Herbs & Supplements:
Astragalus
Astragalus membranaceus

Principal Proposed Uses
  • Strengthen Immunity (Against Colds, Flus, and Other Illnesses)
Other Proposed Uses
  • Atherosclerosis, Hyperthyroidism, Hypertension (High Blood Pressure), Insomnia, Diabetes, Chronic Active Hepatitis, Genital Herpes, AIDS, Chemotherapy Side Effects

Dried and sliced thin, the root of the astragalus plant is a common component of traditional Chinese herbal formulas. According to Chinese medical theory, astragalus "strengthens the spleen, blood and Qi, raises the yang Qi of the spleen and stomach, and stabilizes the exterior."¹ Don't worry if you didn't understand what you just read, because without many months of training in the unique Chinese approach to illness, there's no way you could have. Suffice it to say that the traditional understanding of the way astragalus works is different from the way it tends to be presented today.

What Is Astragalus Used for Today?

In the United States, astragalus has been presented as an immune stimulant useful for treating colds and flus. Many people have come to believe that they should take astragalus, like echinacea, at the first sign of a cold.

The belief that astragalus can strengthen immunity has a partial basis in Chinese tradition. The expression noted above, "stabilize the exterior," means helping to create a "defensive shield" against infection. However, according to Chinese healing tradition, astragalus formulas should not be taken during the early stage of infections. To do so is said to resemble "locking the chicken-coop with the fox inside," causing the infection to be "driven deeper." Rather, astragalus is supposedly only appropriate for use while you're healthy, for the purpose of preventing future illnesses. Since it was the Chinese who first developed astragalus, perhaps these traditions should be taken seriously.

What Is the Scientific Evidence for Astragalus?

Although Chinese herbal tradition suggests that astragalus should generally be used in combination with other herbs, modern Chinese investigators have found various intriguing effects when astragalus is taken by itself. Extracts of astragalus have been found to stimulate parts of the immune system in mice and humans, and to increase the survival time of mice infected with various diseases.^2,3 Other highly preliminary research suggests that astragalus might be useful in treating atherosclerosis, hyperthyroidism, hypertension, insomnia, diabetes, chronic active hepatitis, genital herpes, AIDS, and the side effects of cancer chemotherapy.^4–9 However, none of these possibilities can be regarded as proven.

Dosage

A typical daily dosage of astragalus involves boiling 9 to 30 g of dried root to make tea. Newer products use an alcohol-and-water extraction method to produce an extract standardized to astragaloside content, although there is no consensus on the proper percentage.

Safety Issues

Astragalus appears to be relatively nontoxic. High one-time doses, as well as long-term administration, have not caused significant harmful effects.¹⁰ Side effects are rare and generally limited to the usual mild gastrointestinal distress or allergic reactions. However, some Chinese herb manuals suggest that astragalus at 15 g or lower per day can raise blood pressure, while doses above 30 g may lower blood pressure.

As mentioned above, traditional Chinese medicine warns against using astragalus in cases of acute infections. Other traditional contraindications include "deficient yin patterns with heat signs" and "exterior excess heat patterns." Because understanding what these mean would require an extensive education in Chinese medicine, we recommend using astragalus only under the supervision of a qualified Chinese herbalist.

Safety in young children, pregnant or nursing women, or those with severe liver or kidney disease has not been established.

Last reviewed March 2002 by Medical Review Board

Back to Top