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.
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, but there is no proof from clinical trials that saw palmetto can treat prostate cancer.
As a diuretic No scientific evidence supports this use.
As an anti-inflammatory Laboratory studies support this use, but there is no proof from clinical trials that this effect occurs in humans.
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.
This product is regulated by the FDA as a dietary supplement. Unlike approved drugs, supplements are not required to be manufactured under specific standardized conditions. This product may not contain the labeled amount or may be contaminated. In addition, it may not have been tested for safety or effectiveness.
In fact, a recent laboratory evaluation of six commercially available brands of saw palmetto revealed actual content to vary considerably from the labeled dosage, from only 3% to over 240%. Three brands contained less than 20% of the stated amount.
Because of inconsistencies in product labeling, the saw palmetto supplement you are taking may not contain as much active ingredient as it claims. It has been recommended that patients who have not responded to a certain saw palmetto product try a second brand.
Four to six weeks may be necessary to see results.
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 saw palmetto improves urinary flow rate and reduces nocturia in patients with benign prostatic hyperplasia (2)(3)(4)(5)(15)(17)(18), conflicting data suggest no such effects (6)(14). A recent study showed that saw palmetto may benefit patients with chronic bacterial prostatitis when coadministered with Urtica dioica, curcumin and quercitin (16).
A laboratory evaluation of six commercial brands of saw palmetto revealed the actual fatty acid content to vary considerably from the labeled dosage, from 3% to +240%. In addition, three of the brands tested were found to contain less than 20% of the stated amount. Patients should use caution before using over-the-counter saw palmetto products (1).
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).
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. (13)
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. (1)
Although infrequent, saw palmetto may cause intraoperative hemorrhage, GI complaints, nausea, vomiting, and diarrhea. It may also have additive anticoagulant effects and prolong bleeding time (11).
A case of severe intraoperative hemorrhage following consumption of saw palmetto has been reported (11).
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.
Wilt TJ, Ishani A, Start G, et al. Saw palmetto extracts for treatment of benign prostatic hyperplasia: a systematic review. JAMA 1998;280:1604-9. 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.
