About Herbs

Bottom Line: Saw palmetto can help relieve the symptoms of benign prostatic hypertrophy (BPH), but there is no proof that it can prevent or treat prostate cancer. Some saw palmetto supplements may contain far less than the labelled amount.

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.

Benign prostatic hypertrophy (BPH)
Two hundred and twenty-five men (over the age of 49 years) with moderate-to-severe symptoms of benign prostatic hyperplasia (BPH) were given saw palmetto extract (160 mg twice a day) or placebo for one year. There was no significant difference in the American Urological Association Symptom Index (AUASI) scores or the maximal urinary flow rates between patients taking saw palmetto or placebo. Also, no significant differences were observed in prostate size, quality of life, or serum prostate specific antigen (PSA) levels between the two groups.

In an evaluation of men with symptomatic BPH, 20 men taking saw palmetto were compared to 20 men receiving placebo and 15 men receiving finasteride. The levels of androgens (testosterone and DHT) in their prostate tissue were measured at the start and end of the study. Finasteride reduced levels of both testosterone and DHT, while saw palmetto was found to reduce DHT levels by 32%, a modest but significant amount.

A meta-analysis of all published clinical trials using saw palmetto for the treatment of benign prostatic hypertrophy (BPH) was conducted. Eleven randomized clinical trials and two open label trials were evaluated, overall showing a significant improvement in peak urination flow rate and reduction in nocturia (needing to urinate at night) in saw palmetto patients compared to placebo.

In a meta-analysis of the effect of saw palmetto on benign prostatic hypertrophy (BPH), 18 randomized, controlled trials conducted between 1966 and 1997 were analyzed. Compared to men receiving placebo, men treated with saw palmetto reported a decrease in urinary tract symptoms. Compared with men receiving finasteride, men treated with saw palmetto had similar improvements in urinary tract symptoms. Side effects from saw palmetto were mild and infrequent; erectile dysfunction was more frequent with finasteride.

Serenoa repens

Saw, Sabal serulata, Sabalis serulata, palmetto berry, American dwarf palm tree, cabbage palm

Derived from the berry of the plant. Saw palmetto is used primarily for symptoms related to prostatic conditions such as benign prostatic hypertrophy (BPH) ^{(6) (7)}. It is thought to have anti-androgenic and anti-inflammatory properties. Results from earlier clinical studies suggested that saw palmetto can improve urinary flow rate and reduce nocturia in patients with benign prostatic hyperplasia ⁽¹²⁾. However, a recent randomized clinical trial showed saw palmetto is no better than placebo for improving BPH-associated symptoms ⁽¹⁴⁾. Reported adverse effects include nausea and vomiting, diarrhea and intraoperative hemorrhage ^{(2) (9)}.

The mechanism of action is antiandrogenic. Studies have shown that a liposterolic extract of the berries reduced the uptake by tissue specimens of both testosterone and DHT(dihydrotestosterone)  by more than 40%. This mechanism is confirmed by the observation that saw palmetto extract does not induce changes in the level of testosterone or other hormones in the plasma itself. Other studies have noted that it reduces the conversion of less active testosterone to the more active DHT by inhibiting the enzyme steroid 5 alpha reductase. In addition to their antiandrogenic properties, anti-inflammatory and antiedematous activities have all been demonstrated in the berries. This apparently results from inhibition of the cyclooxygenase and 5-lipoxygenase pathways thereby preventing the biosynthesis of inflammation-producing prostaglandins and leukotrienes.
^{(3) (8)}

Analysis of saw palmetto components including lauric acid, oleic acid, and beta-sitosterol in rats revealed wide distribution. Highest concentrations were found in abdominal fat, prostate, and skin, while lesser amounts were found in bladder and liver.
⁽⁴⁾

There is a reported case of severe intraoperative hemorrhage after consumption of saw palmetto. The prolonged bleeding in this patient was thought to be a result of saw palmetto's cyclooxygenase inhibition effect that lead to platelet dysfunction.
A recent laboratory evaluation of six commercially available brands of saw palmetto revealed actual fatty acid content to vary considerably from the labeled dosage, as has been found for many herbal products previously studied, from 3% to +240%. Three brands contained less than 20% of the stated amount. The authors recommend that patients who have not responded to over-the-counter saw palmetto try a second brand.
⁽²⁾

Infrequent: Intraoperative hemorrhage, GI complaints, nausea, vomiting, and diarrhea
⁽⁹⁾

Anticoagulants: Saw palmetto may have additive anticoagulant effect.
⁽⁹⁾

May prolong bleeding time ⁽⁹⁾.
No significant change in mean serum PSA noted ⁽¹⁰⁾.

Over 100 open, controlled and comparative trials have been conducted on saw palmetto.

Bent S, et al. Saw Palmetto for Benign Prostatic Hyperplasia. N Engl J Med 2006; 354(6): 557- 566.
Two hundred and twenty-five men (over the age of 49 years) with moderate-to-severe symptoms of benign prostatic hyperplasia (BPH) were randomized to receive saw palmetto extract (160 mg twice a day) or placebo for one year. There was no significant difference in the primary outcome measures -- the American Urological Association Symptom Index (AUASI) scores or the maximal urinary flow rates between patients taking saw palmetto or placebo. Also, no significant differences were observed in prostate size, residual volume after voiding, quality of life, or serum PSA levels between the two groups.
These data contradict several earlier studies in which saw palmetto appeared to be a promising alternative for BPH. Researchers point to the methodologic flaws in those studies, including shorter duration of study, failure to use validated symptom scores, and ineffective blinding.

Marks LS, et al. Tissue effects of saw palmetto and finasteride: use of biopsy cores for in situ quantification of prostatic androgens. Urology 2001;57:999-1005.
Baseline androgen values were measured in surgically excised prostatic tissues. For control versus finasteride-treated men, tissue androgen values obtained with needle biopsy specimens were similar both for absolute values and percentage of change to those previously reported. Saw palmetto was found to induce suppression of prostatic DHT levels a modest but significant amount, supporting the hypothesis that inhibition of the enzyme 5-alpha reductase is a mechanism of action of this substance.

Boyle P, et al. Meta-analysis of clinical trials of permixon (saw palmetto) in the treatment of symptomatic benign prostatic hyperplasia. Urology 2000;55:533-9.
All published clinical trial data on Permixon (saw palmetto) for the treatment of benign prostatic hypertrophy (BPH) consists of 11 randomized clinical trials and 2 open label trials involving 2,859 patients. This meta-analysis of all available published trials revealed a significant improvement in peak flow rate and reduction in nocturia in Permixon patients compared to placebo. Wilt TJ, et al. Saw palmetto extracts for treatment of benign prostatic hyperplasia: a systematic review.

JAMA 1998;280:1604-9. Studies were identified through Medline (1966-1997).
A total of 18 randomized, controlled trials involving 2,939 men met inclusion criteria and were analyzed. Treatment allocation concealment was adequate in 9 studies; 16 were double-blind. The mean study duration was 9 weeks. Compared to men receiving placebo, men treated with saw palmetto had decreased urinary tract symptom scores and improvement in self-rating of urinary tract symptoms. Compared with men receiving finasteride, men treated with saw palmetto had similar improvements in urinary tract symptom scores. Adverse effects due to saw palmetto were mild and infrequent; erectile dysfunction was more frequent with finasteride.