or other herbal products.

Saw Palmetto Adverse Reactions

Saw palmetto is generally well tolerated, with occasional reports of adverse GI effects; do not use in pregnancy. Because of well-documented antiandrogen and antiestrogenic activity, avoid taking with any hormone therapy including oral contraceptive and hormone replacement therapy.

Toxicology

Research reveals little or no information regarding toxicology with the use of saw palmetto.

Botany

The saw palmetto is a low, scrubby palm that grows in the coastal plain of Florida and other southeastern states. Its fan-shaped leaves have sharp saw-toothed edges that give the plant its name. Dense clumps of saw palmetto can form an impenetrable thicket. The abundant 2 cm long berries are harvested from the wild in the fall and are dried for medicinal use. They also serve as a source of nutrition for deer, bears, and wild pigs. 1

History

Native tribes of Florida relied on saw palmetto berries for food; however, Europeans often found the taste of the berries objectionable. 1 While native medicinal use of saw palmetto is not recorded, it was introduced into Western medical practice in the 1870s and was a favorite of Eclectic medical practitioners for prostate and other urologic conditions. Saw palmetto berries were official in the US Pharmacopeia in 1906 and 1916, and in the National Formulary from 1926 to 1950. While use in the US declined after that time, saw palmetto has long been a staple phytomedicine in Europe. Recent interest has been rekindled, and saw palmetto is currently ranked in the top 10 herbal products in the US. 2 It is primarily used for its activity in benign prostatic hyperplasia (BPH).

Chemistry

Saw palmetto berries contain large quantities of beta-sitosterol and other plant sterols, 3 as well as free and esterified fatty acids. 4 Most standardized commercial preparations are “liposterolic” extracts containing nonpolar constituents such as fatty acids and sterols, produced either by conventional hexane extraction or by supercritical carbon dioxide extraction. The fatty acid components have been quantitated by gas chromatography 5 and supercritical fluid chromatography, 6 while the alcohols and sterols have been analyzed by TLC and electrospray mass spectrometry of ferrocenyl derivatives. 7 An acidic polysaccharide has been isolated from saw palmetto fruit that had anti-inflammatory activity. 8 , 9

Saw Palmetto Uses and Pharmacology

Saw palmetto's mechanism of action in suppressing the symptoms of BPH is poorly understood. Several animal and human in vitro studies have lead to some hypotheses.

The leading hypothesis involves the inhibition of testosterone 5-alpha reductase, an enzyme that converts testosterone to 5-alpha-testosterone in the prostate. Hexane extracts of saw palmetto were found to inhibit the enzyme from human foreskin fibroblasts, while they had no direct effect on androgen receptor binding. 10 Investigators found various saw palmetto extracts to be much weaker 5-alpha reductase inhibitors in vitro than the synthetic drug finasteride. 11 Similarly, in humans, serum levels of dihydrotestosterone (DHT) were reduced markedly by finasteride, but not by saw palmetto. 12

Further studies using both known 5-alpha reductase isozymes found that finasteride inhibited only type 1 reductase, while saw palmetto inhibited formation of all testosterone metabolites in both cultured prostate epithelial cells and fibroblasts. 13 A different saw palmetto extract, IDS 89, dose dependently inhibited 5-alpha reductase in both the stroma and epithelium of human BPH tissue. This inhibition was related to the free fatty acids present in the extract. 14 A tracer study found that radiolabeled oleic acid in saw palmetto extract was taken up preferentially by rat prostate compared with other tissues. 15 Studies in a coculture model of human prostate epithelial cells and fibroblasts found that saw palmetto inhibited both type 1 and type 2 isoforms of 5-alpha reductase without altering the secretion of prostate-specific antigen. 16 Other recent work has shown that saw palmetto extract inhibits trophic as well as androgenic effects of prolactin in a rat model of prostatic hyperplasia. 17 Structure-activity studies of pure fatty acid inhibition of steroid 5-alpha reductase have found gamma-linolenic acid to be the most potent and specific inhibitor of the enzyme. 18 It is possible that the C ₁₈ monounsaturated fatty oleic acid found in saw palmetto is partly responsible for the observed effects on 5-alpha reductase, though more extensive analysis of saw palmetto fatty acids is required.

There is less support for other hormonal mechanisms. One study found 5-alpha reductase inhibition and inhibition of DHT binding to androgen receptors, 19 and another study demonstrated inhibition of DHT and testosterone receptor binding. 20 Administration of saw palmetto extract over 30 days led to no changes in plasma levels of testosterone, follicle stimulating hormone, or luteinizing hormone. 21 Hormonal pathways were invoked to explain reduced prostate weights in castrated rats treated with estradiol, testosterone, and saw palmetto extract as opposed to estradiol and testosterone alone. 22 In the human prostate cancer line LNCaP, saw palmetto induced a mixed proliferative/differentiative effect that was not seen in the nonhormone-responsive PC3 human prostate cancer cell line. 23 Treatment of patients for 3 months with saw palmetto preceding prostatectomy caused a reduction in DHT levels in BPH tissue along with a corresponding rise in testosterone levels. A marked reduction in epidermal growth factor concentration was also observed in the periurethral region of the prostate. 24

Other observations of saw palmetto extracts include a spasmolytic effect on rat uterus which was suggested to be because of effects on cyclic AMP and calcium mobilization, 25 an inhibition of smooth muscle contraction in rat deferens, guinea pig ileum, and bladder postulated as alpha-adrenoreceptor antagonistic, 26 shown by others to be noncompetitive in nature, 27 and interference with 5-lipoxygenase metabolites in neutrophils. 28

Although the mechanism of action of saw palmetto is not completely understood, clinical trials in BPH have shown convincing evidence of moderate efficacy. A 6-month, double-blind, head-to-head study vs finasteride in 1098 men found equivalent efficacy and a better side effect profile for saw palmetto. 29 Likewise, a 3-year study of IDS 89 in 435 BPH patients found clear superiority to placebo in reduction of BPH symptoms. 30 A 1-year study of 132 patients comparing 2 dose levels of saw palmetto demonstrated efficacy in symptom reduction but little difference between dose levels. 31 The general consensus has been that saw palmetto extracts reduce BPH symptoms without reducing prostate size, therefore delaying surgical intervention. 32 A meta-analysis that included a total of 18 clinical trials in BPH concluded that saw palmetto was better tolerated than finasteride and equivalent in efficacy. 33 A clinical trial in BPH of the saw palmetto constituent beta-sitosterol showed similar efficacy to that seen with saw palmetto itself. 34

Dosage

The crude saw palmetto berries usually are administered at 1 to 2 g/day; however, lipophilic extracts standardized to 85% to 95% fatty acids in soft native extract or 25% fatty acids in a dry extract are more common. Some of the brand name products include Permixon ( Pierre Fabre Medicament ), Prostaserene ( Indena ) SCF extract, Prostagutt (WS 1473, Schwabe ), Remigeron ( Schaper & Brummer ), IDS 89 ( Strathmann AG ), Quanterra Prostate ( Warner Lambert ), and LG 166/S ( Lab. Guidotti ). Typical doses of standardized extracts range from 100 to 400 mg given twice daily for benign prostatic hypertrophy. 21 , 25 , 35 , 36 , 37 , 38

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

Two men stabilized on warfarin experienced an increase in the international normalized ratio (INR) after taking an herbal combination containing cucurbita, saw palmetto, and vitamin E. 39 In both patients, the INR returned to previous values when the herbal product was discontinued. Although neither cucurbita nor saw palmetto can be ruled out as the cause of the increase in INR, it is more likely that vitamin E interfered with vitamin K-dependent clotting factors, adding to the anticoagulant effects of warfarin.

Adverse Reactions

Saw palmetto products are generally well tolerated, with occasional reports of adverse GI effects. Its antiandrogenic activity suggests that it should not be used in pregnancy.

Because of well-documented antiandrogen and antiestrogenic activity, avoid taking with any hormone therapy including oral contraceptive and hormone replacement therapy.

Toxicology

Research reveals little or no information regarding toxicology with the use of saw palmetto.

Bibliography

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