An enlarged prostate is almost a certainty in the aging process for men. A man's prostate grows during most of his life but it usually doesn't cause any symptoms or problems until later in life. Benign prostatic hyperplasia (BPH) affects nearly half of men in their 60s and as many as 90% of those in their 70s and 80s.

As the prostate gland enlarges, the layer of surrounding tissue prevents it from expanding, causing a clamp-like effect on the urethra. The bladder may also weaken, resulting in obstructive symptoms such as the partial emptying of the bladder, frequent or interrupted urination, and a diminished urine flow.

Once diagnosed, most men rely on prescription medications, such as 5-alpha-reductase inhibitors (finasteride or dutasteride) or alpha-adrenergic blockers (tamsulosin, alfuzosin, or terazosin), to reduce BPH symptoms. Others, however, will seek alternative, more natural treatments, including saw palmetto.

Treating BPH

Saw palmetto is an extremely slow-growing and long-living dwarf palm tree that is widespread in the southeastern areas of the US. The fruits of saw palmetto are rich in fatty acids and phytosterols. It is the extracts from these fruits that are used to treat BPH. Native Americans have used the fruit to treat a list of problems related to the urinary and reproductive systems. In time, European colonists became aware of its use, and extracts from the fruit became treatment for various conditions including fatigue, recovery from major illness, and urogenital problems.

Proposed theories on how saw palmetto helps with BPH symptoms include anti-inflammatory activity; blocked conversion of testosterone to dihydrotestosterone (DHT), a substance that encourages prostate cell growth; and shrivelling or shrinking of prostate cells.

What do the studies say?

In a 2002 Cochrane Review of past studies comparing saw palmetto to placebo and other medications, research found that 13 studies demonstrated saw palmetto improved patient symptom scores (based on the International Prostate Symptom Scale), individual symptoms, and urine flow measures more than placebo. Also, 2 studies demonstrated saw palmetto had positive effects similar to finasteride on urinary symptom scores and peak urine flow.

While this analysis of previous smaller studies is mostly positive, a large placebo-controlled study was published in the New England Journal of Medicine in 2006 that showed no reduction of symptoms in patients taking saw palmetto as compared to placebo. Critics of this study questioned whether sufficient dosage of active ingredients was given; however, this study was conducted with carefully planned scientific methods and the extract content met criteria set out by alternative medicine experts. More recently, a 2011 study funded by the National Center for Complementary and Integrative Health concluded that saw palmetto did not reduce symptoms associated with BPH when compared to placebo. Currently there is still not enough scientific evidence to support the use of saw palmetto for BPH.

Saw palmetto is considered to be quite safe, when used as directed. Some men may develop mild nausea, reduced libido, or erectile dysfunction when taking saw palmetto, but these side effects are less common than those seen in men taking medications to treat BPH symptoms. Some concern has been expressed that saw palmetto may mask prostate cancer by lowering prostate-specific antigen (PSA) levels. PSA is a protein produced by the prostate that is often found at higher levels in the blood of men who have prostate cancer. Studies have shown that saw palmetto does not affect PSA levels and so should not affect the PSA test used to screen for prostate cancer.

As with any herbal product, saw palmetto will react differently in different people and its use in treating BPH is solely at the discretion of the patient. Also, it is important to note that saw palmetto products used in different studies have varying degree of purity and potency. Currently, Health Canada does not strictly regulate herbs and supplements. It is important to consult a health care provider before starting saw palmetto or any new therapy.


Brennan Robertson, Hon. B.Sc. (Nutrition)

with revisions by the MediResource Clinical team