People were using herbs and other plants to stay healthy way before pharmaceutical companies showed up with synthetic products and their dangerous side effects. But you know that just because something is “natural” doesn’t mean that it’s safe.

Like synthetic prescription drugs that change body chemistry, herbal products also can hurt your liver, especially if they contain impurities…aren’t really what they claim to be…or are just not used properly. Some herbs have been associated with liver injuries so often that they’ve been banned in the United States. But, in these cases, was the herb itself really bad or were other factors causing the problem?

“Although some of the concerns we are seeing about herbal supplements and liver toxicity are valid, most herbal products pose no harm when taken properly. ‘Properly’ means at the right dosages, for the right reason and for the right length of time,” said naturopathic physician Andrew L. Rubman, ND, founder and medical director of the Southbury Clinic for Traditional Medicine in Southbury, Connecticut.

But the trend, unfortunately, is not making herbal supplements look good. Research compiled from a large database that tracks liver injuries caused by either prescription drugs or herbal supplements shows that the proportion of liver injuries associated with herbal and dietary supplements has increased over the past 10 years from 7% to 20%.

One study based on data from this research summarized the dangers of several different herbs and herbal formulations implicated in liver injuries, so I spoke with Dr. Rubman to get the lowdown on seven commonly known herbs that were on the list. Some of these herbs definitely should be avoided…others used with caution…and others have just gotten a bum rap…

  • Comfrey.

Comfrey has been traditionally used, often in the form of a tea, to soothe an upset stomach. It also has been used topically to treat wounds and skin inflammation because it is rich in tannins and other substances that promote skin repair. But because comfrey contains pyrrolizidine alkaloids, compounds that are toxic to the liver, products containing it that are meant to be drunk or eaten are now banned for nonprescription use in the United States.

Comfrey is now available only in the form of creams and ointments for treatment of skin wounds and inflammation, and because its harmful alkaloids can penetrate the skin, consumers are warned to not overdo use of these products—do not use on open wounds or broken skin and do not use for longer than 10 days at a time or for more than four to six weeks total in one year.

But the concern about comfrey’s liver-harming properties might be overblown, according to Dr. Rubman. Other compounds in the herb that are beneficial to the liver may offset the dangers of the pyrrolizidine alkaloids, he said. Although in Dr. Rubman’s view, the herb could probably be safely used while in the care of a naturopathic doctor who would monitor liver health, there are certainly plenty other safer remedies for soothing an upset stomach.

  • Kava.

Kava comes from the root of a type of pepper plant. On the tropical islands of the Pacific Ocean where the plant is native, kava has been used as a mild intoxicant, similar to alcohol. In Western herbal medicine, however, it has found a place, in pill form, in the relief of anxiety and insomnia. Liver damage, including hepatitis and liver failure, has been associated with kava use. This has led several countries, including the United Kingdom, Poland and France, to restrict or ban it. But researchers have been debating whether kava is, indeed, toxic or whether nontraditional ways of preparing it are causing liver injury.

It’s neither banned nor restricted in the United States. Although the FDA acknowledges that kava is useful for managing anxiety, it has issued a warning that it has been linked to serious liver damage.

According to Dr. Rubman, kava’s predicament is a perfect example of why herbs should be used in their traditional ways. When extracts are prepared in the traditional manner from the entire plant, they are generally safe, he said, but when an isolated chemical from the plant is commercially sold in capsule form, problems can occur. Why? Because other beneficial parts of the plant that act in a check-and-balance way are left out. For this reason, Dr. Rubman may prescribe the kava extract manufactured by Eclectic Institute in Sandy, Oregon, which is produced using the original extraction method. This brand of kava is widely available in nutrition stores and online through,, and other sellers.

  • Green tea extract.

Green tea extract is on store shelves everywhere, frequently marketed as a weight-loss product. But when green tea extract is taken while fasting, as some people using weight-loss supplements may be doing, the liver may be overwhelmed by the high volume of antioxidant compounds, resulting sometimes in serious liver injury.

Taking weight-loss or other potent supplements while fasting is unwise, according to Dr. Rubman. “When someone adopts an unusual diet or fasts, the body’s metabolism is thrown off. The change can cause the liver to go into overdrive to adjust,” he said. “In the case of green tea extract, the same compound that is protective for someone with a normal metabolism can harm someone whose metabolism is not working at its best.” Green tea extract, thus, is normally safe when taken in between meals but should not be part of a fasting or cleansing regimen.

  • Germander.

Germander actually refers to about 250 species of plants in the mint family that have been used to treat high blood pressure, gout, diabetes and other conditions, but it is known to be potentially poisonous to the liver. It should be used only under direct supervision of a naturopathic doctor or other knowledgeable health-care provider who can monitor the supplement’s impact on the liver, according to Dr. Rubman. He cautioned that germander has been finding its way into weight-loss supplements and is also often added to supplements made from skullcap—an herb belonging to the mint family—or even substituted for skullcap in supplements claiming to contain skullcap. This unethical behavior by some supplement companies has put skullcap into a predicament. See the next section for details.

  • Skullcap.

Skullcap, also called asafetida, produces stalks of delicate flowers—usually purple although violet and red varieties also exist. American skullcap (Scutellaria lateriflora) is generally used to calm the nerves and relax muscles. Chinese skullcap (Scutellaria baicalensis) is used to treat allergies, infections, inflammation and headaches. Some studies have suggested that skullcap can cause hepatitis, but it’s not known whether the blame lies with the herb itself or with one of the other products it is often mixed with (or replaced by)—namely germander.

As far as Dr. Rubman is concerned, skullcap is an innocent bystander, guilty only of being associated with or replaced by germander. In this instance, reading labels is not enough. Choosing high-quality supplements and not any eye-catching bottle on a store shelf is essential for your safety. Products manufactured by Eclectic Institute and HerbPharm, are among those Dr. Rubman uses in his clinical practice.

  • Celandine.

From the poppy family, celandine has traditionally been used as a mild sedative and treatment for digestive problems. Blockage of bile ducts and other liver problems can develop in people who regularly use the herb for too long (three months or more). How celandine does its damage, which goes away once celandine use is stopped, isn’t known.

Dr. Rubman has yet to encounter problems with celandine in his practice, but he prescribes the herb only in moderation and not on a regular basis. He also notes that it should be used only under the guidance of a naturopathic physician who will decide what the appropriate dosage for an individual patient is and how long it should be taken.

  • Chaparral.

High in antioxidants, chaparral refers to the leaves of the creosote bush, which is an evergreen shrub native to southwest deserts. Chaparral has been used to treat bronchitis, skin conditions and pain, but it very commonly causes bile ducts to become blocked after three weeks of use. Although the damage usually clears up quickly after chaparral is stopped, severe liver damage, including cirrhosis (a common cause for liver transplantation), has been associated with chaparral. As with green tea extract, an overload of an antioxidant compound may be behind the liver damage caused by chaparral. This is another herb that should be taken only under the guidance of a knowledgeable health-care provider, according to Dr. Rubman.


How would you know if a supplement is hurting your liver? “Fatigue, loss of appetite, looking sick and pale and/or noticing a strong body odor can be signs of liver trouble,” said Dr. Rubman. “You may become gassy, and your stools may be paler than usual.” If you have any of these symptoms, stop taking the supplement and make an appointment to see your doctor as soon as possible. In extreme cases, jaundice may occur. Signs of jaundice include itchiness, yellow eyes and skin, dark urine, and yellow stools. If this happens, get to a doctor—or hospital emergency room—immediately.

“The liver is a very resilient organ,” said Dr. Rubman. If a drug or supplement harms the liver, the damage is frequently—but not always—reversed once you stop taking the offending drug or supplement. To avoid liver problems that might be set off by herbs and herbal supplements, Dr. Rubman’s advice, in addition to taking swift action if the symptoms described above occur, is to not be like the approximately 40% of supplement users who hide use from their doctors. He urges you to tell your health-care provider about everything you’re taking so that your doctor will know what to do to prevent complications—such as not prescribing a drug that might interfere or interact with a supplement.

Most importantly, buy your herbs and supplements from a licensed naturopathic doctor. Naturopathic practitioners have access to the best, professional-grade products that are free from contaminants and sneaky substitutions. And naturopathic professionals can best advise you about the safe and effective use of a botanical remedy.