4 Herbal Supplements Your Doctor Hates

Herbal remedies may seem safer than drugs. But experts have concerns about these popular supplements.

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More than half of Americans have taken a dietary supplement, and it's easy to see why. Popping a pill is painless. Supplements don't require a prescription from a doctor. And there's always some hale bloke out there who will vouch for the miraculous health improvements he experienced while taking this or that herbal remedy. 

Plus, herbals often seem safer than drugs and other treatments. If a supplement can be found on stores' shelves alongside healthy foods, it must be wholesome, right?

Wrong. Of the 30,000 products rated by the Natural Medicines Comprehensive Database, an independent research and publishing organization, less than one percent earned a top score for safety, effectiveness, and quality. 

[Read: 10 Things the Food Industry Doesn't Want You to Know.]

Unlike prescription medications, dietary supplements aren't reviewed or approved by the FDA before they go on sale. And, although manufacturers have been required to prove that new supplements are "reasonably expected to be safe" since 1994, a recent report in the New England Journal of Medicine found that this law is largely unenforced.

"Consumers have the idea that the people who are selling herbal remedies are doing it out the goodness of their hearts," says Lauren Streicher, assistant professor of obstetrics and gynecology at Northwestern University's Feinberg School of Medicine. But supplement makers are even more profit-driven than pharmaceutical companies, which are subject to FDA review, she says. "Does the FDA make mistakes? Yes. But they're the only protection we've got to make sure greed doesn't get in the way of science."

While most supplements will do more harm to your wallet than to your body, others are downright dangerous. Here are four herbal supplements doctors love to hate.

[Read: Do You Need Vitamins and Supplements?]

St. John's Wort. Among health care professionals, St. John's wort has a lousy reputation. While some research suggests it may be useful as a treatment for mild forms of depression, other large studies have concluded it's no more effective than a placebo when treating major depression of moderate severity. Some consumers take St. John's wort for other conditions, like anxiety and sleep disorders, but there's little if any evidence it works for those conditions. What's more, the herb can make prescription drugs less effective or more dangerous because it changes the way the body processes all kinds of medications, from to antidepressants to birth control pills.

"That's the real danger. Because it affects the way the liver metabolizes drugs, it's going to interfere with metabolism of other drugs," explains Gerard Mullin, director of integrative gastrointestinal nutrition services at the Johns Hopkins Hospital and author of The Inside Tract: Your Good Gut Guide to Great Digestive Health.

[Read: 7 Common Digestive Problems and How to End Them.]

If you're committed to experimenting with St. John's wort, keep your doctor in the loop. He or she can monitor your symptoms and help you make sure you're not undermining the effectiveness of the rest of your treatment regimen.

Yohimbe. The bark from the Yohimbe tree, native to western Africa, can be found in teas, capsules and tablets promoted to treat sexual dysfunction. Because the bark contains a chemical called yohimbine, which is used in some prescription medications for erectile dysfunction, it may seem like a natural and prescription-free alternative to a better sex life. But the herb can cause high blood pressure, rapid heart rate, tremors and, at high doses, serious heart problems and even death. As far back as 1993, the FDA warned of its potentially serious side effects. More recently, Consumer Reports lists it as one of the "dirty dozen" supplements to avoid. And yet, its exotic image and global presence still tempt shoppers who turn to the internet—rather than their doctor or pharmacist—to quell their bedroom woes.

Black Cohosh. Streicher, who treats mostly middle-aged women, knows that menopause can cause desperation for symptom relief. That's why many women going through it turn to black cohosh, an increasingly popular herbal supplement purported to ease menopause-associated symptoms like hot flashes, night sweats, and vaginal dryness. Some short-term clinical trials have concluded that it's superior to a placebo. A year-long trial, however, found the herb to be no more effective than a placebo in treating hot flashes and night sweats.