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Astragalus(Astragalus membranaceous)rating:
The astragalus species that is obtained from China is A. membranaceous, also known as Mongolian milk vetch, or by its Chinese name, huang qi. It is quite different from other species of Astragalus, known as locoweeds, which contain large amounts of selenium and other potential toxins, and from the Middle Eastern plant, A. gummifer, which is the source of gum tragacanth.
Uses and Benefits:
In Chinese traditional medicine, the root of A. membranaceous is a popular and potent tonic used for numerous specific indications, especially infections. It is thought to improve depressed immunity, and therefore it has been recommended for the treatment of AIDS and other viral diseases, and as an adjuvant in cancer therapy. The herb is now advocated for a wide variety of illnesses, including the common cold, influenza, respiratory insufficiency, diabetes, hypertension, liver disease, cardiac ischemia, heart failure, vascular insufficiency, and nephritis.
Pharmacology:
The important constituents include numerous triterpene saponins, known as astragalosides and related compounds such as soyasaponins. A number of polysaccharides, such as astragalans I-IV, have been isolated. Important flavonoids include quercetin and kaempferol; among its many other constituents are isoflavonoids, sugars, amino acids, and linoleic acid. It is unclear which of the numerous constituents are of therapeutic value. However, the polysaccharides and saponins have been suggested to be the major agents.
The polysaccharide fractions of the root extract have been reported to have in vitro effects that suggest an immune-enhancing capability. There is some evidence that astragalus can potentiate the effect of interferon against viruses and can increase IgA and IgM in nasal secretions in humans. Animal experiments have shown that extracts of astragalus can restore the immune properties of cancer patient T-cells in vitro. A more recent rat study does not confirm earlier reports that astragalus extract can prevent myelosuppression by cyclophosphamide.
Clinical Trials:
Almost all of the clinical studies on astragalus are in Chinese medical books or journals and are therefore not readily evaluated. In an open study on 1000 subjects, 8 it is alleged that a 2-month prophylactic course of the herb in a dosage of 8 g/day in combination with interferon was correlated with a significant reduction in colds compared to placebo or interferon alone. Benefits in humans for a wide variety of chronic and serious disorders also have been reported. For example, it is asserted that astragalus increases serum IgM, IgE, and cAMP; enhances left ventricular function and cardiac output in patients with angina pectoris; improves hemorrhagic indices in patients with systemic lupus erythematosus; increases survival in lung cancer when combined with conventional therapy; improves leukopenia; improves liver function in chronic viral hepatitis; and so on
However, none of these reports are evaluable, and the testing applied as well as the observations made by investigators do not conform to standard methods used in Western medicine. In general, these studies were uncontrolled or unblinded, and no reliable clinical studies in support of these indications have been reported in the English-language peer-reviewed literature. Thus, there is only very equivocal evidence to support the numerous clinical claims that are made for astragalus, particularly as an immune system restorative or as an immune modulator for use in the treatment of cancer.
Adverse Effects:
Herbalists regard astragalus as very safe based on its reputation as a valued traditional medication. It is unlikely that astragalus has any serious toxicity, although there is a lack of reliable clinical data.
Side Effects and Interactions:
There are no recognized drug interactions.
Cautions:
Astragalus can be obtained in combination mixtures, in which other agents may have a potential for toxicity.
Preparations & Doses:
Sliced astragalus root is often used to make teas, soups, or decoctions. The usual daily dose varies from 2 to 30 g or more of the dried root; although large doses appear to be safe, 8-15 g/day seems to be more reasonable. Some products contain standardized extracts, packaged in unit doses. Capsules containing 150-500 mg are commonly marketed, to be taken as often as 8 or 9 times a day; tinctures and fluid extracts are also available. In traditional Chinese medicine, it is usual to take astragalus in combination with other herbs.
Summary Evaluation
A membranaceous is a popular Chinese herb that has long been used as a tonic. Increasing claims suggest that it is of value as an immune restorative to fight viral diseases, as a treatment for Lancer, and as a cure for other disorders. However, the scientific evidence of clinical effectiveness is of unclear quality, and has not been validated outside the Asian literature. Thus, actual benefits are not substantiated. The fact that large doses can be taken with reported toxicity suggests that astragalus has minimal pharmacologic potency.
