Saw palmetto is a native plant of North America, and it is still primarily grown in the United States.
The saw palmetto tree grows only about 2 to 4 feet high, with fan-shaped serrated leaves and abundant berries. Native Americans used these berries for the treatment of various urinary problems in men, as well as for women with breast disorders. European and American physicians took up saw palmetto as a treatment for benign prostatic hyperplasia (BPH). In the 1960s, French researchers discovered that by concentrating the oils of saw palmetto berry they could maximize the herb's effectiveness.
Saw palmetto contains many biologically active chemicals. Unfortunately, we don't know which ones are the most important. We also don't really know how saw palmetto works; it appears to interact with various sex hormones, but it also has many other complex actions that could affect the prostate.
Saw palmetto oil is an accepted medical treatment for benign prostatic hyperplasia (BPH) in New Zealand and in France, Germany, Austria, Italy, Spain, and other European countries.
Typical symptoms of BPH include difficulty starting urination, weak urinary stream, frequent urination, dribbling after urination, and waking up several times at night to urinate. Most, thought not all, research suggests that saw palmetto can markedly improve all these symptoms. Benefits require approximately 4 to 6 weeks of treatment to develop. It appears that about two-thirds of men respond reasonably well.
Furthermore, while the prostate tends to continue to grow when left untreated,1 saw palmetto causes a small but definite shrinkage.2-4 In other words, it isn't just relieving symptoms, but may actually be delaying prostate enlargement. The drug Proscar does this too (and to a greater extent than saw palmetto) but other standard medications for BPH have no effect on prostate size.
Some studies suggest that saw palmetto is equally effective for reducing BPH symptoms as Proscar, and it has one meaningful advantage: It leaves PSA (prostate-specific antigen) levels unchanged. Cancer raises PSA levels, and lab tests that measure PSA are used to screen for prostate cancer. Proscar lowers PSA measurements, and therefore, its use may have the unintended effect of masking prostate cancer. Saw palmetto won't do this. On the other hand, Proscar has been shown to reduce the need for surgery, unlike saw palmetto or any of the other drugs used for BPH.
Saw palmetto may also be equally as effective as another class of standard drugs known as alpha blockers, but may cause fewer side effects.
Note : Before self-treating with saw palmetto, be sure to get a proper medical evaluation to rule out prostate cancer.
Saw palmetto is also widely used to treat chronic prostatitis. An open trial that compared saw palmetto to the drug Proscar for the treatment of chronic nonbacterial prostatitis found that while the drug was effective, the herb was not.5 However, these results do not mean that saw palmetto is ineffective for prostatitis. Because this was an open study, researchers and participants knew who was getting saw palmetto and who was getting the drug. If there was any expectation that the drug would be more powerful than the herb, this in itself would be sufficient to skew the results toward that outcome.
Saw palmetto is sometimes recommended as a treatment for hair loss, but there is no evidence at all that it is effective for this purpose.
The scientific evidence for the effectiveness of saw palmetto in treating prostate enlargement is inconsistent.
At least 10 double-blind studies involving a total of about 900 people have compared the benefits of saw palmetto against placebo over periods of 1 to 12 months.6-13,20,29 In all but three of these studies, the herb improved urinary flow rate and most other measures of prostate disease to a greater extent than placebo. However, in the most recent and perhaps best-designed of these studies, a 1-year trial of 225 men, a saw palmetto failed to prove more effective than placebo.30 Furthermore, a large review of 14 trials with 5,222 men found that saw palmetto did not improve urinary symptom scores or peak urine flow compared to placebo. Subjects taking saw palmetto reported more overall symptom improvement than those taking placebo, but this result is questionable due to inconsistencies among studies.35 Adding to the unsupportived evidence, a more recent well designed, placebo-controlled trial involving 369 men found that saw palmetto even at high doses (three times the standard dose) did not improve urinary flow rate compared to placebo.36
A double-blind study followed 1,098 men who received either saw palmetto or the drug Proscar over a period of 6 months.14 (Unfortunately, there was no placebo group.) The treatments were equally effective, but while Proscar lowered PSA levels and caused a slight worsening of sexual function on average, saw palmetto caused no significant side effects. Both treatments caused the prostate to shrink, but Proscar had a greater effect.
A 52-week, double-blind study of 811 men compared saw palmetto to a standard drug in another class: the alpha-blocker tamsulosin.15 Once again, both treatments proved equally effective. However, saw palmetto caused fewer side effects than the drug. In addition, the herb caused some prostate shrinkage, while the drug caused a slight prostate enlargement.
A study involving 435 men found that the benefits of saw palmetto endure for at least 3 years.16,17 However, there was no control group in this study, making the results unreliable.
A 48-week, double-blind trial of 543 men with early BPH compared combined saw palmetto and nettle root against Proscar and found equal benefits.18 Benefits were also seen with a combination of saw palmetto and nettle root in a 24-week, placebo-controlled study of 257 men.31
Finally, a 6-month, double-blind, placebo-controlled trial of 44 men given a saw palmetto herbal blend (containing, in addition, nettle root and pumpkin seed oil) found shrinkage in prostate tissue.19 No significant improvement in symptoms was seen, but the authors pointed out that the study size was too small to statistically detect such improvements if they did occur.
The standard dosage of saw palmetto for the treatment of BPH is 160 mg twice a day of an extract standardized to contain 85% to 95% fatty acids and sterols. A single daily dose of 320 mg may be just as effective for this condition.21,22 However, taking more than this amount does not, on average, seem to produce better results.23,27 As with many other herbs, the quality of commercial saw palmetto products may vary widely.28 For this reason, it is best to purchase a saw palmetto product that has been evaluated by an independent lab, such as Consumer Labs.
Saw palmetto is thought to be essentially nontoxic.24 In addition, in clinical trials, it has shown little to no adverse effects. For example, in a one-year randomized trial of 225 men, there was no significant difference in adverse events between the groups receiving saw palmetto and placebo.34 And, in a 3-year study, only 34 of the 435 participants complained of side effects, and these were primarily only of the usual nonspecific variety seen with all medications, such as mild gastrointestinal distress.25
There are at least two case reports in which use of saw palmetto was linked to liver inflammation;32-33 however, a subsequent study in rats failed to find that even very high doses of saw palmetto are injurious to the liver. This case report might have been an instance of an allergic or other idiosyncratic reactions; alternatively, something other than saw palmetto may have gotten into the product. One of the above-mentioned cases also involved pancreatitis.33
Finally, there is one report of saw palmetto apparently causing excessive bleeding during surgery.26 The significance of this isolated event isn't clear, but it is probably prudent to avoid saw palmetto prior to and just after surgery, and during the period surrounding labor and delivery. Individuals with bleeding problems (such as hemophilia) should perhaps also avoid saw palmetto, as should those taking any drug that "thins" the blood, such as warfarin (Coumadin), heparin, aspirin, clopidogrel (Plavix), ticlopidine (Ticlid), and pentoxifylline (Trental).
Saw palmetto has no known drug interactions. Safety for pregnant or nursing women, or those with severe kidney or liver disease, has not been established.
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Last reviewed December 2015 by EBSCO CAM Review Board Last Updated: 12/15/2015