Astragalus

Overview

Astragalus is an herb from traditional Chinese medicine (TCM) which is traditionally used for its immune enhancing properties, but is also recommended in TCM for "deficiency of chi" (life force) – which might include symptoms such as lack of energy and fatigue. Similar to Echinacea, astragalus exhibits immune-enhancing effects from the polysaccharides contained in the root. Modern medical practitioners have recently become involved in researching astragalus in reducing the side effects of chemotherapy, upper respiratory infections, promoting cardiovascular health, hepatoprotection, and male infertility.

Comments

Astragalus has been used as an herbal “tonic” for centuries in Traditional Chinese Medicine (TCM) and in Native American folk medicine. As a tonic, astragalus is used primarily as a “prevention” herb throughout the cold and flu season – a different usage than the more popular Echinacea, which is best used for early stage treatment as soon as you feel a cold or flu coming on. Most of what we know about astragalus, however, comes from test tube and animal experiments, which show that astragalus can help fight bacteria and viruses by enhancing various aspects of the body's normal immune response (enhanced function of specific immune system cells such as T cells, lymphocytes and neutrophils). In TCM, astragalus is often combined with other “tonic” herbs such as Ginseng, Cordyceps or Ashwagandha, to keep the immune system “humming” during periods of high stress.

The scientific evidence for the ability of astragalus to enhance the immune system and improve cardiovascular disease and cancer comes from human, animal, and in vitro studies. Some of these studies show significant beneficial results for astragalus. However, insufficient and unreliable data exists in the uses for this herb. Unless a patient has an autoimmune disease or is taking immune suppressant medications, this herb is an option for treatment and/or symptom relief in various conditions.

Scientific Support

The astragalus root is the part that contains the important saponin and polysaccharide constituents. These saponins have diuretic effects as well as anti-inflammatory and antihypertensive activity. Due to the various elements contained in the plant, (amino acids, coumarins, flavanoids, isoflavanoids, polysaccharides, and trace minerals), it is unclear which agents provide which activities.

Several chemical constituents of astragalus have been identified as potential active compounds, including saponins, flavonoids, polysaccharides and glycosides. Astragalus is often combined with other adaptogenic herbs, such as ginseng, and promoted as a guard against various internal and external stressors. Combination of astragalus with echinacea is common for protection against common infections of the mucous membranes (cold and flu).

Most of the scientific data on astragalus comes from Chinese clinical evidence, where astragalus appears to stimulate the immune system in patients with infections. At least one clinical trial in the U.S. has shown astragalus to boost T-cell levels close to normal in some cancer patients, suggesting the possibility of a synergistic effect of astragalus with chemotherapy. In animal studies, astragalus extracts have been shown effective in preventing infection of mice by influenza virus, possibly by increasing the phagocytotic activity of the white blood cells of the immune system.

In several Chinese studies (Duan et al. 2002, Zou et al. 2003) cancer patients have responded favorably to astragalus preparations (higher remission rate), probably owing to an inhibition of chemotherapy induced immune suppression (lesser decrease of white blood cell count and higher IgG and IgM levels). Numerous animal studies have indicated astragalus also possesses broad antioxidant and hepatoprotective effects, likely due to the presence of a variety of saponin and flavonoid compounds. As a general supporter of immune system function, astragalus has been studied in rodent models and in humans with a generally beneficial, if modest, effect on maintaining immune system function during chemotherapy and radiotherapy (Cha et al. 1994, Niu et al. 2001, Wu et al. 2001).

Safety/Dosage

When used as recommended, astragalus has no known side effects, but gastrointestinal distress and diarrhea are possible at high intakes. Astragalus is available as a single-ingredient supplement, but it may be even more effective in lower doses (100-200mg/day) when combined with other immune-stimulating herbs and nutrients. Approximately 500mg per day is recommended for stimulation of the immune system and to provide resistance to the effects of stress. Divided doses of 250mg per day of a standardized (for saponins and flavonoids) root extract are preferred. Use with caution in autoimmune disease due to the immunostimulating properties of astragalus. Consider discontinuing astragalus prior to surgery as astragalus may increase the risk of bleeding.

References

1.Cha RJ, Zeng DW, Chang QS. Non-surgical treatment of small cell lung cancer with chemo-radio-immunotherapy and traditional Chinese medicine. Zhonghua Nei Ke Za Zhi 1994; 462-6.

2.Chu DT, Lepe-Zuniga J, Wong WL, LaPushin R, Mavligit GM. Fractionated extract of Astragalus membranaceus, a Chinese medicinal herb, potentiates LAK cell cytotoxicity generated by a low dose of recombinant interleukin-2. J Clin Lab Immunol. 1988 Aug;26(4):183-7.

3.Chu DT, Wong WL, Mavligit GM. Immunotherapy with Chinese medicinal herbs. II. Reversal of cyclophosphamide-induced immune suppression by administration of fractionated Astragalus membranaceus in vivo. J Clin Lab Immunol. 1988 Mar;25(3):125-9.

4.Duan P, Wang ZM. Clinical study on effect of astragalus in efficacy enhancing and toxicity reducing of chemotherapy in patients of malignant tumor. Zhongguo Zhong Xi Yi Jie He Za Zhi 2002; 22: 515-7.

5.Li SQ, Yuan RX, Gao H. Clinical observation on the treatment of ischemic heart disease with astragalus membranaceus. Zhongguo Zhong Xi Yi Jie He Za Zhi 1995; 15: 77-80.

6.Liu ZG, Xiong ZM, Yu XY. Effect of astragalus injection on immune function in patients with congestive heart failure. Zhongguo Zhong Xi Yi Jie He Za Zhi 2003; 23: 351-3.

7.Luo HM, Dai RH, Li Y. Nuclear cardiology study on effective ingredients of Astragalus membranaceus in treating heart failure Zhongguo Zhong Xi Yi Jie He Za Zhi 1995; 15: 707-9.

8.Niu HR, Lai ZH, Yuan L. Observation on effect of supplementary treatments by astragalus injection in treating senile pulmonary tuberculosis patients. Zhongguo Zhong Xi Yi Jie He Za Zhi 2001; 21: 346-50.

9.Rittenhouse JR, Lui PD, Lau BH. Chinese medicinal herbs reverse macrophage suppression induced by urological tumors. J Urol. 1991 Aug;146(2):486-90.

10.Sinclair S. Chinese herbs: a clinical review of Astragalus, Ligusticum, and Schizandrae. Altern Med Rev. 1998 Oct;3(5):338-44.

11.Sun Y, Hersh EM, Talpaz M, Lee SL, Wong W, Loo TL, Mavligit GM. Immune restoration and/or augmentation of local graft versus host reaction by traditional Chinese medicinal herbs. Cancer. 1983 Jul 1;52(1):70-3.

12.Zhang JG, Gao DS, Wei GH. Clinical study on effect of Astragalus injection on left ventricular remodeling and left ventricular function in patients with acute myocardial infarction. Zhongguo Zhong Xi Yi Jie He Za Zhi 2002; 22: 346-8.

13.Zhang ZL, Wen QZ, Liu CX. Hepatoprotective effects of astragalus root. Journal of Ethnopharmacology 1990; 30: 146-49.

14.Zhao KS, Mancini C, Doria G. Enhancement of the immune response in mice by Astragalus membranaceus extracts. Immunopharmacology. 1990 Nov-Dec;20(3):225-33.

15.Zhou ZL, Yu P, Lin D. Study on effect of astragalus injection in treating congestive heart failure. Zhongguo Zhong Xi Yi Jie He Za Zhi 2001; 21: 747-9.

EDITOR'S NOTE: This monograph can be found in The Health Professional's Guide to Dietary Supplements (Lippincott, Williams & Wilkins) by Shawn M. Talbott, PhD and Kerry Hughes, MS.