Herbal remedies are becoming increasingly popular to treat many different diseases and conditions that are normally treated with drugs. Saw palmetto is a very popular herbal supplement often used to treat symptoms of benign prostatic hyperplasia (BPH). Read on to see what the science says about saw palmetto.
What Is Saw Palmetto?
Saw palmetto is an extract of the berry of the saw palmetto tree (Serenoa repens) that is native to Southeast North America .
Saw palmetto has been used for centuries in Asia and North America for the treatment of benign prostatic hyperplasia (BPH) . Benign prostatic hyperplasia is a noncancerous enlargement of the prostate.
The Seminole tribe in Florida used the herb to treat urinary and sexual problems .
The plant gained recognition in the United States when it was listed as an official remedy in the US Pharmacopoeia in 1906. Since the 1990s it has been one of the top 10 most sold herbs in the U.S, with more than 2 million men using the herb regularly [3, 4].
In Europe, saw palmetto is the most popular herbal supplement used to treat BPH. Global sales of the herb total more than $700 million annually .
Saw Palmetto’s Mechanisms Of Action
- Saw palmetto inhibits 5-reductase, an enzyme that converts testosterone into dihydrotestosterone (DHT) .
- Saw palmetto blocks 1-adrenoceptors [6, 7].
- Saw palmetto reduces the activity of several inflammation-related genes .
- Saw palmetto increases the production of p57 protein, a protein which decreases tumors [9, 10].
- Saw palmetto decreases the production of p21 proteins, which advance tumor growth [9, 11].
Benefits Of Saw Palmetto
1) May Treat Benign Prostatic Hyperplasia
Benign prostatic hyperplasia (BPH) is a growth of the prostate that is not due to cancer. It is very common in older men . Nearly 40% of American men over the age of 60 and 90% of men over 80 have BPH .
However, a study in 100 men aged 45 and older found no difference in treating BPH after 72 weeks of saw palmetto (DB-RCT) .
Finasteride (Propecia) is a prescription 5-reductase inhibitor that is commonly used to treat BPH. A year-long study found that saw palmetto was more effective than finasteride in treating excessive nighttime urination. It was less effective in treating other symptoms related to BPH .
A study of 2,008 men found that 72 weeks of saw palmetto was no more effective than a placebo in the treatment of BPH .
A 2002 Cochrane review concluded that saw palmetto was effective in treating BPH. However, a 2009 Cochrane review that included larger and longer trials found that saw palmetto had no effect on BPH [18, 19].
A 2016 review only included trials with a special standardized extract of saw palmetto called Permixon. Permixon was effective in improving urinary symptoms of BPH compared to placebo. It was just as effective as finasteride in treating BPH .
This suggests that the lack of an effect found in the most recent Cochrane review was due to the differences in the saw palmetto extracts used.
2) May Improve Urinary Tract Symptoms
Saw palmetto may treat lower urinary tract symptoms (LUTS). LUTS is a range of symptoms that include :
- Painful urination
- Increased frequency of urination
- Incomplete bladder emptying
- Weak stream
- Excessive nighttime urination
A study in 225 patients showed that 12 months supplementation with saw palmetto along with lycopene, selenium, and tamsulosin was effective in the treatment of LUTS . Tamsulosin is a drug commonly used to treat symptoms of BPH.
A study (DB-RCT) in 85 men with LUTS found that saw palmetto given over 24 weeks was more effective in improving symptoms than placebo .
Another study (DB-RCT) in 369 men with LUTS aged 45 years and older found that saw palmetto extract given over 72 weeks was no more effective than placebo .
Saw palmetto extract significantly decreased the number of nighttime urinations compared to a placebo and two other drugs used to treat excessive nighttime urination (DB-RCT) in men with LUTS .
3) Increases Hair Growth in Male-Pattern Baldness
Saw palmetto is commonly used to treat hair loss caused by male-pattern baldness (androgenic alopecia). Male-pattern baldness is the loss of hair in men due to genetics and too much dihydrotestosterone .
A study with 50 men with male-pattern baldness found that saw palmetto taken daily for two years increased hair growth on the top (crown) of the head .
A case report found that a 24-year-old woman with pattern hair loss responded to treatment with saw palmetto .
One study found that topical saw palmetto products were able to increase hair growth in 50 men with male-pattern baldness .
4) May Reduce the Risk of Prostate Cancer
Another study found that blocking 5-reductase saw palmetto extract is able to decrease the growth of prostate cancer cells .
However, a long-term study found no association between the consumption of saw palmetto and the risk of developing prostate cancer .
5) May Improve Sexual Function
Saw palmetto has traditionally been used to treat erectile dysfunction and improve sexual function .
A pilot trial showed a significant increase in sexual function in 82 men aged 30 and older .
Note: This study was funded by the manufacturer of the brand of saw palmetto used (Prostasan).
Another study found no significant difference between saw palmetto and a placebo in treating sexual dysfunctions .
6) May Increase Testosterone Levels
By decreasing the conversion of testosterone to DHT, saw palmetto can increase testosterone levels.
One study saw a significant increase in testosterone after three months of 320 mg saw palmetto .
An unblinded study (RCT) in 32 men found that 80 mg saw palmetto extract twice a day for six days increased testosterone levels compared to placebo .
7) Improves Quality of Life
Quality of life is a measure of physical, social, and emotional well-being.
Supplementation with 320 mg saw palmetto daily for 8 weeks significantly increased quality of life scores by 42% in a pilot trial in 82 men .
Side Effects and Precautions
A systematic review assessed human safety data of saw palmetto and found that side effects are mild and similar to those with placebo .
According to the review, the most frequently reported side effects are: 
More serious adverse events like death and brain hemorrhage were reported in isolated incidents, but their link with saw palmetto is highly questionable .
There have been two cases of pancreatic inflammation in individuals using saw palmetto .
In one patient, saw palmetto caused liver inflammation .
In another case report, acute liver damage was reported with the use of saw palmetto .
Drugs That Reduce Clotting
One patient taking saw palmetto extract experienced significantly more blood loss than normal during surgery and reduced clotting of their blood (bleeding time). The patient’s clotting ability returned to normal after stopping treatment with the extract .
Because of this, saw palmetto should not be taken by drugs that reduce clotting. These include:
- Warfarin (Coumadin)
- Apixaban (Eliquis)
- Rivaroxaban (Xarelto)
- Clopidogrel (Plavix)
- Ibuprofen and other NSAIDs
Saw Palmetto may reduce the effectiveness of birth control pills by lowering estrogen levels 
Because saw palmetto inhibits DHT conversion it should not be used with prescription DHT blockers like finasteride (Propecia).
Saw Palmetto In Combination With Other Treatments
1) Nettle Root
The combination of extracts from saw palmetto fruit and nettle root was similar to finasteride in improving urinary symptoms in patients with BPH .
Astaxanthin combined with saw palmetto extract was more effective in stopping the growth of cancer cells than saw palmetto extract alone .
3) Pumpkin Seed Oil
A study found that a combination of saw palmetto and pumpkin seed oil greatly improved symptoms of BPH and quality of life, and decreased prostate specific antigen (PSA) levels .
Individual Experiences With Saw Palmetto
One user noted a dramatic decrease in hair loss after using saw palmetto.
Another user found it was much easier to pass urine. They stated that “before it stopped, start, stop, start, and now there is a steady flow of urine every time I go. However, I am still getting up 2 or 3 times during the night to pass urine”.
One user took saw palmetto for 16 years and it helped improve stream size and decreased urgency to urinate.
Some people have experienced negative effects from the herb. After using it for a few months, one user got very sick, “like hitting strong flu”.
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