Counseling Sheet

Dangerous Herbs

Agatha M. Thrash, M.D.
Preventive Medicine

With the medicinal use of herbs coming more and more into vogue in today's society, it behooves everyone who uses herbs to give careful study to their proper selection. A number of herbs in common use today have toxic properties that the herbalist should be aware of. Some deaths from herbs have been reported.

Ginseng is one of the most common herbs currently used. It has been used for thousands of years by the Orientals as a stimulant and tonic. Those who advocate its use claim that it helps the body adapt to stress, corrects thyroid and adrenal malfunction, stimulates the nervous system and produces a sense of well-being and even euphoria.

Ginseng contains a number of pharmacologically active ingredients, mainly toxic glycosides. It contains small amounts of estrogens, which may cause swollen and painful breasts. When taken for as short a time as two weeks, ginseng can cause diarrhea, insomnia, and skin eruptions. Longer periods of use may induce high blood pressure, nervousness, cessation of menstruation in women, fluid retention, and in some people depression.

Lobelia is recommended as an expectorant, emetic, anti-asthmatic, and stimulant. Members of this family contain over a dozen alkaloids of high toxicity, including lobeline, which causes sweating, vomiting, low temperature, paralysis, rapid heart rate, and may produce coma and death.

Comfrey has been shown to contain alkaloids, which are highly toxic to the liver. As little as 0.5% of comfrey leaves in the diet of rodents produced both liver and bladder cancer. We no longer recommend the internal use of comfrey, but it may be used occasionally as an externally applied poultice. A study published in South Africa in 1979, suggests that comfrey may contain a substance toxic to the heart. Both the heart rate and the strength of the contraction were reduced in proportion to the strength of the dosage of comfrey administered.

Pennyroyal oil has been used to induce menstruation and abortion. It contains ketone pulegone, which is toxic to the liver and kidneys and may cause death. As little as one teaspoonful can cause seizures.

Sassafras root bark contains safrole, which is carcinogenic in animals and toxic to the liver.

Juniper berries, often recommended as a diuretic, are irritating to the gastrointestinal tract, and Juniper oil has an injurious effect on the kidneys. Horsetail contains thiaminase and nicotine, which produce excitement, diarrhea, difficult respirations, convulsions, and even coma and death. Recently introduced from South Africa, devil's claw root stimulates contraction of the uterine smooth muscle and should not be used during pregnancy. Mistletoe berries, leaves, and stems contain toxic substances, which may cause gastroenteritis, anemia, liver or intestinal hemorrhage, fatty degeneration of the thymus, depolarization of skeletal tissue, contracture of smooth muscle, shock, vasoconstriction, and cardiac arrest.

The seeds, leaves, and bark of many plants contain a cyanogenetic glycoside, amygdalin, which liberates hydrogen cyanide. Eating large amounts of these substances, or small amounts for long periods can result in cyanide poisoning or mutagenesis in cells leading to possible birth defects or cancer. Amygdalin is found in seeds of apricots, bitter almonds, cassava, cherries, choke cherries, peaches, pears, apples, and plums. The symptoms of poisoning are goiter, loss of ability to walk steadily, and blurring of vision leading sometimes to blindness. Apparently a fairly large quantity of the food item is needed to produce toxic symptoms. Nevertheless, even small amounts of cyanide exert an effect to inhibit respiratory enzymes at a cellular level. In minute quantities no ill effects can be sensed.

It seems unlikely that the use of most herbs to make teas as ordinarily brewed and used for an occasional illness could be dangerous to the health. Therefore we recommend that the medicinal herbs be taken as teas, not as capsules or tablets, and that the tea leaves or powder be steeped for only 15 minutes—never boiled or allowed to stand a long time on the leaves before straining. For use as a beverage, bear in mind that water cleanses the blood better than any other fluid. If a mild flavor is desired, twist a thin lemon round or crush a couple of mint leaves into your water.

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