Astragalus (Astragalus membranaceus, in the legume family) has been used in Chinese medicine for hundreds of years, usually combined with other herbs, to stimulate the immune system and treat respiratory infections, fatigue, loss of appetite, and many other ailments. Typically, what’s used is the plant’s root, which is available in capsules, liquid extracts, powders, and teas.
Herbalists call astragalus an “adaptogen,” meaning that it is supposed to help restore balance when the body is exposed to various physical and mental “stressors,” thereby boosting overall strength and vitality—a concept integral to Eastern medicine, but not scientifically backed or recognized by Western medicine. Perhaps the best-known adaptogen is ginseng, which is touted for general well-being.
Astragalus contains flavonoids, saponins, phytosterols, and other potentially beneficial compounds. Lab and some human studies have shown that it has antimicrobial, anti-inflammatory, antioxidant, anti-tumor, and immune-boosting effects. Not surprisingly then, scientists are interested in its potential benefits for heart disease, cancer, HIV infection, allergies, and other conditions.
The problem, as with most herbs, however, is that there are few well-designed clinical trials. Moreover, the studies, mostly done in China, mix astragalus with other herbs, so it’s impossible to know what is having an effect, if there is one.
A systematic review of 34 Chinese studies, by researchers here at UC Berkeley’s School of Public Health in 2006, found evidence that astragalus-based Chinese herbal formulas may improve tumor response and survival in people with lung cancer who are undergoing chemotherapy—but the studies are of poor quality and the benefits may have come from the other herbs. In a placebo-controlled study in Phytotherapy Research in 2010, allergy sufferers who took a supplement containing astragalus for six weeks reported some improvement in symptoms, but the study was small and the supplement also contained a “mineral complex.”
The government’s National Center for Complementary and Alternative Medicine says that astragalus might play a role in cancer treatment and benefit the heart, liver, and immune system. But according to the American Cancer Society, “the consensus of available scientific evidence does not support claims that astragalus can prevent or cure cancer in humans or decrease the toxic effects of chemotherapy or other conventional cancer treatments.” The Natural Standard, which evaluates alternative and complementary remedies, gives it a “C” across the board, meaning there is unclear or conflicting evidence for all purported medical uses.
Though generally deemed safe, astragalus may interact with some medications, including a number of immune-suppressive drugs and drugs that affect blood clotting. If the herb affects the immune system, that could perhaps be a problem for people with autoimmune diseases. Some side effects have also been reported: diarrhea, increased urination, and changes in blood sugar and blood pressure levels. It’s possible, too, that anyone allergic to legumes (beans, peas, lentils) could also have adverse reactions to astragalus.
Bottom line: Astragalus might one day prove to have benefits, particularly to the immune system, but large-scale studies are needed before we would recommend it. In the meantime, don’t believe claims that astragalus will “supercharge your cells,” cure AIDS, improve bone density, or increase your life expectancy.