Online Extra: The Straight Dope on Herbs

Dr. Stephen Bent has been investigating saw palmetto and other natural supplements. So far, the results mostly have been disappointing

Do herbal medicines work? Dr. Stephen Bent has been trying to find out. A professor at the University of California at San Francisco and researcher at a San Francisco Veterans Affairs Medical Center, Bent has conducted clinical trials with kava, valerian, and a Chinese herbal remedy.

Later this month, he will report the results of one of the first large randomized, controlled trials to be funded by the National Institutes of Health. The purpose: to determine whether saw palmetto extract, from the berries of the saw palm tree, can help relieve symptoms caused by enlarged prostate.

BusinessWeek Science Correspondent John Carey has spoken with Bent several times, most recently on May 9, 2005. Here are excerpts from those interviews:

Q: Why did you decide to study herbal supplements?


I've always been interested in alternative therapies. I came into it thinking that mainstream medicine doesn't really address all of people's needs. A lot of times, when people come into their doctors' offices, what they get doesn't increase their quality of life.

And of all the alternative therapies, herbs are the easiest to study. It was an easy place to start.

Q: What have you studied?


I did a big study of 10 Chinese herbs [supposed to boost memory and energy in the elderly]. It was a negative study. I looked at kava, which is used for anxiety. That also didn't work.

The main thing I've been doing now is a big study on saw palmetto. The results will be presented at the American Urological Assn. meeting on May 25.

Q: I know you can't describe the results yet, but I understand that there probably will be some positive effects in relieving symptoms of enlarged prostates. If it does work, does that make saw palmetto an exception among herbal supplements?


Unfortunately, I've sort of come to the realization that while there are some effective herbs, the majority probably don't work [in a medicinal fashion].

Q: Some examples?


There was a study with ginkgo asking how it worked [to increase memory and cognition] in elderly people without dementia. It was negative. There were two big studies of Saint-John's-wort and depression. Both were negative.

With vitamin E, a recent meta-analysis showed that in higher doses, it might have a harmful effect for cardiovascular disease.

There have been lots of small studies that have been suggestive [showing potential benefits]. But when big studies have been done, they have been negative.

Q: Then there are also worries about interactions with herbal supplements and prescription drugs, as well as potential harmful effects.


In general, very little is known about the side-effect profiles of most of these medicines. So a big safety net is missing there. We know that Saint-John's-wort interacts with P450 [liver enzymes that break down drugs in the body], affecting everything from oral contraceptive pills to chemotherapy.

There's a concern that some other herbs might cause problems. We did a systematic review of ginkgo for bleeding. There's some convincing evidence that the use of ginkgo led to bleeding. If it does cause increased bleeding, that could be a big problem.

Q: The herbal product that has the most potential for harm is ephedra. You analyzed reports to the American Association of Poison Control Centers that showed that ephedra seems to be 100 times more risky than the next most dangerous supplement, kava. And the Food & Drug Administration banned supplements containing ephedra, only to have the ban overturned by a federal judge in Utah earlier this year. What does this mean about oversight of these products?


The FDA spent a lot of time trying to ban ephedra, only to have the ruling that they don't have authority [to ban it] at lower doses. That says a lot about the difficulty the FDA is having regulating herbal products.

Q: So overall, it doesn't sound like herbs are very useful as medicines.


There are two ways to spin it. One way is that if you look at the top 10 selling herbs, there is not strong evidence that they work. Yet one-third of drugs come from plants. So there are good things out there. We need to figure out where they are and how to [find the more effective ones].

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