The New Herbal Outcasts
Although herbs have been used for centuries, there are some very common herbs whose possible toxic reactions have begun to be noticed only recently. Unfortunately, every time an herb is even remotely connected with toxicity, it makes headlines. At the same time, side effects and deaths from pharmaceutical drugs generally receive less media attention. Actually, toxicity from medicinal herbs pales in comparison with injuries resulting from prescription drugs and even vitamin supplements. For example, according to the Consumer Product Safety Commission in Washington, D.C., six children died in the United States in 1993 and three in 1994 as a result of taking products that contained iron. No deaths have been reported from the low doses in children's chewable vitamins.I suspect that some undiscovered factors cause certain people to be more susceptible to certain herbs than others. Researcher and herb toxicity specialist Ryan J. Huxtable, Ph.D., who works at the Department of Pharmacology at the University of Arizona, notes that taking anticonvulsant drugs with the herbs comfrey, coltsfoot or senecio increases the toxicity of certain compounds found in the herbs.
Simon Mills of the Centre for Complementary Health Studies at the University of Exeter in England also found evidence of complications when certain pharmaceutical drugs and an herb were taken at the same time. Mills reported on one woman who developed liver toxicity while taking the drug Indapamide in combination with various herbs, including germander. Another woman suffered the same effect with a Lorazaepam/herb combination that may also have included germander. A third case involved a group of Native Americans who were poisoned after eating a species of Heliotropium; it was discovered that the two who died were also taking phenobarbital to treat epilepsy.
An existing medical condition may also make you more susceptible to the side effects of certain herbs. An example is a thirteen-year-old boy who developed liver dysfunction after eating comfrey regularly for about three years—he may have been more susceptible because he had an inflammatory bowel disease. There are also cases of people developing liver problems while taking chaparral and senna to correct skin problems, but this connection is less clear—skin problems are often related to existing liver imbalances.
In one laboratory study, when experimental animals were fed a diet that was about one-third comfrey, they developed cancer of the liver. And a few cases of liver damage (although not cancer) were reported in people who had ingested large amounts of comfrey. The offending agent in comfrey has been identified as pyrrolizidine alkaloids. More than 200 types of these compounds are found in various other plants as well, including the medicinal herbs coltsfoot, borage, lungwort, senecio and dusty miller. (Borage seed oil contains such small traces of these compounds that it is considered safe.) When animals were fed large amounts of the pure pyrrolizidine alkaloids derived from coltsfoot, they experienced liver toxicity. In 1987, after a woman who drank tea that included coltsfoot gave birth to an infant with severe liver injury, Germany banned any herb containing these alkaloids.
Most medical researchers assume that comfrey is perfectly safe if used externally—for instance, in poultices and salves—but are wary of using it internally, even though practically no alkaloids are found in the dried leaves. Comfrey's fresh root is especially potent—about ten times stronger than the fresh leaves. Germany and France permit the use of comfrey for external use on unbroken skin. Canada allows the sale of only the species that do not contain the strongest alkaloids, such as Symphtum officinale. According to experiments done in Sweden, boiling herbs containing pyrrolizidine alkaloids in water for 20 minutes makes them nontoxic; nevertheless, Sweden classifies both comfrey and coltsfoot as drugs. Until herbs containing these compounds receive a clean bill of health, it is best not to take them for internal use but to rely on other herbs instead.
Another herb in question is chaparral. People take it because it contains NDGA (nordihydroquaiatetic acid), a strong antioxidant and anti-cancer agent. Herb industry surveys show that more than 200 tons were sold in the United States between 1970 and 1990. And during this time, there was not a single complaint of side effects arising from the use of this herb. When two to three cups of chaparral tea or the isolated NDGA were given daily to more than 50 cancer patients, the only side effects were occasional nausea or diarrhea. Very large doses resulted in lowered blood pressure. These and other studies led the National Cancer Institute to state in 1989 that "acute toxicity of NDGA is not great."
With all of these essentially positive reports, FDA chemists, who still have not found any liver toxicity in chaparral, were puzzled when a woman developed hepatitis after taking it for three months to treat breast lumps. It turned out that she was downing a whopping 15 tablets a day—far in excess of the recommended dose. This story did not attract much attention until 1992, when three people who were taking two or three tablets daily developed liver problems that did not go away until they discontinued the herb. As a result of these cases, the FDA issued a public warning that a "casual relationship" exists between chaparral and liver problems.
The herb germander also seems to be problematic. In France, seven people came down with acute cases of hepatitis while taking capsules or a tea of wild germander to lose weight. All seven recovered after discontinuing the herb, but three of them developed signs of liver problems as soon as they resumed taking it—researchers suspect that the problem was the result of an allergic reaction. Because of this situation, French manufacturers voluntarily stopped marketing germander; in 1982 the government banned its use.
The root bark of sassafras contains the compound safrole, which is banned by the FDA for use in food, along with sassafras. This ban was instituted in 1960, after laboratory animals developed cancer when injected with large amounts of safrole. The flavoring used in root beer must be "safrole-free." Smaller amounts of safrole are also found in black pepper, star anise, basil, cinnamon leaf, nutmeg, sage and witch hazel, but so far these herbs have not come under fire.
The results of some studies suggest that comfrey, coltsfoot and sassafras may have anti-cancer properties—in one study, a comfrey leaf tea was shown to decrease tumor growth. Bruce Ames, Ph.D., Chairman of the Biochemistry Department, University of California, Berkeley, has said that the risk of one cup of root tea is comparable to that of a peanut butter sandwich, a diet soda containing saccharin and one raw button mushroom. Mice given an extract made from the whole comfrey plant had their immune systems stimulated. When people were given small doses of safrole, it did not create any cancer-producing substances. This led researchers to suggest that the toxic reaction in humans is different from that in rats. It seems that we have much more to learn about determining herbal toxicity.