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5 Risky Herbal Supplements

Even though they're natural, some herbal supplements can be dangerous.


Pennyroyal (Mentha pulegium) has not been proven effective for any suggested uses. It was traditionally used to cause abortion, but the large doses required for this could kill the mother or cause irreversible damage to the liver and kidneys, according to the National Institutes of Health.

According to the National Institutes of Health, pennyroyal oil is considered unsafe for anyone at any dose, and it is unknown whether the tea is safe.

"It's a mint, and you don't get that much poison in a tea, but I wouldn't risk it. Go for spearmint. Why go for the liver-toxic mint?" Fugh-Berman says.

Listed in the FDA's poisonous plant database in 1997, pennyroyal can be found online in many forms, including oil.

How Can I Choose a Safe Herbal Supplement?

These are steps everyone should take before taking any herb, says Tod Cooperman, MD, who is president of ConsumerLab, which tests the safety and quality of dietary supplements.

Do your homework. Before starting any herbal medicine, find out:

  • Is it safe?
  • Does it work?
  • What dosage works?
  • What part of the plant works? (root, stem, leaf)

Talk to your health care team. Tell all of those involved in your health care -- physical and mental health -- that you're considering taking an herbal supplement. Discuss whether the supplement is safe and effective in general and for you specifically. Remind health care providers of any conditions you have and any prescription or over-the-counter medications you take. Don't wait for them to ask.

Get a quality product. Check the label for the plant's common and Latin names and the plant part used, Weil advises. If it's the root that's effective, you won't benefit from tablets made from the stem.

Look for a quality seal. "Herbals are the most likely of all supplements to contain contaminants," Cooperman says. The three major quality seals are the USP seal (US Pharmacopeia), the NSF seal (National Sanitation Foundation), and the CL seal, issued by Cooperman's Consumer Lab. 

Each of these seals indicates that the product ingredients match the label and that if there are contaminants present, they do not exceed safe levels. USP and NSF make sure the product meets Good Manufacturing Practices set by the FDA.  CL holds products to standards set by the state of California, which are more stringent than the FDA's standards, Cooperman says. USP and CL also verify that supplements will break apart in the body. 

Go for supplements made by big companies, McQueen suggests. Major store brands or manufacturers of FDA-regulated drugs are the most likely to adhere to quality standards.

Test tablets. "Typically herbals are powders in capsules that you don't need to worry about, but make sure tablets will break apart and release ingredients in your body," Cooperman says.  Put the pill in body-temperature water and give it about 45 minutes to fall apart. "If it stays intact, it's likely doing the same thing in your body," Cooperman says.

Reviewed on October 25, 2011

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