Research News

Study Casts Doubt on Saw Palmetto as Prostate Remedy

  • Playlist
  • Download
  • Embed
    <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

A new study in The New England Journal of Medicine indicates "saw palmetto" does not work to shrink enlarged prostates. At least 2 million men take the supplements, often on the advice of doctors. Smaller studies have shown that saw palmetto does work, but this is the largest study to date.


This is MORNING EDITION from NPR News. I'm Steve Inskeep.


And I'm Renee Montagne.

We're going to look now at treatments for two different medical conditions. Coming up, a report on a federal review of remedies for Attention Deficit Hyperactivity Disorder. First, there's news today about a popular prostate treatment. Results of a new clinical trial cast doubt on the effectiveness of the herbal supplement, saw palmetto. NPR's Allison Aubry has more.


For men over 50, an enlarged prostate is about as common as gray hair. In all men, the gland grows larger over time, and for many, this brings problems with urination. Men reporting having to get up several times a night to hit the bathroom, and when they seek treatment, what many turn to first is the over- the-counter supplement, saw palmetto. Urologist Ron Morton says a lot of his patients try it.

Dr. RON MORTON (Urologist): Many men come in taking saw palmetto, and what I tell those men is that we don't have any evidence that it's not safe for them, but we also don't have tremendous evidence that it will do them any good with respect to their voiding symptoms.

AUBREY: Researchers at the University of California, San Francisco wanted to help settle the question, to say more definitively whether saw palmetto is effective. So, they recruited a couple hundred men with moderate to severe symptoms, and asked them to take two capsules a day for one year. Some of the capsules, the men were told, would contain the real deal, an active dose of saw palmetto berry extract. Other capsules would be placebos, filled with a goo that smelled like saw palmetto, but contains nothing active.

Dr. STEPHEN BENT (Researcher at University of California, San Francisco): We had, at the very beginning of the study, everyone took placebo for a month. They didn't know that that was the case, that they were on placebo for a month, and during that time period, they improved by one and a half points in the symptoms score.

AUBREY: Meaning everyone improved, even though what they were swallowing was just an inert goo. Researcher Stephen Bent says the improvement was very modest. The symptoms score came from a self-administered questionnaire given to the men. It included seven questions that gauged severity of symptoms. And Bent says a one and half point change is not considered much.

Dr. BENT: Just for perspective, it's been determined that about a 3 point change is what's considered clinically detectable.

AUBREY: Meaning that's when patients perceive they're feeling better. Given the changes seen in the first month of the study with the placebo capsules, what researchers expected to find were more significant changes in symptom scores when they gave some men the real saw palmetto supplement. But that's not at all what happened.

Dr. BENT: During the entire rest of the 12 months of the study, they only improved by about a half of a point, and it was the same improvement in both groups. So really, in our study, there was no difference in the change in symptoms in men taking saw palmetto, or those taking placebo.

AUBREY: A finding that Bent's team had not anticipated.

Dr. BENT: We were surprised and a bit disappointed. You know, we had sort of hoped that this would validate prior work, and that this would make this sort of a mainstream, useful herbal product.

AUBREY: Nearly a dozen prior studies had found saw palmetto to be mildly effective in relieving symptoms. But none was considered conclusive. Some were very small, others were short in duration. And Stephen Bent says, in some cases, researchers didn't seem to truly blind their subjects. They used placebo capsules made from olive oil that didn't have the pungent smell or look of saw palmetto.

Dr. BENT: We thought that it would be quite easy for a patient who was taking placebo to sort of peak into their capsule or poke it open and realize that it was unlikely to be an active substance. So, we took very great care to use a substance that was very bad tasting, and the dark color, so that it mimicked saw palmetto.

AUBREY: The careful methodology does not mean the study is perfect, but family physician Wendy Biggs says the results will change the way she recommends saw palmetto.

Dr. WENDY BIGGS (Family Physician): I actually gave a lecture yesterday on herbal medicine, and this was one of the ones that I said, and this is shown to work. Now today, I'm going, oh, I'm going to have to change my mind after reading the new article.

AUBREY: Biggs says there's nothing in the study to suggest that saw palmetto is harmful to men, so she won't take patients off the supplement if they're finding it helpful. But if the placebo pills are as effective as the real supplement...

Dr. BIGGS: I almost wonder, do we just give placebo? I mean, it sounds funny...

AUBREY: But it reinforces the idea that when people think they're taking something that's supposed to make them feel better, they often do feel better. Researcher Stephen Bent says his findings, published in the current issue of the New England Journal of Medicine, should not be the final word on saw palmetto. It's possible that the capsules used in his study didn't contain the right amount of active ingredients. What's needed is another well defined study.

Dr. BENT: To ether confirm or contradict these findings.

AUBREY: In the meantime, urologist Ron Morton says men experiencing enlarged prostate symptoms have several other choices. There are two kinds of FDA approved prescription drugs. And when those don't work, another option is a minimally invasive laser surgery.

Allison Aubrey, NPR news, Washington.

Copyright © 2006 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by a contractor for NPR, and accuracy and availability may vary. This text may not be in its final form and may be updated or revised in the future. Please be aware that the authoritative record of NPR’s programming is the audio.



Please keep your community civil. All comments must follow the Community rules and terms of use, and will be moderated prior to posting. NPR reserves the right to use the comments we receive, in whole or in part, and to use the commenter's name and location, in any medium. See also the Terms of Use, Privacy Policy and Community FAQ.

NPR thanks our sponsors

Become an NPR sponsor

Support comes from