Saw Palmetto

Saw Palmetto

Common Names

  • American dwarf palm tree
  • Cabbage palm

For Patients & Caregivers

Saw palmetto was shown in some studies to help relieve the symptoms of benign prostatic hypertrophy (BPH), but it has not been shown to prevent or treat prostate cancer.

Studies in the laboratory and in animals show that saw palmetto works by countering the effects of androgens (the male sex hormones), such as testosterone and DHT. It is thought that saw palmetto does not reduce the levels of these hormones circulating in the blood, but causes body tissues (like the prostate) to take in lower levels of the hormones. Other studies have noted that saw palmetto reduces the conversion of testosterone to the DHT, its more potent form, by inhibiting the enzyme 5 alpha reductase. Saw palmetto berry extracts also reduce inflammation and edema in laboratory studies by inhibiting the formation of compounds that cause these reactions.

In a lab study, saw palmetto extract was found to slow the growth of normal prostate cells and increase their sensitivity to radiation, while not affecting prostate cancer cells. Since this may increase the risk of complications, patients should consult with a physician before using saw palmetto supplements during radiation therapy.

  • To treat benign prostatic hypertrophy (BPH)
    Several clinical trials and meta-analyses have shown that saw palmetto improves urinary tract symptoms associated with BPH.
  • To treat prostate cancer
    Saw palmetto shows anti-inflammatory and anti-androgen properties in laboratory studies and reduces the levels of DHT in the prostate in clinical trials.
  • As a diuretic
    No scientific evidence supports this use.
  • As an anti-inflammatory
    Laboratory studies support this use, but human data are lacking.
  • You are taking warfarin or other blood thinners: Saw palmetto may increase the risk of bruising and bleeding.
  • You are taking drugs that are substrates of UGT (Uridine 5’-diphospho-glucuronosyltransferase) enzymes: Saw palmetto may increase the risk of side effects of these drugs.
  • You are taking drugs that are substrates of CYP4503A4, 2D6, and 2C9: Saw palmetto may increase the risk of side effects of these drugs.
  • Gastrointestinal complaints: nausea, vomiting, and diarrhea
  • Additive anticoagulant effects and prolonged bleeding time

Case reports of

  • Severe intraoperative hemorrhage
  • Hematuria and coagulopathy
  • Acute pancreatitis
  • Severe liver damage
  • Hot flashes and possibly-related subsequent first menstrual cycle in an 11-year-old girl

In a recent study, 37 saw palmetto-containing supplements were tested using DNA barcoding. A few of these contained related species that cannot be legally sold as herbal dietary supplements in the US, and the identity of several of the other supplements tested remains inconclusive.

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For Healthcare Professionals

Serenoa repens

Saw palmetto is a small slow-growing palm native to southeastern United States. The fruits are a rich source of fatty acids and phytosterols and have been used to promote urination, reduce inflammation, and for treatment of prostatic conditions such as benign prostatic hyperplasia (BPH).

Saw palmetto has been studied in many controlled clinical trials. Whereas data from some studies indicate that it improves lower urinary tract symptoms in patients with benign prostatic hyperplasia (2) (3) (4) (5) (15) (17) (18) (26), conflicting data suggest no such effects (6) (14) (19) (28). In another study, a saw palmetto extract did not affect the serum prostate specific antigen more than placebo, even at high doses (30). However, saw palmetto may benefit patients with chronic bacterial prostatitis when coadministered with Urtica dioica, curcumin and quercitin (16). Along with selenium and lycopene, it exerts anti-inflammatory effects (31). Pretreatment with saw palmetto reduced intra- and postoperative complications in patients who underwent transurethral resection of the prostate and open prostatectomy (22).

A saw palmetto extract was found to inhibit growth of normal prostate cells and increase their sensitivity to radiation in vitro, but did not affect malignant prostate cancer cells (20). A large epidemiologic study did not find associations with the use of saw palmetto and reduced risk of prostate cancer (27).

Due to the increased risk of normal tissue complications, patients should consult with a physician before using saw palmetto supplements during radiation therapy. There is an ongoing study to determine the effects of saw palmetto on symptom management during radiation therapy (32).

In a recent study of 37 saw palmetto-containing supplements tested using DNA barcoding, 6% contained related species that cannot be legally sold as herbal dietary supplements in the US and the identity of 9% of supplements tested remains inconclusive (33).

  • Benign prostatic hypertrophy (BPH)
  • Inflammation
  • Promote urination
  • Prostate cancer

Studies with a liposterolic extract of saw palmetto berries showed that it reduced the uptake by tissue specimens of both testosterone and dihydrotestosterone (DHT) by more than 40% suggesting antiandrogenic activity (7). Further, the extract inhibited binding of DHT to its receptor (8) and blocked the conversion of testosterone to DHT by inhibiting the activity of 5-alpha-reductase (9). The berries also inhibit cyclooxygenase and 5-lipoxygenase pathways, thereby preventing the biosynthesis of inflammation-producing prostaglandins and leukotrienes (10).

GI complaints, nausea, vomiting, and diarrhea

Case reports

  • Intraoperative hemorrhage, anticoagulant effects and prolonged bleeding time (11)
  • Hematuria and coagulopathy (21)
  • Acute pancreatitis in a 65-year-old man: following use of saw palmetto for 1 week before onset of symptoms. His condition improved after treatment and avoiding saw palmetto (23).
  • Severe liver damage in a 58-year-old man: following consumption of saw palmetto to alleviate BPH symptoms (24).
  • Hot flashes and possibly-related subsequent first menstrual cycle in an 11-year-old girl (35).
  • Anticoagulants: Saw palmetto may have additive anticoagulant effect (11).
  • UGT (Uridine 5’-diphospho-glucuronosyltransferase) substrates: Saw palmetto inhibits UGT enzymes in vitro and can increase the side effects of drugs metabolized by them (25).
  • CYP 450 substrates: Saw palmetto inhibits cytochrome P450 3A4, 2D6, and 2C9 and may interfere with the actions of drugs metabolized by these enzymes (29).
  • May prolong bleeding time (11)
  • No significant change in mean serum PSA noted (3)

  1. Fagelman E, Lowe FC. Herbal medications in the treatment of benign prostatic hyperplasia (BPH). Urol Clin N Am 2002;29:23-9.

  2. Bent S, et al. Saw palmetto for benign prostatic hyperplasia. N Engl J Med 2006;354(6): 557-566.

  3. El-Sheikh MM, Dakkak MR, and Saddique A. The effect of Permixon on androgen receptors. Acta Obstet Gynecol Scand. 1988;67(5):397-9.

  4. Goldmann WH, Sharma AL, Currier SJ, et al. Saw palmetto berry extract inhibits cell growth and Cox-2 expression in prostatic cancer cells. Cell Biol Int 2001;25:1117-24.

  5. Newall C, Herbal Medicines: A Guide for Health-Care Professionals. London: Pharmaceutical Press; 1996.

  6. Avins AL, Bent S, Staccone S, et al. A detailed safety assessment of a saw palmetto extract.Complement Ther Med. 2008 Jun;16(3):147-54.

  7. Tacklind J, MacDonald R, Rutks I, Wilt TJ. Serenoa repens for benign prostatic hyperplasia. Cochrane Database of Systematic Reviews 2009, Issue 2. Art. No.: CD001423. DOI: 10.1002/14651858.CD001423.pub2.

  8. Hasan Y, Schoenherr D, Martinez AA, et al. Prostate-specific natural health products (dietary supplements) radiosensitize normal prostate cells. Int J Radiat Oncol Biol Phys. 2010 Mar 1;76(3):896-904.

  9. Villanueva S, González J. Coagulopathy induced by saw palmetto: a case report. Bol Asoc Med P R. 2009 Jul-Sep;101(3):48-50.

  10. Anceschi R, Bisi M, Ghidini N, Ferrari G, Ferrari P. Serenoa repens (Permixon) reduces intra- and postoperative complications of surgical treatments of benign prostatic hyperplasia. Minerva Urol Nefrol. 2010 Sep;62(3):219-23.

  11. Wargo KA, Allman E, Ibrahim F. A possible case of saw palmetto-induced pancreatitis. South Med J. 2010 Jul;103(7):683-5.

  12. Lapi F, Gallo E, Giocaliere E, et al. Acute liver damage due to Serenoa repens: a case report. Br J Clin Pharmacol. 2010 May;69(5):558-60.

  13. Mohamed ME, Frye RF. Inhibitory Effects of Commonly Used Herbal Extracts on UGT1A4, 1A6, and 1A9 Enzyme Activities. Drug Metab Dispos. 2011 Jun 1. [Epub ahead of print]

  14. Sinescu I, Geavlete P, Multescu R, et al. Long-term efficacy of Serenoa repens treatment in patients with mild and moderate symptomatic benign prostatic hyperplasia. Urol Int. 2011;86(3):284-9. Epub 2011 Feb 8.

  15. Brasky TM, Kristal AR, Navarro SL, et al. Specialty supplements and prostate cancer risk in the VITamins and Lifestyle (VITAL) cohort. Nutr Cancer. 2011 May;63(4):573-82.

  16. Barry MJ, Meleth S, Lee JY, et al. Effect of Increasing Doses of Saw Palmetto Extract on Lower Urinary Tract Symptoms. A Randomized Trial. JAMA. 2011;306(12):1344-1351.

  17. Saw Palmetto: Symptom Management for Men During Radiation Therapy. Accessed December 19, 2013.

  18. Little DP, Jeanson ML. DNA barcode authentication of saw palmetto herbal dietary supplements. Sci Rep. 2013 Dec 17;3:3518.

  19. Miroddi M, Carnì A, Mannucci C, et al. Hot flashes in a young girl: a wake-up call concerning Serenoa repens use in children. Pediatrics. 2012 Nov;130(5):e1374-6.

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