Saw palmetto (Serenoa repens , Sabal serrulata) is used popularly in Europe for symptoms associated with benign prostatic hypertrophy (enlargement of the prostate). Although not considered standard of care in the United States, it is the most popular herbal treatment for this condition.
Historical use of saw palmetto can be traced in the Americas to the Mayans who used it as a tonic and to the Seminoles who took the berries as an expectorant and antiseptic.
Saw palmetto was listed in the United States Pharmacopeia from 1906 to 1917 and in the National Formulary from 1926 to 1950. Saw palmetto extract is a licensed product in several European countries.
Multiple mechanisms of action have been proposed, and saw palmetto appears to possess 5-α-reductase inhibitory activity (thereby preventing the conversion of testosterone to dihydrotestosterone). Hormonal/estrogenic effects have also been reported, as well as direct inhibitory effects on androgen receptors and anti-inflammatory properties.
NB! The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.
Adults (18 years and older)
For enlarged prostate (benign prostatic hypertrophy), a dose of 320 milligrams daily, in one dose or two divided doses (80% to 90% liposterolic content), has been used in numerous studies. Reports suggest that 160 milligrams once daily may be as effective as twice daily.
Traditional or other suggested doses that are less studied include: 1 to 2 grams of ground, dried, or whole berries daily; 2 to 4 milliliters of tincture (1:4) three times daily; 1 to 2 milliliters fluid extract of berry pulp (1:1) three times daily; or tea (2 teaspoons dried berry with 24 ounces water, simmered slowly until liquid is reduced by half) taken as 4 ounces three times daily. Teas prepared from saw palmetto berries are potentially not as effective because the active ingredients may not dissolve in water. Some experts believe that a preparation called lipidosterolic extract of Serenoa repens (LSESR) may cause fewer side effects.
Children (younger than 18 years)
Not enough information is available to recommend the use of saw palmetto in children.
NB! There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.
Few allergic symptoms have been reported with saw palmetto. A study of people taking the combination product PC-SPES® (no longer commercially available), which includes saw palmetto and seven other herbs, reports that three out of 70 people developed allergic reactions. In one case, the reaction included throat swelling and difficulty breathing.
Side Effects and Warnings
Few severe side effects of saw palmetto are noted in the published scientific literature. The most common complaints involve the stomach and intestines, and include stomach pain, nausea, vomiting, bad breath, constipation, and diarrhea. Stomach upset caused by saw palmetto may be reduced by taking it with food. Some reports suggest that there may be less abdominal discomfort with the preparation lipidosterolic extract of Serenoa repens (LSESR). A small number of reports describe ulcers or liver damage and yellowing of the skin (jaundice), but the role of saw palmetto is not clear in these cases. Similarly, reports of headache, dizziness, insomnia, depression, breathing difficulties, muscle pain, high blood pressure, chest pain, abnormal heart rhythm, and heart disease have been reported, but are not clearly caused by saw palmetto. People with health conditions involving the stomach, liver, heart, or lungs should use caution.
Caution is advised in people scheduled to undergo some surgeries or dental work, who have bleeding disorders, or who are taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary.
Some men using saw palmetto report difficulty with erections, testicular discomfort, breast tenderness or enlargement, and changes in sexual desire. Saw palmetto may have effects on the body’s response to the sex hormones estrogen and testosterone, but no specific effect has been well demonstrated in humans. Men or women taking hormonal medications (such as finasteride/Proscar®/Propecia® or birth control pills) or who have hormone-sensitive conditions should use caution. Tinctures may contain high levels of alcohol and should be avoided when driving or operating heavy machinery.
In theory, PSA (prostate specific antigen) levels may be artificially lowered by saw palmetto, based on a proposed mechanism of action of saw palmetto (inhibition of 5-α-reductase). Therefore, there may be a delay in diagnosis of prostate cancer or interference with following PSA levels during treatment or monitoring in men with known prostate cancer.
The combination product PC-SPES®, which contains saw palmetto and seven other herbs, has been found to contain prescription drugs including warfarin, a blood thinner. The U.S. Food and Drug Administration (FDA) has issued a warning not to use PC-SPES® for this reason, and it is no longer commercially available.
Pregnancy and Breastfeeding
Because of possible hormonal activity, saw palmetto extract is not recommended for women who are pregnant or breastfeeding. Many tinctures contain high levels of alcohol and should be avoided during pregnancy.