For the millions of American men with enlarged prostates, few remedies may sound more appealing than the dietary supplement known as saw palmetto extract. 

The chemical comes from a palm-leaf plant of the same name that grows in the Southeastern U.S., and it has been used to treat urologic conditions since ancient times. 

In modern times saw palmetto is readily available online or at any drugstore. In ad after ad it promises to relieve the frequent or painful urination that sends many men rushing to the bathroom multiple times per night. 

More on Vitamins & Supplements

Consumers shelled out $152 million in 2016 for saw palmetto products, according to the Nutrition Business Journal. But just because it’s popular doesn’t mean it works. 

“Saw palmetto for prostate issues is one of the classic examples of supplement snake oil,” says Pieter Cohen, M.D., an assistant professor of medicine at Harvard Medical School who has studied supplements extensively. “It’s touted all over the place, and there is zero evidence that it actually works.” 

Here are five reasons you should skip this supplement and head to the doctor for advice instead:

1. Your Underlying Medical Issue

The clinical diagnosis for an enlarged prostate gland is benign prostatic hyperplasia (BPH), and it’s the most common cause of frequent urination or urinary pain in men. 

But these symptoms don’t always mean that your prostate is enlarged. It could be inflamed or infected—a condition known as prostatitis that requires antibiotics. Your urinary troubles could also be a side effect from another medication. 

Taking an over-the-counter supplement without having a doctor find and address the true source of your symptoms is dangerous, even if it provides temporary relief. 

2. Supplement Safety Concerns

Dietary supplements such as saw palmetto are not regulated the same way that prescription drugs are. Supplement makers are not required to prove to federal regulators that their products are safe, that they’re effective, or that they’re accurately labeled. 

Multiple studies and investigations have found that such products are often grossly mislabeled: They may be illegally spiked with prescription drugs, which can interact in potentially dangerous ways with other medications you may be taking. And in many cases the amount of active ingredient is either far less or far greater than what the label indicates. (One study analyzed six brands of saw palmetto and found that half of them contained less than 20 percent of the amount stated on the label.)

3. The Placebo Effect

In one scientific study, researchers gave 369 men suffering from symptoms of BPH either a placebo or doses of saw palmetto extract. They tracked their symptoms for up to 72 weeks and concluded that the extract (even at high levels) was no better than a placebo at alleviating symptoms. Several similar studies have also reached that conclusion, and a thorough review by the independent Cochrane Collaboration of studies involving a total of 5,666 men found this lack of efficacy, too.

4. The Alternatives

If you’re trying to avoid taking prescription medications or are undergoing surgery to resolve your prostate problems, you can try other things that, unlike saw palmetto, are recommended by doctors: 

  • Cut back on drinks between dinner and bedtime, especially alcoholic and caffeinated beverages.
  • Limit the use of antihistamines and decongestants, which can prevent muscles around the bladder from relaxing.
  • If you take a diuretic for high blood pressure, ask your doctor about changing the time you take it, reducing the dose, or trying a different drug.
  • Eat lots of produce, which may also help, according to a large study done in 2007. 

5. The Cost

In the short term, saw palmetto and other dietary supplements might sound like a great way to save money: They promise quick relief without a trip to the doctor’s office and a costly prescription. One bottle, containing 250 capsules, costs about $20. 

But if those capsules don’t work (or if they provide relief without addressing your underlying medical problem), it may cost you much more time and money to fix the problem in the long run. You may also seriously endanger your health, which is priceless.