Saw Palmetto

Synonyms: Serenoa repens, Sabal serrulata, American dwarf palm tree

This supplement has been proposed for the following purposes or treating the following conditions. Also given is the current scientific support for use (on a scale of 0-10). Note that a low rating does not necessarily indicate that a supplement does not work, just that research is either unavailable or has not demonstrated a benefit.

Benign prostatic hyperplasia - 10
Chronic prostatitis - 4
Prostate cancer – 4
Hair loss prevention – 2

Benefits of Supplementation

Saw palmetto is a small, shrubby, palmlike plant found in North America and the West Indies [1-3]. It is found primarily in the coastal and southeastern regions of the US from the Carolinas to Florida and also in California [3-4]. Herbal extracts are derived from the dried berry of the plant [2, 4]. There are a number of extracts available, and the solvents used include ethanol, methanol, liquid carbon dioxide, and hexane. The form most widely studied form is Permixon, a hexane extract [4]. The extracts can contain many compounds, including both free and esterfied saturated and unsaturated fatty acids such as lauric, myristic, palmitic, oleic, capric, caprylic, linoleic, linolenic, and stearic acids, flavanoids, and phytosterols such as beta-sitosterol, campesterol, and stimasterol. The fatty acids usually make up the majority of the extract (80-90%), with only a small portion being other compounds [1, 5].

Saw palmetto is most commonly used to treat benign prostatic hyperplasia (BPH). This condition, which involves nonmalignant growth of the prostate gland, is very common and affects over 50% of men aged 60 or older and 90% of men aged 70 or older [1, 6]. Although aging and ethnicity are the primary risk factors (with a lower incidence in Asians), physical inactivity may be another risk factor [7]. Use of anabolic steroids can also cause prostate swelling, and for this reason many steroid users self-medicate with saw palmetto in the hopes that it will prevent this effect [8]. Saw palmetto is the most widely used self-prescribed treatment for BPH [1]. It is commonly used in both Europe and Japan, and is used in 50% of BPH cases in Italy and 90% in Germany [4, 6].

Many clinical trials have been conducted on the use of saw palmetto extract in the treatment of BPH. A meta-analysis published in 2004 in BJU International pooled the results of 17 clinical trials on Permixon involving 4280 patients and lasting three weeks to two years. It found that Permixon was associated with a mean reduction in the International Prostate Symptom Score and other measured symptoms of BPH compared to placebo [9]. Other meta-analyses have had similar conclusions [5]. Trials as long as five years have found a benefit from saw palmetto, and multiple extracts have been tested and found to be of benefit [10-11]. Overall, there is very strong evidence for symptomatic improvement in patients with BPH from saw palmetto.

Other common therapies for BPH include prescription alpha blockers and 5alpha-reductase inhibitors (most notably finasteride or Proscar). In a 1-year trial comparing saw palmetto extract with the alpha1 antagonist tamsulosin, tamsulosin had a faster onset of action but ultimately the treatments were equally effective and tamsulosin caused more side effects [12-13]. A newer study in the June 2004 issue of European Urology found that saw palmetto was slightly superior to tamsulosin [14]. The benefits of these two are not additive, as another study found no difference in patients treated with tamsulosin vs. patients treated with both tamsulosin and saw palmetto for one year [12]. Saw palmetto was also compared to the alpha1 antagonist alfuzosin in a 3 week trial and alfuzosin was superior, but this may be explainable by the faster onset of action [12].

Other research has compared saw palmetto with finasteride. A meta-analysis found that saw palmetto is as effective as finasteride in the treatment of BPH with fewer side effects [15]. Animal models indicate that saw palmetto may also be specifically more effective than finasteride in androgen-independent prostate growth [16]. Finasteride can interfere with prostate cancer screening by changing prostate-specific antigen (PSA) levels, and saw palmetto is less likely to have this effect [17]. One review argues that saw palmetto should be the first-line therapy in the treatment of BPH because of the low cost compared to other options, strong evidence for effectiveness, and excellent safety profile [15].

Saw palmetto is also promoted for treating other prostate conditions, but there is considerably less evidence for other uses at present. Self-medication with saw palmetto to treat both chronic prostatitis and prostate cancer is common [1, 4]. It has been pointed out that some of the BPH trials probably included patients with chronic prostatitis because the symptoms are similar [18]. However, one trial (not published) compared saw palmetto and finasteride in the treatment of chronic nonbacterial prostatitis and found improvement in the finasteride group but not the saw palmetto group [2]. Many in vitro studies have found saw palmetto to inhibit prostate cancer cell growth [1]. However, studies in live animals are still lacking.

Other promoted uses of saw palmetto include sexual enhancement, acne treatment, and hair loss prevention. There is presently little evidence for any of these uses. One small pilot study found greater improvement in males with androgenic alopecia with saw palmetto and beta-sitosterol compared to placebo. However, no statistical analysis was done, and the results may have been due to chance [19].

In all clinical trials, saw palmetto has been associated with very few side effects or changes in laboratory parameters [4]. It does not affect sexual function as finasteride does [11]. Although some trials report gastric upset, this does not occur with a higher incidence than placebo, while another source said that this effect may occur, but not if the saw palmetto is taken along with food [3-4, 15]. There are no known drug interactions, nor does it interact with the main drug metabolizing enzymes in humans [4-5]. In a toxicological study, dogs were fed 2 g/kg daily of saw palmetto for six months and no adverse effects were observed [4].

Mechanism of Action

Although the evidence for the effectiveness of saw palmetto in treating BPH is strong, the mechanism of action is still being debated. The most well known is inhibition of 5alpha-reductase (5AR). 5AR is the enzyme that catalyzes the conversion of testosterone to dihydrotestosterone (DHT), and DHT is associated with prostate growth [6]. Finasteride is a potent inhibitor of 5AR type II, while saw palmetto inhibits both type I and type II, but is less potent [9, 15].

What is interesting about the 5AR inhibition caused by saw palmetto is that it is prostate-specific. Not only does saw palmetto inhibit both types of 5AR in the prostate but not in other tested tissues (epididymis, testes, kidney, skin, and breast) in vitro [20], the active ingredients of saw palmetto concentrate in the prostate as opposed to other tissues after oral administration to rats [21]. This is in line with human studies indicating that saw palmetto extract preferentially reduces prostatic DHT and does not alter plasma DHT or sex hormone levels [9, 22-23]. This explains the lack of side effects in clinical trials. It also means that saw palmetto is unlikely to prevent hair loss.

Since saw palmetto is a less potent inhibitor of 5AR than finasteride but is equally effective in the treatment of BPH, it is likely that it has other mechanisms of action. For one, saw palmetto has also been reported to inhibit DHT binding to the androgen receptor in prostate tissue [1, 6]. Saw palmetto has also been reported as an alpha1 antagonist in vitro [24]. A study finding that saw palmetto did not affect cardiovascular variables in humans concluded that saw palmetto was not an alpha1 antagonist in vivo, but this study did not take into account that saw palmetto may concentrate in the prostate, so whether or not this is an important mechanism is still in question [25]. Other possible mechanisms supported by some research include inhibition of prolactin-induced cell proliferation, antiestrogenic activity, antiinflammatory effects, and inhibition of growth factors [1, 6, 9, 24]. The fact that saw palmetto inhibits lipooxygenase and cyclooxygenase is one of the reasons it may prove to be beneficial in treating chronic prostatitis [2].

The component or mixture of components responsible for the effects of saw palmetto has not yet been established [4]. It is likely that the biological effects of saw palmetto could only be explained by a combination of ingredients [1]. Some studies indicate that the free fatty acids may be primarily responsible for some of its activities, including 5AR inhibition [26-27]. Although it is commonly assumed that beta-sitosterol is the primary active ingredient in saw palmetto, there is presently little research to support this, and beta-sitosterol does not share many of the biological activities of saw palmetto (such as alpha1 antagonism) [28].

Recommended Dosage & Products

Most clinical trials have used 320 mg daily of Permixon. A dosage of 480 mg did not have any advantage over 320 mg in a six month study [4]. Another three month study compared 320 mg once daily and 160 mg twice daily and found that both treatments were equally effective, so it should only be necessary to take saw palmetto once a day [29]. After supplementation has begun, symptomatic reduction can be expected in 2-12 weeks [3].

One study found that saw palmetto supplements from some brands did not meet label claims [30]. For this reason, it is important to use a reliable brand. Now Saw Palmetto is recommended, and it has been tested by a third party (Consumer Lab) and met label claims.

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