Saw palmetto is a supplement made from the fruit of the Serenoa repens tree.

It’s often used to treat enlarged prostate, improve urinary function, and enhance hair growth. Some also use the supplement to boost libido and fertility and reduce inflammation. Finally, saw palmetto is claimed to have anticancer effects.

However, not all of its uses and purported health benefits are supported by science.

This article looks at the research behind saw palmetto, including its benefits, potential side effects, and dosage recommendations.

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Saw palmetto, or Serenoa repens, is a dwarf palm tree native to the southeast regions of North America and especially abundant in Florida, Georgia, Cuba, and the Bahamas (1).

It grows in sandy soil and gets its name from the sharp, saw-like teeth on the stalks that attach the tree’s leaves to its stem. The saw palmetto tree produces dark berries that contain a large seed (1).

The saw palmetto fruit is thought to have been used by Native Americans for its nutritional, diuretic, sedative, aphrodisiac, and cough-reducing properties.

Nowadays, the berries are eaten whole or dried and used to make tea. Dried and ground saw palmetto can also be purchased in capsule or tablet form. It’s widely available, including online.

Still, the most common form on the market is oily extracts of the fatty portions of the dried berries (1).

These supplements contain 75–90% fats depending on the extraction method. They typically provide higher amounts of beneficial plant compounds like vitamin E and other antioxidants compared to the raw fruit (2).

Summary Saw palmetto is a supplement made from the fruit of the saw palmetto tree. The supplements come in various forms, with oily extracts being the most popular.

Saw palmetto may help treat benign prostatic hyperplasia (BPH) — a medical condition characterized by a slow, noncancerous yet abnormal enlargement of the prostate.

BPH is common in older men, affecting up to 75% of men in their 70s (3).

If left untreated, the prostate can enlarge to the point of interfering with the ability to properly empty the bladder. It can also increase the frequency and urge to urinate, often causing excessive nighttime urination which may disrupt sleep.

BPH is part of a larger group of lower urinary tract symptoms (LUTS), a group of symptoms typically involving the bladder, urethra, and prostate. Unlike BPH, LUTS can affect both men and women (4, 5).

Several studies have looked at saw palmetto’s effect on LUTS — with mixed results.

Early studies reported that saw palmetto may help increase urine flow and reduce nighttime urination in men with BPH — both when used alone or in combination with traditional drug therapy (6, 7, 8, 9, 10).

However, the latest Cochrane review — the highest standard in evidence-based healthcare — concluded that saw palmetto provides little improvement in LUTS (11).

On the other hand, two reviews note that a daily dose of 320 mg of Permixon — a specific saw palmetto extract — was more effective than a placebo at improving urine flow and reducing nighttime urination (12, 13).

It’s possible that the effects vary based on the strength of the individual formulation. Overall, more studies are needed before strong conclusions can be made.

Summary Evidence related to saw palmetto’s ability to improve prostate health and urinary function is mixed. Some studies report that it may improve urine flow and reduce nighttime urination, but others find no effect. More research is needed.

Saw palmetto may help prevent androgenic alopecia — a type of hair loss also known as male and female pattern baldness in men and women, respectively.

It’s thought to work by blocking the enzyme that converts testosterone to dihydrotestosterone (DHT), an androgen-type hormone believed to cause this form of hair loss (14, 15).

Higher levels of androgen hormones like DHT are thought to shorten the hair growth cycle and lead to the growth of shorter and thinner strands of hair (15).

One small study reports that a daily 200-mg dose of saw palmetto — taken with another beneficial plant compound known as beta-sitosterol — reduced hair loss in 60% of men with androgenic alopecia compared to a placebo (16).

In a 2-year study, men with male pattern baldness were given 320 mg of saw palmetto per day or finasteride, a conventional hair loss medication.

By the end of the study, about one-third of those given saw palmetto reported an increase in hair growth. That said, saw palmetto was only half as effective as the conventional medication (17).

A small study also reports a small increase in hair count in about half of the men treated with a saw palmetto hair lotion. However, this lotion also contained other active ingredients, making it difficult to isolate the effect of saw palmetto (18).

Although promising, the research on saw palmetto’s effect on hair loss is limited. More studies are needed before strong conclusions can be made.

Summary Saw palmetto may help fight male and female pattern baldness. Still, it appears less effective than conventional hair loss medications, and more research is needed to confirm these effects.

Saw palmetto is touted as providing additional benefits — though most are unsupported by strong science.

For instance, test-tube research shows that Permixon – a specific formulation of saw palmetto – may reduce markers of inflammation in prostate cells. However, it’s unclear whether other saw palmetto supplements have the same effect (19, 20).

Permixon may also protect libido and fertility in men. Conventional drug therapy for BPH and LUTS has been shown to negatively impact sexual function in men.

A review of 12 randomized controlled studies — the gold standard in nutrition research — compared Permixon with conventional drug therapy as a treatment for BPH and LUTS.

Though both produced negative side effects on male sexual function, the saw palmetto supplement led to smaller drops in libido and lower impotence compared to the conventional drug treatment (12).

Still, it’s unclear whether Permixon has the same effect in healthy men or whether other saw palmetto formulations offer similar protective benefits.

What’s more, additional studies list decreased libido as a potential side effect of taking saw palmetto supplements — so more research is needed to confirm this (21).

Finally, test-tube research suggests that saw palmetto may help kill and slow the growth of certain cancer cells, including of the prostate. Although promising, not all studies agree, and more research is needed (22, 23, 24).

Summary Saw palmetto may reduce inflammation and protect your body against the growth of cancer cells. However, more research is needed.

Though raw and dried saw palmetto berries have been eaten for centuries, their safety hasn’t been directly studied.

That said, studies suggest that saw palmetto supplements are generally safe for most people. The most common side effects include diarrhea, headache, fatigue, decreased libido, nausea, vomiting, and vertigo. Yet, they tend to be mild and reversible (21).

More serious side effects like liver damage, pancreatitis, bleeding in the brain, and death have been reported in isolated cases. However, it isn’t always clear whether saw palmetto was the cause (21, 25, 26, 27).

Two case studies further report that young girls experienced hot flashes when given saw palmetto supplements to treat hair loss or hirsutism — a condition causing unwanted male-pattern hair growth in women (28, 29).

Moreover, there is some concern that saw palmetto may be linked to birth defects and may prevent the normal development of male genitalia (1).

Therefore, use is strongly discouraged in children, as well as pregnant or breastfeeding women.

What’s more, a review of labels and internet marketing materials cautions people with prostate disorders or hormone-dependent cancers to consult their healthcare provider before taking this supplement (1).

They also warn that saw palmetto may interact with other medications, though additional reviews found no evidence of this (1, 21).

Summary Saw palmetto is generally considered safe. Still, children, pregnant and breastfeeding women, as well as those with certain medical conditions may need to refrain from taking this supplement.

Saw palmetto can be taken in many forms.

Little research exists on effective dosages when the saw palmetto berries are eaten whole or steeped to make a tea.

When taken as a dried supplement or an oily liquid extraction, saw palmetto appears most effective in daily dosages of 160–320 mg (12, 13, 16, 17).

That said, most studies have been done exclusively in men, so it’s unclear whether the same dosages are appropriate for women (1).

Always consult your healthcare provider before taking saw palmetto to ensure your safety and appropriate dosage.

Summary Saw palmetto appears most effective when taken in daily doses of 160–320 mg. However, more studies — particularly in women — are needed.

Saw palmetto is a supplement made from the fruit of the Serenoa repens tree.

It may offer health benefits like improved hair growth, prostate health, and urinary function.

According to test-tube studies, it may also have anti-inflammatory and anticancer properties, but more research in these areas is needed.

It’s best to discuss this supplement with your healthcare provider before giving it a try. Children and pregnant or breastfeeding women should abstain from taking saw palmetto.