Saw Palmetto is a plant native to the American Southeast. It has been used traditionally as a treatment for respiratory complaints and conditions of the genitourinary tract. Since the 20th centuries, an extract of the plant has been touted as a treatment for urinary and prostate problems in men.
In 2016, Saw Palmetto was the 15th top-selling herbal supplement in the mainstream US market, with total sales of over $17 million dollars. It was 10th in the US Natural market, with $7.5 million dollars in sales.
What Is Saw Palmetto?
Serenoa repens, commonly known as Saw Palmetto, is the sole species currently classified in the genus Serenoa and is in the Arecaceae (Palm) family. It is a small, low-growing, dwarf-palm tree native to Southeastern North America, particularly Florida.
The leaves have a sharp, spiny edge that can cut the clothing or legs of those who encounter it (and from whence its name is derived). The Saw Palmetto plant produces berries, which when ripe (in the fall) are a bright orange to purple to almost black in color. They are egg-shaped, and about 3 cm long.
Saw Palmetto is used in several forms of traditional herbal medicine. Native Americans used the fruit for food and to treat a variety of urinary and reproductive system problems. The Mayans drank it as a tonic, and the Seminoles used the berries as an expectorant and antiseptic.
Saw palmetto fibers have been found among materials from indigenous people as far north as Wisconsin and New York, strongly suggesting this material was widely traded prior to European contact.
In the early 1900s, men used the berries to treat urinary tract problems, and even to increase sperm production and boost libido.
Researchers have determined that an extract made from dried Saw Palmetto berries contains the potentially medicinally active components. This extract is known as the liposterolic extract (LESP) and is the subject of many in vitro and in vivo animal and human clinical studies.
The composition of the extract is 85% fatty acids and 0.3-0.4% sterols (unsaturated steroid alcohols). The free fatty acids include lauric, myristic, palmitic, and oleic acids. The predominant sterol in LESP is beta-sitosterol.
Saw Palmetto is available as tablets, capsules or as a liquid extract.
Saw Palmetto is classified as a dietary supplement in the United States and falls under FDA regulations pursuant to the Dietary Supplement Health and Education Act (DSHEA). This law restricts claims that Saw Palmetto can be used to treat, cure, or prevent any disease or condition, because only a drug, not a dietary supplement, can legally make such claims
Can You Get Saw Palmetto from Food?
Raw or cooked Saw Palmetto berries can be eaten but the taste is described as soapy, strong and unpleasant. Modern studies of Saw Palmetto are usually based on a chemical extract made from the berries. The potentially bio-active components of Saw Palmetto are unique to it.
Is There Any Research?
As of February 2018, the biomedical literature (PubMed.gov) I found 540 articles about Saw Palmetto or Serenoa repens dating back to 1954. Most of these research studies involve experiments with laboratory animals (mostly rats or mice) or “test tubes” (in vitro studies). Of these 540 articles, 18% (97 studies) involve human subjects.
The U.S. government’s database of clinical research trials (ClinicalTrials.gov) describe 9 completed clinical trials which studied the effects of saw palmetto on medical conditions including prostate cancer, thinning hair in women, lower urinary tract symptoms (LUTS) and benign prostatic hyperplasia (BPH – see below).
By comparison, I searched for articles in PubMed for finasteride (Proscar®), an FDA-approved drug for the treatment of BPH. There were 2907 studies cited in PubMed about finasteride with 407 involving human subjects and 46 clinical studies on ClinicalTrials.gov.
Although there are a fair number of scientific studies involving saw palmetto, most involve animal or in vitro studies. A positive effect under these conditions does not necessarily translate into an equivalent response in humans.
Most of the studies that involve human subjects are plagued either by lack of control groups, faulty design, the use of a mixture of ingredients in the test supplement, or conflicting results. More well planned human trials are necessary.
Does Saw Palmetto Help the Prostate?
The normal anatomy, development and physiology of the prostate gland is beyond the scope of this article, but that information can be found here.
Non-cancerous (benign) enlargement (hyperplasia) of the prostate, abbreviated as BPH, often occurs as men age, and affects about 50 percent of men between the ages of fifty-one and sixty and up to 90 percent of men older than eighty.
As the prostate enlarges, the gland presses against the urethra and pinches it. The bladder wall becomes thicker. Eventually, the bladder may weaken and lose its ability to empty completely, leaving some urine in the bladder. The narrowing of the urethra and urinary retention— the inability to empty the bladder completely—cause many of the problems associated with BPH. Lower urinary tract symptoms (LUTS) suggestive of BPH may include:
- urinary frequency—urination eight or more times a day
- urinary urgency—the inability to delay urination
- trouble starting a urine stream
- a weak or an interrupted urine stream
- dribbling at the end of urination
- nocturia—frequent urination during periods of sleep
- urinary retention
- urinary incontinence—the accidental loss of urine
The cause of BPH is not well understood. Throughout their lives, men produce testosterone, a male hormone, and small amounts of estrogen, a female hormone. As men age, the amount of active testosterone in their blood decreases, which leaves a higher proportion of estrogen.
Scientific studies have suggested that benign prostatic hyperplasia may occur because the higher proportion of estrogen within the prostate increases the activity of substances that promote prostate cell growth.
Another theory focuses on dihydrotestosterone (DHT), a male hormone that plays a role in prostate development and growth. Some research has indicated that even with a drop in blood testosterone levels, older men continue to produce and accumulate high levels of DHT in the prostate. This accumulation of DHT may encourage prostate cells to continue to grow.
In men, testosterone is converted into DHT by an enzyme called 5-alpha reductase (5-AR). The liposterolic extract of saw palmetto (LESP) was found to inhibit 5-AR in a variety of in vitro and animal systems. Human trials of LESP in the treatment of BPH has had mixed results:
- A 2012 Cochrane review of 32 randomized controlled trials involving 5,666 men with BPH found that Serenoa repens, at two and three times the usual dose, provides no improvement in urinary flow measures or prostate size in men with lower urinary tract symptoms consistent with BPH.
- A 2011 double-blind, placebo-controlled, randomized trial in 369 older men demonstrated that Saw Palmetto extract administered at up to three times the standard daily dose (320 mg) did not reduce the urinary symptoms associated with BPH more than placebo. In addition, a 2009 Cochrane review of nine trials concluded that Saw Palmetto has not been shown to be more effective than placebo for this use.
- A 2014 randomized trial of 225 men with lower urinary tract symptoms (LUTS) and BPH examined the efficacy and tolerability of combination therapy between Saw Palmetto, lycopene, and selenium plus tamsulosin (Flomax) versus single therapies. The findings suggest that a combination therapy of saw palmetto, lycopene, selenium, and tamsulosin is more effective than single therapies in improving International Prostate Symptom Score (IPSS) and increasing maximum urinary flow rate. It was noted that after 6 months of treatment, the combination therapy significantly improved symptom scores compared with single therapy, and from 6 to 12 months, combination therapy demonstrated significant improvement in urine flow rate compared to tamsulosin alone. There were no reported treatment-related adverse events associated with combination therapy.
- A 2017 study of looked at 186 men treated with either Silodosin alone (an FDA approved alpha blocker which relaxes muscles in the prostate and bladder) or in combination with an extract of Serenoa repens (Ser) for a period of at least 1 year. After the trial period, both groups had significant improvement in their IPSS, however those on combination therapy had a statistically greater improvement than those taking Silodosin alone. Results were similar when researchers compared the two groups for clinically meaningful improvements in lower urinary tract symptoms. 
Saw Palmetto has been approved for use in Europe by the European Medicines Agency for treatment of symptoms associated with BPH under the “traditional usage guidelines”. (To see what this means, check out my story on horehound.)
The German Commission E approved the internal use of saw palmetto berry “for urination problems in benign prostatic hyperplasia stages I and II. Traditional uses include chronic or subacute cystitis, catarrh of the genito-urinary tract, testicular atrophy, sex hormone disorders, and, specifically, prostatic enlargement in modern phytotherapy.”
Although several small studies have suggested modest benefit of Saw Palmetto for treating symptoms of BPH, larger studies found that Saw Palmetto was no more effective than placebo for treatment of urinary symptoms related to BPH.
Does It Saw Palmetto Help Hair Loss?
Male pattern baldness (MPB) is the common type of hair loss that develops in most men at some stage, affecting up to 50% of males between 18 and 40 years old. It primarily affects the top and front of the scalp. The condition is sometimes called androgenetic alopecia. Male pattern hair loss is believed to be due to a combination of genetics and the male hormone dihydrotestosterone.
Men with androgenic alopecia typically have higher 5-alpha-reductase, lower total testosterone, higher unbound/free testosterone, and higher free androgens, including DHT.
Over time, DHT causes hair follicles to become smaller. As they get smaller, the hair that grows back tends to be finer, thinner, and shorter. Eventually, it takes longer for hair to grow back. Eventually, the follicles will shrink so that no hair grows at all.
Given that LESP has been shown to inhibit 5-AR (which converts testosterone to DHT), it is reasonable to postulate that LESP may have value in the treatment of MPB.
In a study by Wessagowit et al, 50 male volunteers, aged 20-50 years, received topical S. repens products for 24 weeks. The average hair count and terminal hair count were increased at 24 weeks compared to baseline. However, the effects did not persist after the products were stopped.
A 2012 study by Rossi et al compared Saw Palmetto with finasteride (Proscar®) in the treatment of androgenetic alopecia. One hundred men were divided into two groups, one of which received saw palmetto (320 mg/day) and the other finasteride (1 mg/day) for a period of 2 years.
The results showed that only 38% of patients treated with Serenoa repens had an increase in hair growth, while 68% of those treated with finasteride noted an improvement. Moreover, finasteride was more effective for more than half of the patients (33 of 50, i.e. 66%), with level II and III alopecia.
Murugusundram’s review  of the literature and the proceedings of hair research societies concluded that there is insufficient evidence supporting the use of saw palmetto in male pattern baldness.
There is insufficient evidence to support the use of saw palmetto in the treatment of male pattern baldness.
Does It Help Testosterone Levels?
I found three studies that look at whether Saw Palmetto can raise testosterone levels. The first, in 1988, by Casarosa, Di Coscio and Fratta, looked at 20 men, aged 50-70, who suffered from BPH. They received 320 mg of LESP for 30 days.
They had plasma levels of testosterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) determined before and after the 30 days. No change in the plasma hormone levels were found.
A 2008 study by Angwafor and Anderson divided 42 healthy men (ages-37-70) into two groups. One group received 800 mg/day of Mytosterone™ and the other group 2000 mg/day. Mytosterone™ is an over-the-counter supplement touted to boost testosterone levels. Its ingredients are listed as:
- Saw Palmetto
- Serenoa Repens (This is just another name for Saw Palmetto - what’s up with that??)
- Heamatococcus pluvialis: a freshwater species of Chlorophyta from the family Haematococcaceae which has a high content of the strong antioxidant astaxanthin.
Serum total testosterone, serum DHT and estradiol were tested on days 0, 3, 7, and 14 of treatment. The researchers found that either dosage cause a significant increase in testosterone and decrease in DHT within 3 days of starting the supplement. There was no significant difference between the response at the higher than the lower dosage. Estradiol was also decreased but declined more with the higher dose of Mytosterone™.
In 2014, Anderson  published a single-blind study of 20 healthy men (ages 21-70) using the same supplement (now labeled as Resettin®). He has three groups- one receiving 800mg/day, the second 1200mg/day, and the third receiving lecithin as a placebo. After 2 weeks on the supplement or placebo, the men underwent a 2-week “washout period” followed by a crossover to either the supplement or placebo group.
Anderson found no statistically significant differences on serum testosterone levels between the treatment and placebo groups.
No convincing evidence exists that Sal Palmetto increases testosterone levels in men. Published studies have used only small groups of subjects and are confounded by the fact that mixtures of Saw Palmetto with other substances were used, making it impossible to attribute any effects to Saw Palmetto alone.
Does it “Support the Urological System”?
The urological system consists of the kidneys, ureters, bladder and urethra (part of which is surrounded by the prostate gland in men). I’ve already discussed (see above) the effect of Saw Palmetto on lower urinary tract symptoms (LUTS) and BPH. I could find no evidence of any effect of Saw Palmetto on the kidney or kidney stones.
Studies in show that Saw Palmetto can alter “urodynamic parameters” in the bladders of laboratory rats but there is no justification for extrapolating these results to humans.
There is no evidence that Saw Palmetto can “support” (affect the healthy functioning) of the urological system.
Is Saw Palmetto (and or Supplementation) Safe?
Saw Palmetto is well-tolerated in most patients. The most frequent side effects are minor gastrointestinal problems, such as nausea, which can be decreased by taking it with food.
A 2009 systematic review of Serenoa repens by Agbabiaka et. al assessed all available human safety data to that point. Forty studies were included: 14 placebo-controlled randomized clinical trials (RCTs, n=1,557); 12 comparative RCTs (n=3,125); four non-randomized clinical trials (n=179); six uncontrolled trials (n=1,034); and four case reports or series (n=5).
Data from National Reporting Schemes based in UK, Germany, Australia, USA and at WHO, manufacturers and one herbalist organization were included.
Adverse events reported in placebo-controlled RCTs (14 RCTs, n=1,557) included diarrhea and other gastrointestinal problems (n=18), headache (n=6), fatigue (n=6), common cold (n=3), gastrointestinal bleeding (n=3), urinary problems (n=2), nausea (n=1) and vomiting and vertigo (n=1).
Adverse events reported in non-placebo-controlled RCTs (12 RCTs, n=3,125) included gastralgia, abdominal discomfort, hypertension, decreased libido, impotence, ejaculation disorder, gastrointestinal disorder, rhinitis, headache, fatigue, dizziness, and skin disorders.
Saw Palmetto is not recommended for use during pregnancy or lactation.
Available data suggested that S. repens was well tolerated by most users and was not associated with serious adverse events. Most adverse events are mild, infrequent, and easily reversible.
Saw Palmetto (Serenoa repens) is frequently used for the relief of symptoms associated with BPH. Although the scientific evidence, to date, does not support its use for BPH, it is well tolerated and has little serious side effects associated with it.
Likewise, there is little research to support saw palmetto to boost testosterone levels or treat male pattern baldness.
Until there are better designed, double-blind studies that show significant positive effects of Saw Palmetto or its components, I think Saw Palmetto is best avoided - just like the sharp, spiny edges of its leaves.