"I don't think any herb is good or bad. It's how we use it," said Dr. Brent Bauer, director of the Complementary and Integrative Medicine Program at the Mayo Clinic. "Sometimes people take too much. They think, if two is good, then 20 must be better."
Here's a list of herbs and supplements that can be dangerous if taken the wrong way: either in high doses, in combination with certain drugs or before surgery.
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* MayoClinic.com: How herbal supplements can interfere with surgery
1. St. John's wort
This herb, often taken to relieve depression, is always at the top of the list of potentially problematic natural remedies because it can cause serious side effects and increase or decrease the potency of many medications. The Mayo Clinic recommends that many people should avoid it, including those taking antidepressants, anti-blood-clotting drugs, certain asthma drugs, immune-suppressing medications or steroids.
2. Kava
A sedative herb, kava is associated with serious liver problems, even when taken for a very short time, according to the Mayo Clinic. It's especially risky if you're taking drugs to lower cholesterol.
3. Fish oil
Though it's a very safe supplement to increase your intake of heart-healthy fat, Lee says she's seen patients have excessive bleeding when taking high doses of fish oil. "It's not life-threatening, but for example, I've seen where people are taking too much fish oil, and they'll have prolonged bleeding from acupuncture needles."
How much fish oil is too much? More than 5 grams -- or 5,000 milligrams -- a day, according to Bauer.
4. Artemisinin
Last week's Morbidity and Mortality Weekly Report, put out by the Centers for Disease Control and Prevention, details the case of a man who developed hepatitis after taking the herb artemisinin for stomach problems. There was no other reason for his hepatitis, and the disease went away when he stopped taking the herb, and the authors suggested that doctors be aware of a possible relationship between the artemisinin and hepatitis.
5. Various herbs when taken before surgery
Dr. David Rowe, a plastic surgeon, was operating on a patient when he noticed an unusual amount of bleeding.
"The tissue was just oozing, and we couldn't figure out why," he remembered, noting that the patient had told him he wasn't taking any supplements. "After the surgery I asked the patient, 'Are you sure you're not taking anything?' and he said, 'Oh, yes, I'm taking this, this and this.' "
In a paper published this year in the Aesthetic Surgery Journal, Rowe listed about a dozen herbs that should be avoided within two weeks of surgery, including common ones such as garlic, ginseng and echinacea. Some increase bleeding and some affect the heart, and others interfere with anesthesia or other drugs.
It's imperative that you tell your surgeon absolutely every natural remedy you're taking, says Rowe, an assistant professor of plastic surgery at University Hospitals Case Medical Center in Cleveland. Studies have shown that 60 to 70 percent of patients don't tell their physicians about supplements.
