Saw Palmetto

Extracts from the fruit of the Saw palmetto tree are among the most popular supplements used by men to help support the prostate gland. The Saw palmetto is an attractive, small palm native to the West Indies and the Atlantic coast of North America. It grows from six to 10 feet high and forms multiple fans of spiny-toothed leaves that are two feet or more in length. Its berries are a traditional herbal medicine used to treat lower urinary tract symptoms in men and it is popularly known as the male plant catheter or the prostrate palm (no pun intended) due to its low-growing habit.

Botanically, the Saw palmetto has two names: Sabal serrulata and Serenoa repens. It’s sometimes also referred to as Serenoa serrulata or Sabalis serrulatae which, not surprisingly, can lead to confusion. In some cases, men have taken both a Sabal supplement and one containing Serenoa. Although this is unlikely to be harmful, it is unnecessarily expensive.

Saw Palmetto Honey 

The Saw palmetto’s ivory flowers have a powerful scent that attract over 300 species of insect, including honeybees who collect the pollen and nectar. If you ever see Saw palmetto honey for sale, grab it as it has both a delightfully flavour and medicinal qualities.

Each dwarf palm bears from one to five densely branched sprays of flowers up to two feet long, each of which sets several thousand dark berries. These have a nutty, vanilla flavour that is a favourite among many species of wildlife, including black bears, white-tailed deer, raccoons, wild turkeys, fox and even tortoises.

Biologically Active Fruits

Serenoa_repensSaw palmetto berries are a rich source of fat-soluble sterols (such as ß-sitosterol, campesterol and stigmasterol) plus antioxidant polyphenols, including flavonoids. These are used as a traditional herbal medicine to improve symptoms caused by a benign enlargement of the prostate gland (BPH).

BPH causes two types of male lower urinary tract symptoms: obstructive or voiding symptoms and irritative or filling symptoms.

The obstructive symptoms include:
• Hesitancy (difficulty starting to urinate)
• Straining (having to force urine out)
• A weak urinary stream
• Stopping and starting mid-flow
• Dribbling of urine after voiding
• Urinary retention (inability to completely empty the bladder)

The irritative symptoms include:
• Urgency (a sudden need to go to the toilet)
• Frequency
• Nocturia (waking to pass urine at night)
• Urinary discomfort
• Urinary incontinence
• A feeling of not having emptied the bladder fully.

Saw palmetto berry extracts are most effective against irritative prostate symptoms, which are often more troublesome than the obstructive symptoms.

The exact way in which Saw palmetto berry extracts work is unknown although there are several theories.  While Saw palmetto does not alter the level of circulating testosterone hormone,  it does appear to affect testosterone metabolism in prostate cells.

Does It Block 5-Alpha-Reductase?

Enlargement of the prostate gland due to benign prostatic hyperplasia (BPH) is dependent upon the conversion of testosterone to another more powerful hormone, dihydrotestosterone (DHT). This reaction is catalysed by an enzyme, 5-alpha-reductase, which is targeted by drugs such as finasteride and dutasteride, prescribed to treat BPH. The inhibition of testosterone metabolism reduces prostate size to improve urinary flow rate and obstructive symptoms.

In prostate cell cultures, Saw palmetto extracts have also been shown to block the activity of 5α-reductase by up to 45%. Significant reductions in DHT production, and a resulting increase in cell testosterone concentrations, were also found in prostate biopsy samples from men who’d taken Serenoa repens extracts for 3 months. These changes were most noticeable in biopsies taken from the middle lobe of the prostate. Selective shrinking of the central portion of the prostate, which directly surrounds the urethra, might explain why studies do not show appreciable shrinking of the whole gland in men taking Saw palmetto, despite significant improvements in urinary outflow and obstructive symptoms.

Interestingly, two different types of 5α-reductase enzyme are present in the human prostate: isoenzymes type 1 and 2, with the type 2 enzyme predominating. The prescription drug, finasteride, mainly inhibits 5α-reductase-2, while Saw palmetto fruit extracts inhibit both. Pharmaceutical drugs are currently in development to inhibit both isoenzymes as this appears to result in a greater, more consistent suppression of DHT than selective inhibitors.

Other researchers believe it’s more likely that Saw palmetto extracts compete with DHT for their receptors, however, so that cells detect less DHT even if levels are not greatly reduced.

The controversy about whether or not Saw palmetto extracts interferes with the action of 5-alpha-reductase enzymes continues, but a mounting body of evidence suggests that it at least part of its effectiveness is due to this action.

Is It An Oestrogen Blocker?

In one study, 35 men with BPH who were due to have prostate surgery were randomised to receive either Saw palmetto berry extracts (160mg three times a day) or inactive placebo in the three months leading up to their op. The number and type of hormone receptors in their prostate cells was then analysed. In the 17 men who received placebo, oestrogen receptors were found in the nucleus of the prostate cells in 14, and in the main body of the prostate cells in 12. In the men who took Saw palmetto extracts, oestrogen receptors were only detected in the prostate cell nucleus of one out of 18 men, and in the main body of the prostate cells in six men. A significant reduction in progesterone hormone receptors was also noted. This suggests that Saw palmetto may have a significant anti-oestrogen effect within the prostate gland which is suggested to reduce swelling.

One of the most recent cell studies has identified two new prostate proteins with which the beta-sitosterol present in Saw palmetto can interact. One of these (17b-HSD4) is an important ‘housekeeping enzyme’ that inactivates the most powerful oestrogen (17b-estradiol) found in the body. Less is known about the other protein (E-Syt1), but it may be involved in cell proliferation and has been linked to invasiveness in some types of cancer.

Is It An Alpha-Blocker?

Some of the most effective prescription drugs prescribed to treat BPH symptoms interact with alpha-adrenergic nerve receptors and are known as alpha-blockers. These trigger relaxation of smooth muscle cells which, in the prostate, reduces spasm and widens the urinary outlet to improve both obstructive and irritative symptoms. Saw palmetto also appears to have alpha-blocker activity which is only slightly lower than that of prescribed alpha-blocker drugs such as tamsulosin, although so far this action has not been fully investigated.

Other Possible Actions

Saw palmetto appears to affect the movement of calcium ions in and out of the cells to reduce smooth muscle cell contraction. Some of its effects may therefore related to relaxation of smooth muscle cells in the bladder neck and prostate gland. Saw palmetto also has an anti-inflammatory action similar to that of aspirin and ibuprofen, by inhibiting cyclo-oxygenase enzymes which may reduce prostate swelling.

However it works, saw palmetto is able to reduce the over-proliferation of prostate cells that is associated with BPH to improve symptoms – and this interference with growth of prostate cells even occurs when cells have been stimulated to grow by a powerful growth factor.

How Effective Is Saw Palmetto For BPH?

saw palmetto supplementsMore than 20 early, randomised, double-blind, placebo-controlled trials showed that standardised extracts of Saw palmetto berries (providing 85% to 90% fatty acids and sterols) relieved the symptoms of BPH, especially night-time urinary frequency (nocturia) which was reduced by 33% to 74% (versus 13% to 39% with placebo).

A few studies even found Saw palmetto held its end up when compared with prescription drugs. One trial,  involving over 1000 men with moderate symptoms of BPH, found Saw palmetto was as effective as the prescription-only drug, finasteride, with both treatments achieving a 38% decrease in BPH symptoms over a 6 month period. Sexual function in the men using Saw palmetto did not change, although it deteriorated significantly in those taking the finasteride.

Another study compared Saw palmetto against the prescribed alpha-blocker drug, prazosin, in 45 men. At the end of the 12 week trial, flow rate and symptoms improved in both groups to a similar extent, although improvements in irritative symptoms were slightly less with Saw palmetto.

In a recent study, 103 men referred to a Korean hospital with bothersome BPH symptoms all received the alpha-blocker drug, tamsulosin, but half also received additional treatment with Serenoa repens at a dose of 320mg per day. At 6 months, and at 12 months, total prostate symptoms score showed a significantly greater improvement in the men taking both treatments than in those on the prescribed drug alone. Side effects were slightly higher in those taking the combination however (20% versus 16.9% with tamsulosin alone).

Another study randomised 225 men with BPH to receive either tamsulosin or a combination therapy based on Serenoa repens (plus lycopene and selenium) or both. Symptom improvement was significantly greater for the combination therapy than for either treatments alone at six months, with improvements persisting at 12 months, with better quality of life, too.

Some studies found little benefit from Saw palmetto therapy, however, although a few of these trials only lasted four weeks which is too short a time to show an effect – other trials have found that it usually takes around six weeks for benefits to become noticeable. A Cochrane systematic review of 32 randomized, controlled trials (which included those only lasting four weeks) concluded that Serenoa repens, at double and triple doses, did not improve urinary flow measures or prostate size in men with lower urinary tract symptoms consistent with BPH.

Whether or not to try it is a personal decision to make together with your doctor. If you are being managed by ‘watchful waiting’ and are not on any conflicting medications, it remains an option and may help to postpone the need for prescription medicines.


In prostate cells cultures, Saw palmetto extracts were found to suppress the activity of genes associated with inflammation. In a study involving 56 men with chronic bacterial prostatitis, all of whom received an antibiotic (prulifloxacin) for 15 days, one group of 28 patients also took Serenoa repens for 8 weeks. The eradication of infection was the same in all men, but those who also received saw palmetto had significantly reduced pain and improved urinary symptoms.

Prostate Cancer

There is currently insufficient evidence to support the use of Saw palmetto in combination with medical treatments.


Usually 160mg, twice a day, but follow manufacturer’s instructions.

Only Saw palmetto fruit/berry extracts are active against BPH, so avoid those that do not specify which part of the tree they contain. Cheaper supplements may contain leaf extracts, or may only provide non-therapeutic amounts of the active ingredients.

In the UK, it is important to choose a supplement that is licensed under the Traditional Herbal Registration (THR) scheme which will contain a standardised, pharmaceutical grade of Saw palmetto fruit extracts.

NB Only take Saw palmetto if your doctor has confirmed that you have BPH. If you are taking any prescribed medicines, seek advice from your doctor before taking it, especially before combining it with other prostate medicines, as this should only be done under medical supervision.

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