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.
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.
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).
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.
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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.