What is astragalus?
Astragalus is a perennial plant that is native to China, Mongolia, and Korea.
Advocates believe that astragalus is an adaptogen Adaptogens "Adaptogen" is a term for certain foods and supplements that are said to help the body cope with "stress." Stress may be psychologic (in the mind), but also may be physical (in the body), and... read more . This herbal medicine term means that this substance is thought to help the body respond to stress and restore normal function. In 2020 and 2021, many people have used astragalus to diminish the harmful effects of COVID-19 infection, although there is no evidence to support that use.
The roots of the astragalus plant have been used for centuries in combination with other herbs as part of traditional Chinese medicine Traditional Chinese Medicine (TCM) Originating in China several millennia ago, traditional Chinese medicine is based on the theory that illness results from the imbalance of the life force (qi, pronounced chee) through the body... read more .
Of the more than 2,000 species of astragalus, just 2 are typically used in dietary supplements: Astragalus membranaceus and Astragalus mongholicus.
Other names for astragalus include huáng qí and milkvetch.
Astragalus is available in liquid extracts, capsules, powders, and teas.
Astragalus contains antioxidants, which can potentially prevent cell damage.
What claims are made about astragalus?
The long list of health benefits claimed for this herb includes the following:
Boosts the immune system (although what this means or how this could be done is not clear)
Lowers blood pressure
Protects the liver and kidneys
Prevents and treats heart disease
Reduces nausea and vomiting caused by chemotherapy
Lowers blood sugar levels in people with diabetes
Prevents colds and other upper respiratory tract infections
Does astragalus work?
Any single compound, including astragalus, is highly unlikely to have such a broad range of health benefits. Thus, evidence is very unlikely to confirm such multiple benefits.
The evidence from studies in people to show that astragalus has the claimed health benefits is limited. Most or all of these studies are small (fewer than 150 participants) and of poor quality. These studies suggest that astragalus, often combined with standard treatment, could have the following benefits, among others:
Improve heart function in people with heart failure Heart Failure (HF) Heart failure is a disorder in which the heart is unable to keep up with the demands of the body, leading to reduced blood flow, back-up (congestion) of blood in the veins and lungs, and/or... read more who are also treated with standard therapy (although some evidence does not confirm this benefit)
Reduce signs of kidney damage in people with chronic kidney disease Chronic Kidney Disease Chronic kidney disease is a slowly progressive (months to years) decline in the kidneys’ ability to filter metabolic waste products from the blood. Major causes are diabetes and high blood pressure... read more
Injectable forms of astragalus might reduce symptoms and improve quality of life in people with cancer, but evidence is lacking to show that oral forms of the root offer the same benefits.
Larger, well-designed, and longer studies are needed to confirm any benefits of astragalus.
What are the possible side effects of astragalus?
Most people tolerate astragalus well. But in rare cases, people in astragalus studies have developed minor side effects, including rashes, headache, fatigue, itching, runny nose, nausea, and diarrhea. Some astragalus species that are not included in commercial supplements may be toxic because they contain "swainsonine," an ingredient that is toxic to the nervous system. In animals, this ingredient has caused "locoweed" poisoning.
Taking up to 60 grams (about 2 ounces) of astragalus per day for up to 4 months seems to be safe for most people. But studies have not assessed the safety of taking higher doses or taking astragalus supplements for longer than 4 months. (In general, unlike with prescription drugs, there is little evidence about the best dose of supplements.)
Not enough research has been done on the use of astragalus by pregnant and breastfeeding women or by children to tell whether this herb is safe for these groups.
If, as claimed, astragalus increases activity of the immune system Overview of the Immune System The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include Microorganisms (commonly called germs, such as bacteria, viruses, and fungi) Parasites... read more , this could be a problem for people with an autoimmune disease Autoimmune Disorders An autoimmune disorder is a malfunction of the body's immune system that causes the body to attack its own tissues. What triggers an autoimmune disorder is not known. Symptoms vary depending... read more , such as lupus, rheumatoid arthritis, or multiple sclerosis.
What drug interactions occur with astragalus?
Because astragalus can make the immune system more active, it might reduce the effects of drugs (such as tacrolimus and cyclosporine) that suppress immune system activity.
Astragalus and its components have similar effects to the hormone estrogen, so it could decrease effectiveness of cancer treatments designed to suppress estrogen.
Astragalus seems to prevent blood from clotting, so it could increase the risk of bleeding in people taking anticoagulants.
Astragalus might lower blood pressure too much in people taking drugs to lower their blood pressure.
Astragalus might increase the impact of diuretics (drugs to increase urine).
Astragalus might make it hard for the body to get rid of lithium, so dangerous levels of lithium could build up in people who take both astragalus and lithium.
No health benefits of astragalus have been confirmed in high-quality studies in people.
Use of astragalus is not recommended because there are no confirmed benefits to outweigh the possibility of negative side effects.
Astragalus seems to be safe for most people; however,
Pregnant women, children, people with autoimmune diseases, and those with liver disease should avoid astragalus.
Women who are breastfeeding and people who take certain drugs (including drugs to suppress the immune system, hormonal treatments, anticoagulants, blood pressure drugs, lithium, and diuretics) should talk to their doctor before taking astragalus.