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Herbal Medicine

By Steven Novella, MD, Assistant Professor of Neurology, Yale University School of Medicine

Herbal medicine or herbalism, the oldest known form of health care, uses plants and plant extracts to treat disease and promote wellness. Either a single herb or a mixture of different herbs can be used. Chinese herbal medicine mixtures can also contain minerals and animal parts. Unlike conventional drugs, in which a single, active chemical may be extracted and isolated, herbal medicine usually makes use of the medicinal plant in its whole form.

Common herbal remedies include the following:

Herbal medicines (medicinal herbs) are available as extracts (solutions obtained by steeping or soaking a substance, usually in water), tinctures (usually alcohol-based preparations, with the alcohol acting as a natural preservative), infusions (the most common method of internal herbal preparation, usually referred to as a tea), decoctions (similar to an infusion), pills, powders, and injectables. Some herbal medicines are spread on a moistened cloth and applied to the skin.

Potential problems of medicinal herbs include the following:

  • Impurities: In the United States, the government has very little oversight of herbal products and places few regulations on the industry (see Overview of Medicinal Herbs and Nutraceuticals : Safety and Effectiveness). In contrast, in the European Union and Australia, government agencies regulate plant medicines as drugs.

  • Interactions: Some herbal medicines interact with drugs (for example, ginseng causes bleeding when used with warfarin—see Table: Some Possible Medicinal Herb–Drug Interactions) or foods (for example, St. John’s wort causes dangerously high blood pressure when consumed with aged cheeses, Chianti wine, or other foods high in tyramine).

  • Side effects: Some herbal medicines have side effects that can be harmful to certain people. For example, garlic reduces blood clotting and thus could increase the risk of bleeding in people taking anticoagulants (drugs that make blood less likely to clot). Garlic also increases blood sugar. Ginseng increases blood pressure.

People should tell their doctors all of the herbal medicines that they take.

More and more studies of medicinal herbs are being done. Some studies indicate that evidence for health claims is lacking. For example, a large well-designed study of ginkgo biloba found that ginkgo did not improve memory or prevent dementia in older people.

Did You Know...

  • There are many possible, potentially serious interactions between medicinal herbs and drugs or foods.

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