Saw palmetto is an extract of the berries of Serenoa repens, a small palm native to the southeastern United States, and it is one of the most popular ingredients in men's prostate health supplements. It is well tolerated, but the most rigorous human research, including two large NIH-funded trials and a 2023 Cochrane review, found that saw palmetto alone did not improve urinary symptom scores more than a placebo.
Key Takeaways
- Saw palmetto supplements are usually a fat-soluble (liposterolic) extract of the berry, standardized to about 85-95% fatty acids, studied at 320 mg a day.
- In lab studies the extract inhibits 5-alpha-reductase, enzymes involved in male hormone metabolism, but how that translates to people is unproven.
- The NIH-funded STEP and CAMUS trials and a 2023 Cochrane review of 27 trials found little to no difference from placebo in urinary symptom scores or quality of life.
- It is generally well tolerated; mild stomach upset and headache are the most common complaints. Talk to your doctor or pharmacist if you take a blood thinner or a hormone-related medicine.
- Pumpkin seed has one large one-year trial with mixed results; green tea has no solid human data for urinary comfort.
- New or changing urinary symptoms deserve a check with a clinician, including a conversation about PSA testing, rather than relying on a supplement.
Evidence grade: Strong. High-certainty evidence from a Cochrane review of 27 randomized trials (4,656 men), including two NIH-funded trials, consistently shows saw palmetto alone provides little to no improvement in urinary symptom scores compared with placebo.
What Is Saw Palmetto?
Saw palmetto is a small palm that grows 6 to 10 feet tall and is native to the West Indies and the southeast coast of North America [1]. Its berries are the part used in supplements. The plant's botanical name is Serenoa repens; older literature also calls it Sabal serrulata [4].
Supplements rarely contain the whole dried berry. Most products, and nearly all clinical trials, use an oily extract made by pulling the fat-soluble compounds out of the berry with a solvent. These extracts are mostly fatty acids (free or bound in esters), with smaller amounts of plant sterols. The European Medicines Agency (EMA) monograph describes a hexane extract containing 92% fatty acids [5], and the extract used in the NIH-funded CAMUS trial was standardized to 85-95% fatty acids as marker substances [3].
Because extraction methods differ, products are not interchangeable. A laboratory comparison of seven commercial saw palmetto extracts found that all of them inhibited the target enzymes, but their potency varied widely between brands and even between two batches of the same brand [6].
Saw Palmetto Forms Compared
| Form | How it is made | Where it appears in research | What to know |
|---|---|---|---|
| Hexane extract | Fat-soluble compounds extracted with hexane; EMA describes 92% fatty acids | EMA "well-established use" monograph at 320 mg a day [5] | The 2023 Cochrane review found no difference in results between hexane extracts and other extracts [1] |
| Ethanol extract | Extracted with 90-96% ethanol | CAMUS trial, standardized to 85-95% fatty acids [3]; EMA "traditional use" monograph [5] | CAMUS tested up to three times the usual dose with no advantage over placebo [3] |
| Supercritical CO2 extract | Extracted with pressurized carbon dioxide | STEP trial, 160 mg twice daily [2][3] | No difference from placebo over one year [2] |
| Ground berry powder | Dried, powdered whole berry | Not the form used in the major trials | A label that lists only "berry" or "powder" does not tell you the fatty acid content |
How Saw Palmetto Is Thought to Work
The idea behind saw palmetto is mostly mechanistic. In cell studies, liposterolic saw palmetto extract inhibits both type 1 and type 2 forms of 5-alpha-reductase, enzymes involved in androgen (male hormone) metabolism [6][7]. Researchers have also proposed anti-inflammatory and anti-proliferative actions in cells [3].
The gap is between the lab dish and the person. A 2001 review noted that no clinical studies had shown a decrease in blood dihydrotestosterone (DHT), a potent androgen, or in prostate-specific antigen (PSA) with saw palmetto [7]. The CAMUS investigators wrote that none of the proposed mechanisms had been conclusively proven [3], and the EMA monograph states plainly that the mechanism of action is not known [5].
What Human Research Found
Most of these trials enrolled men over 50 with moderate urinary symptoms attributed to an enlarged prostate (benign prostatic hyperplasia, or BPH), and measured symptom questionnaires such as the American Urological Association Symptom Index (AUASI) or the International Prostate Symptom Score (IPSS).
The STEP trial (2006)
The Saw palmetto Treatment for Enlarged Prostates (STEP) study randomly assigned 225 men over 49 with moderate-to-severe symptoms to saw palmetto extract (160 mg twice a day) or placebo for one year [2]. There was no significant difference between the groups in symptom scores (mean difference 0.04 points), maximal urinary flow rate, prostate size, urine left in the bladder after voiding, quality of life, or PSA levels. Side effects were similar in both groups [2].
The CAMUS trial (2011)
Some people argued that STEP used too low a dose or the wrong extract. The NIH-funded CAMUS trial tested both ideas: 369 men aged 45 and older at 11 North American sites took an ethanol extract at 320 mg a day, increased to 640 mg and then 960 mg a day, or a matching placebo, for 72 weeks [3]. Symptom scores fell by 2.20 points with saw palmetto and by 2.99 points with placebo, a difference that slightly favored placebo. Saw palmetto was no better than placebo on any secondary outcome, including nighttime urination, urinary flow, sexual function and sleep quality, and no side effects were clearly attributable to it [3].
The 2023 Cochrane review
Cochrane reviews pool every qualifying randomized trial and grade how certain the evidence is. The 2023 update included 27 studies with 4,656 participants, 19 of which compared saw palmetto alone with placebo [4]. Limiting the analysis to studies at low risk of bias, saw palmetto resulted in little to no difference in urinary symptom scores at 3-6 months (high-certainty evidence) or at 12-17 months (high-certainty evidence), and little to no difference in quality of life. Adverse events were about the same as placebo (moderate certainty). For combinations of saw palmetto with other herbs, the review found the evidence uncertain (low certainty) [4]. Ten of the included studies were funded by industry [4].
Other uses
Saw palmetto is also promoted for male-pattern hair loss, sometimes applied to the scalp. NCCIH notes that only a few small studies exist and the evidence is too limited to draw conclusions [1].
Evidence summary
| Outcome | What trials found | Certainty |
|---|---|---|
| Urinary symptom scores (short term, 3-6 months) | Little to no difference vs placebo [4] | High |
| Urinary symptom scores (long term, 12-17 months) | Little to no difference vs placebo [4]; no benefit at up to 960 mg a day over 72 weeks [3] | High |
| Quality of life score | Little to no difference vs placebo [4] | High |
| Urine flow, prostate size, PSA | No significant difference vs placebo over one year [2] | Moderate (single large trial, consistent with [3]) |
| Adverse events | About the same as placebo [4] | Moderate |
| Saw palmetto combined with other herbs | May make little to no difference; uncertain [4] | Low |
| Hair | Too few small studies to conclude [1] | Very limited |
Doses Used in Studies
| Source | Form | Daily amount | Duration |
|---|---|---|---|
| EMA monograph [5] | Hexane extract (92% fatty acids) | 320 mg once daily or 160 mg twice daily | Long-term use described as possible |
| STEP trial [2] | CO2 extract | 320 mg (160 mg twice daily) | 1 year |
| CAMUS trial [3] | Ethanol extract (85-95% fatty acids) | 320 mg, then 640 mg, then 960 mg | 72 weeks |
| Korean pilot trial [9] | Saw palmetto oil | 320 mg | 12 months |
The common thread is 320 mg a day of a standardized extract. Higher doses were tested in CAMUS and did not add benefit, and they did not add side effects either [3].
Timing and How to Take It
- With food. The EMA notes that stomach complaints such as nausea or abdominal pain can occur, especially when it is taken on an empty stomach [5]. Taking it with a meal is a simple way to reduce that.
- Once or split. Studies used either one 320 mg dose or two 160 mg doses a day [2][5]; there is no evidence that one schedule works differently from the other.
- Check the extract, not just the milligrams. Brands and batches vary in potency [6], so a stated fatty acid percentage is more informative than a bare milligram number.
- Tell your clinician. Mention it at checkups and before any lab work or procedure.
Pumpkin Seed and Green Tea: What Is Studied
Pumpkin seed
Pumpkin seeds are a nutritious food. One ounce of roasted pumpkin seeds provides about 2.2 mg of zinc, roughly 20% of the Daily Value [10]. If you want to read more about that mineral, see our article on zinc and the prostate and our overview of minerals and immune function.
The largest trial is the German GRANU study, which randomly assigned 1,431 men aged 50-80 with urinary symptoms to pumpkin seed (5 g twice a day), pumpkin seed extract capsules (500 mg twice a day), or placebo for 12 months [8]. The extract did not differ from placebo on the main response measure (a drop of at least 5 points in symptom score). Whole pumpkin seed did better than placebo (58.5% vs 47.3% responders), but the authors called this difference descriptive and said a confirmatory study or systematic review is needed before recommending it [8]. Both products were well tolerated.
A small 12-month Korean trial in 47 men tested pumpkin seed oil (320 mg a day), saw palmetto oil (320 mg a day), the two combined, or placebo [9]. The authors reported improvements in symptom scores from each group's own starting point, but the trial was too small to settle anything, and the authors concluded that combining the two oils did not significantly improve any measure [9].
Bottom line: one large trial with mixed results, at food-sized amounts (10 g of seed a day).
Green tea
Green tea comes from the leaves of Camellia sinensis, steamed or pan-fried and dried without fermentation [11]. Its main polyphenols are catechins, especially EGCG [12]. NCCIH notes that although many studies have been done on green tea and its extracts, definite conclusions cannot yet be reached for most of the purposes it is used for [11]. We did not find controlled human trials showing that green tea improves urinary comfort in men, so we make no claim for that use. See our guide to green tea supplements for forms and quality.
Green tea extracts are not the same as a cup of tea. EFSA found that 800 mg or more of EGCG a day from supplements raised liver enzymes in clinical trials [12], and NCCIH reports rare liver injury, mainly with concentrated extracts in capsule or tablet form [11].
Stacking Notes
Saw palmetto is frequently combined with other botanicals such as pygeum, nettle and pumpkin seed. The Cochrane review found the evidence for these combinations to be low certainty, with results that may be little different from placebo [4], and in the small Korean trial the authors concluded that combining saw palmetto oil with pumpkin seed oil did not significantly improve any measure [9]. For general guidance on habits that support healthy aging, see our article on nutrition for healthy aging.
How OPA Prostate Formula Compares With the Studied Dose
OPA Prostate Formula is a 60-capsule, 30-day men's wellness supplement formulated for adults who want daily prostate and overall male health support. A serving is 2 capsules and lists 200 mg of saw palmetto extract, along with pygeum africanum powder (100 mg), a plant sterol complex (50 mg), zinc (12.5 mg), selenium (55 mcg), vitamin E (30 IU), vitamin B6 (2.4 mg), copper (4 mg), a botanical support blend that includes green tea extract, and a 176 mg proprietary blend that includes pumpkin seed. It contains soy.
For an honest comparison: 200 mg of saw palmetto extract per serving is less than the 320 mg a day used in the major trials and the EMA monograph [2][3][5], and the listing does not state the extract's fatty acid percentage. The pumpkin seed and green tea in the formula are part of blends without individual amounts, so they cannot be compared with study doses such as the 10 g of seed a day in GRANU [8]. Because full-dose trials found no advantage over placebo for urinary symptoms [3][4], think of any saw palmetto product as an optional part of a wellness routine, not a fix for symptoms. Review the full label with your clinician, especially if you take other supplements that contain zinc or copper.
Safety and Interactions
Side effects
Saw palmetto is well tolerated and has been used safely in studies lasting up to 3 years [1]. Side effects are mild and infrequent and may include digestive symptoms, dizziness and headache [1]. The EMA lists abdominal pain and headache as common, and nausea, skin rash, raised liver enzymes and reversible breast enlargement in men as uncommon [5]. In the Cochrane review, adverse events occurred at about the same rate as with placebo [4].
Bleeding and blood thinners
The EMA reports a few cases of suspected interactions with warfarin, with increased INR values [5], and a published case report describes severe bleeding during surgery in a man taking saw palmetto, with a prolonged bleeding time that returned to normal after he stopped it [13]. Talk to your doctor or pharmacist before using saw palmetto if you take warfarin or another anticoagulant or antiplatelet medicine, and tell your surgical team you take it before any procedure.
Hormone-related medicines
Because saw palmetto acts on 5-alpha-reductase enzymes in lab studies [6][7] and the EMA lists reversible breast enlargement as an uncommon effect [5], talk to your doctor or pharmacist before using it if you take hormone-related medicines, such as testosterone, prescription 5-alpha-reductase inhibitors, estrogen therapy or hormonal contraceptives. Formal interaction studies are lacking.
Pregnancy, breastfeeding and women
Saw palmetto may be unsafe during pregnancy or breastfeeding [1]. The EMA monograph lists no relevant use for women, children or adolescents [5].
PSA testing and getting checked
Saw palmetto does not appear to change PSA readings, even at higher-than-usual doses [1]. The EMA advises seeing a doctor if symptoms worsen or if fever, blood in the urine, painful urination or difficulty emptying the bladder occur [5]. Men with new or changing urinary symptoms should have them evaluated by a clinician and discuss whether PSA testing is right for them, rather than self-treating.
Pumpkin seed and green tea safety
Pumpkin seed and pumpkin seed extract were well tolerated in the GRANU trial [8]. Green tea as a beverage has no reported safety concerns for adults, but it contains caffeine; green tea extracts can cause nausea, constipation, stomach discomfort and increased blood pressure, and rare liver injury has been reported [11]. Talk to your doctor or pharmacist before using green tea extracts if you take nadolol, atorvastatin or raloxifene, which green tea can affect [11]. If you use a green tea extract, check its EGCG content, since EFSA linked 800 mg or more a day from supplements to raised liver enzymes [12]. Total zinc from all supplements should stay under the adult upper limit of 40 mg a day [10].
Frequently Asked Questions
Does saw palmetto help with urinary comfort in men?
In the best-designed trials, no more than a placebo. The STEP and CAMUS trials and a Cochrane review of 27 studies found little to no difference from placebo in urinary symptom scores or quality of life, even at three times the usual dose [2][3][4].
How much saw palmetto was used in studies?
Most trials used 320 mg a day of a standardized extract, taken as one dose or as 160 mg twice a day [2][5]. The CAMUS trial went up to 960 mg a day without added benefit or added side effects [3].
Does saw palmetto affect a PSA test?
According to NCCIH, saw palmetto does not appear to affect PSA readings, even at higher-than-usual amounts [1]. The STEP trial also found no change in PSA over a year [2].
Can women take saw palmetto?
Saw palmetto may be unsafe during pregnancy or breastfeeding [1], and the EMA lists no relevant use for women [5]. Women should talk to a clinician before using it.
Is pumpkin seed or green tea better studied than saw palmetto?
No. Pumpkin seed has one large one-year trial in which whole seed (10 g a day) did somewhat better than placebo but the extract did not, and the authors said confirmation is needed [8]. Green tea has no solid human trials for urinary comfort [11]. Saw palmetto is the most studied of the three.
How long were saw palmetto studies, and is long-term use safe?
Major trials ran from about 3 months to 72 weeks [3][4], and NCCIH notes saw palmetto has been used safely in studies for up to 3 years [1]. Long-term safety looks reassuring, but long-term benefit has not been shown [4].
Sources
- National Center for Complementary and Integrative Health. Saw Palmetto. NCCIH, National Institutes of Health.
- Bent S, Kane C, Shinohara K, et al. Saw palmetto for benign prostatic hyperplasia. N Engl J Med. 2006.
- Barry MJ, Meleth S, Lee JY, et al. Effect of increasing doses of saw palmetto extract on lower urinary tract symptoms: a randomized trial. JAMA. 2011.
- Franco JV, Trivisonno L, Sgarbossa NJ, et al. Serenoa repens for the treatment of lower urinary tract symptoms due to benign prostatic enlargement. Cochrane Database Syst Rev. 2023.
- Committee on Herbal Medicinal Products. European Union herbal monograph on Serenoa repens (W. Bartram) Small, fructus. European Medicines Agency. 2015.
- Scaglione F, Lucini V, Pannacci M, et al. Comparison of the potency of different brands of Serenoa repens extract on 5alpha-reductase types I and II in prostatic co-cultured epithelial and fibroblast cells. Pharmacology. 2008.
- Fagelman E, Lowe FC. Saw palmetto berry as a treatment for BPH. Rev Urol. 2001.
- Vahlensieck W, Theurer C, Pfitzer E, et al. Effects of pumpkin seed in men with lower urinary tract symptoms due to benign prostatic hyperplasia in the one-year, randomized, placebo-controlled GRANU study. Urol Int. 2015.
- Hong H, Kim CS, Maeng S. Effects of pumpkin seed oil and saw palmetto oil in Korean men with symptomatic benign prostatic hyperplasia. Nutr Res Pract. 2009.
- Office of Dietary Supplements. Zinc: Fact Sheet for Health Professionals. National Institutes of Health.
- National Center for Complementary and Integrative Health. Green Tea. NCCIH, National Institutes of Health.
- EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS), Younes M, Aggett P, et al. Scientific opinion on the safety of green tea catechins. EFSA J. 2018.
- Cheema P, El-Mefty O, Jazieh AR. Intraoperative haemorrhage associated with the use of extract of Saw Palmetto herb: a case report and review of literature. J Intern Med. 2001.
Disclosure: OPA Nutrition sells supplements, including products mentioned in this article. This content is for education only and is not medical advice. Statements about dietary supplements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. Talk to your healthcare provider before using any supplement, especially if you take medication or have a medical condition.
Written and reviewed by Michael Gonzales, Founder, OPA Nutrition · Last reviewed: · How OPA researches and writes
