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Saw Palmetto

Other common name(s): saw palmetto berry extract, shrub palmetto, dwarf palm

Scientific/medical name(s): Serenoa repens


Saw palmetto is a low-growing palm tree found in the West Indies and in coastal regions of the southeastern United States. The tree grows 6 to 10 feet in height and has a crown of large leaves. The berries are used in herbal remedies.


Some clinical studies have found that saw palmetto relieves some symptoms of benign prostatic hyperplasia (BPH), or enlarged prostate, such as difficult and frequent urination. However, at this time there are no available study results that show that saw palmetto can prevent or treat prostate cancer.

How is it promoted for use?

Saw palmetto is promoted for relieving some of the symptoms of BPH, which include difficult and frequent urination. Chemicals in saw palmetto berries called sterols are said to interfere with the ability of hormones such as testosterone to cause prostate cells to grow.

Saw palmetto is sometimes promoted by itself or with other herbs as a treatment for prostate cancer. Saw palmetto is also promoted as a treatment for prostatitis (inflamed prostate gland). Some proponents claim it increases sex drive and fertility and that it can be used to treat low thyroid function.

What does it involve?

Saw palmetto supplements are available as capsules, tablets, extracts, and as a tea. There is no standard dosage. In some clinical studies for the treatment of BPH, patients received 320 milligrams per day as a single dose or divided into 2 doses. A recent study showed wide variation in the contents of different brands of saw palmetto supplements.

What is the history behind it?

Native Americans ate the berries of the saw palmetto believing they served as a tonic that nourished the body, stimulated appetite, and promoted weight gain. They also used the herb to treat problems of the urinary tract and genital system, such as trouble urinating or frequent nighttime urination.

Saw palmetto supplements are very popular in Europe, especially in Germany, where doctors often prescribe them for patients with BPH. Saw palmetto is approved by Commission E (Germany's regulatory agency for herbs) for prostate complaints or irritable bladder. Saw palmetto supplements have become popular in the United States in recent years as well and are often marketed "for prostate health."

What is the evidence?

Some research has found that saw palmetto extract may reduce symptoms of BPH. A review published in 2002 looked at 21 clinical studies on saw palmetto conducted over the last 30 years and involving more than 3,000 patients. The report concluded that saw palmetto provided mild to moderate improvement in urinary symptoms such as frequent nighttime urination and problems with urine flow. The improvements were similar to those seen in men who took the prescription drug finasteride (Proscar®) for BPH. Saw palmetto also caused fewer and milder side effects than finasteride. Whether side effects are long-lasting is unclear. However, a 2006 study of 225 men that carefully evaluated symptoms, maximal urine flow rate, prostate size, and quality of life for one year found that saw palmetto had no effect on any of these outcomes. A recent review concluded that although most studies have suggested improvement in BPH, the precise clinical use of saw palmetto remains undefined. Saw palmetto is not currently recommended in major US or European urology society guidelines for treatment of BPH.

It is important to note, however, that benign prostatic hyperplasia is not cancer. Some laboratory studies in cell cultures and animal studies have hinted that saw palmetto may affect prostate cancer cells (and therefore have potential for prevention or treatment), but others have found no effect. Available scientific studies do not support claims that saw palmetto can prevent or treat prostate cancer in humans. One epidemiologic study of more than 30,000 men, published in 2006, concluded that saw palmetto had no detectable influence on prostate cancer risk. Further research in this area is needed.

Are there any possible problems or complications?

This product is sold as a dietary supplement in the United States. Unlike companies that produce drugs (which must provide the FDA with results of detailed testing showing their product is safe and effective before the drug is approved for sale), the companies that make supplements do not have to show evidence of safety or health benefits to the FDA before selling their products. Supplement products without any reliable scientific evidence of health benefits may still be sold as long as the companies selling them do not claim the supplements can prevent, treat, or cure any specific disease. Some such products may not contain the amount of the herb or substance that is written on the label, and some may include other substances (contaminants). Though the FDA has written new rules to improve the quality of manufacturing processes for dietary supplements and the accurate listing of supplement ingredients, these rules do not take full effect until 2010. And, the new rules do not address the safety of supplement ingredients or their effects on health when proper manufacturing techniques are used.
Most such supplements have not been tested to find out if they interact with medicines, foods, or other herbs and supplements. Even though some reports of interactions and harmful effects may be published, full studies of interactions and effects are not often available. Because of these limitations, any information on ill effects and interactions below should be considered incomplete.

Side effects from saw palmetto are not common but may include headache, nausea, vomiting, upset stomach, dizziness, constipation or diarrhea, trouble sleeping, and fatigue. Its long-term effects and safety have not been studied.

Men who have symptoms that might be caused by BPH, such as difficult, frequent, or urgent urination, should see a doctor as soon as possible, rather than treating themselves with saw palmetto. These symptoms can also result from prostate cancer or other serious conditions, and self-treatment with saw palmetto could delay diagnosis and treatment.

Saw palmetto does not seem to interfere with the measurement of prostate-specific antigen or PSA, a protein made by prostate cells that is used in testing for prostate cancer, although this has not been studied extensively. Since saw palmetto affects testosterone metabolism in the same way as finasteride (which does affect PSA levels), some doctors recommend that men have a baseline PSA test and digital rectal exam before starting treatment with saw palmetto, just to be safe.

Relying on the use of saw palmetto alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.

Additional resources

More information from your American Cancer Society

The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).

Dietary Supplements: What Is Safe?

The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management

Complementary and Alternative Methods and Cancer

Placebo Effect

Learning About New Ways to Treat Cancer

Learning About New Ways to Prevent Cancer


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Saw palmetto. Memorial Sloan-Kettering Cancer Center Web site. Accessed at www.mskcc.org/mskcc/html/69364.cfm on June 6, 2008.

Saw palmetto (serenoa repens [bartram] small). Mayo Clinic Web site. Accessed at www.mayoclinic.com/health/saw-palmetto/NS_patient-sawpalmetto on June 6, 2008.

Sinclair RD, Mallari RS, Tate B. Sensitization to saw palmetto and minoxidil in separate topical extemporaneous treatments for androgenetic alopecia. Australas J Dermatol. 2002;43:311-312.

Wadsworth TL, Worstell TR, Greenberg NM, Roselli CE. Effects of dietary saw palmetto on the prostate of transgenic adenocarcinoma of the mouse prostate model (TRAMP). Prostate. 2007;67:661-673.

Wilt T, Ishani A, Mac Donald R. Serenoa repens for benign prostatic hyperplasia. Cochrane Database Syst Rev. 2002;(3):CD001423.

Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.

Last Medical Review: 11/28/2008
Last Revised: 11/28/2008