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Saw Palmetto

Saw palmetto, also called sabal palm, grows in the southeastern United States. Its dark berries were traditionally made into a tea and taken for urinary problems or sexual difficulties.

During much of the nineteenth century, saw palmetto berry extract was included in the National Formulary, a list of acceptable medicines, to treat the symptoms of prostate enlargement. As medicine came to rely more on science, doctors became skeptical about the value of this botanical remedy and it was dropped from the Formulary before 1950.

More recent studies indicate that it is indeed effective for this indication and probably should never have been dropped.

Even men who have saw palmetto growing in their backyards may want to stick with commercial extracts rather than try to make their own tea. The berries do not taste good, and most of the active ingredients appear to be less soluble in water than in alcohol or hexane.

Active Ingredients

Saw palmetto berries contain free fatty acids and plant sterol compounds described as phytosterols or sitosterols, especially beta-sitosterol and some related chemicals. These ingredients appear to modify estrogen receptors and block the conversion of testosterone to dihydrotestosterone (DHT), a more active chemical.

There are also flavonoids and some polysaccharides in the berries, but their activity has not been described. Standardized products contain 85 to 95 percent fatty acids and sterols.


At least seven controlled studies demonstrate that saw palmetto berry extract is better than placebo for treating symptoms of benign prostate hypertrophy (frequent urination, restricted urine flow, nighttime urination).

In one study, the herb was nearly as effective as the prescription drug Minipress (prazosin) for controlling such symptoms, and in other research it reportedly performed better than the prescription prostate medicine Proscar (finasteride) in reducing symptoms.

Research using ultrasound has shown that saw palmetto berry extract can shrink enlarged prostate tissue.
Animal research has shown that saw palmetto berries may also have anti-inflammatory activity and can help reduce allergic reactions.

The plant has been used traditionally as a diuretic and may also help to stimulate immune response.

The herb’s effect on enlarged prostate tissue is by far the most clinically important.


For early stages of benign prostate enlargement: 320 mg extract daily, in divided doses, or the equivalent of 1 or 2 grams of saw palmetto berries.

Four to six weeks may be required to determine if the herb is helping.

A standardized product used in Germany is available in the United States under the brand name ProstActive.

Special Precautions

Estrogen-like activity and the ability to block testosterone conversion suggest that pregnant women and those who may become pregnant should avoid contact with saw palmetto berry extract, just as they should avoid finasteride.

Men are urged not to treat urinary symptoms without medical diagnosis. Similar symptoms might be caused by a more serious condition, such as prostate cancer, that will not benefit from herbal treatment.

Adverse Effects

Side effects are uncommon, although a few men have reported upset stomach or headache.

At high doses saw palmetto berries or extract may trigger diarrhea or raise blood pressure. Most adverse effects are mild.

Saw palmetto berry extract very rarely causes impotence or lowers libido as Proscar occasionally does.

Possible Interactions

Because saw palmetto berries have both estrogenic and antiestrogenic activity, they are not recommended for women using female hormones for contraception or hormone replacement therapy.

Common sense would also suggest that men taking Proscar or Propecia, drugs that act in a similar manner to saw palmetto berry extract, should avoid the herbal product except under a physician’s recommendation and monitoring.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.”.
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