Astragalus

Astragalus is a vast genus in Fabaceae, the pea and bean family, and the name of the medicinal species is a source of confusion. Huang qi is traditionally described as the dried root of Astragalus membranaceus or Astragalus membranaceus var. mongholicus; Cochrane’s 2014 kidney review uses both names, and MSKCC lists both. Plants of the World Online, Kew’s global checklist, now accepts Astragalus mongholicus Bunge, published in 1868, as the correct name for the species and treats A. membranaceus var. mongholicus and A. membranaceus Fisch. ex Bunge as synonyms. NCBI Taxonomy files A. mongholicus as taxon 119829 and lists the variety name as a synonym, while still keeping a separate entry for A. membranaceus. In practice, research labelled with any of these names usually concerns the same medicinal root, but labels and papers will continue to use the older names for years.

Flora of China describes A. mongholicus as a perennial herb 25–60 cm tall with pinnate leaves 6–15 cm long, each carrying 8–12 pairs of small oval leaflets. Loose spikes of yellow, rarely lilac, pea flowers with a standard petal 13–20 mm long are followed by inflated, papery pods 2–3 cm long hanging on slender stalks. It grows on steppes, meadows, shrubby slopes, and in coniferous forest at 800–2,000 m across northern and western China, and Plants of the World Online gives its native range as Siberia to the Russian Far East, Mongolia, Korea, and northern and western China. Wang and colleagues report that plants flower in June to August, that good-quality roots are harvested after four to five years, and that the name huang qi refers to the root’s yellow colour and its standing as a leading tonic. The part used is the long, fibrous root, sold dried and cut into pale yellow slices.

More than 200 compounds have been isolated from astragalus root (Wang). The main groups are triterpenoid saponins called astragalosides, polysaccharides (more than 30 types have been described), and flavonoids, of which isoflavones such as formononetin and calycosin make up about 80%. Astragaloside IV (PubChem CID 13943297) and a calycosin glucoside are used as quality markers in the Chinese Pharmacopoeia. Cycloastragenol (CID 13943286, C30H50O5) is the aglycone of astragaloside IV, the saponin with its sugars removed, and is the basis of telomerase-activator supplements. The genus also has a dark side: Stegelmeier and colleagues (Journal of Natural Toxins 1999) describe locoweed poisoning, a chronic disease in livestock grazing certain Astragalus and Oxytropis species that contain swainsonine. The toxin blocks cellular mannosidases and causes a storage disease with neurological signs, some of them permanent. Medicinal huang qi is not a locoweed, but the genus is too large and varied to identify by eye.

Astragalus belongs to the oldest layer of Chinese herbal medicine. Wang and colleagues trace it to the Shennong Ben Cao Jing, compiled during the Han dynasty, where it was ranked as a superior herb. Zhang Zhongjing’s Golden Chamber (Jin Gui Yao Lue), from the late Eastern Han around AD 200, includes it in eight formulas, among them Huangqi Guizhi Wuwu Tang. Li Shizhen’s Compendium of Materia Medica, completed in the Ming dynasty in the sixteenth century, placed huang qi first among the tonic herbs. Later physicians leaned on it heavily: Li Dongyuan used it repeatedly as a tonic for the spleen and stomach in the thirteenth century, and in Wang Qingren’s Yi Lin Gai Cuo (1830) it is the most abundant ingredient in 11 of 33 prescriptions.

In traditional Chinese medicine terms, astragalus tonifies qi, the body’s vital energy, and is said to secure the exterior, meaning it strengthens the body’s surface against sweating and outside influences. It is also used to promote urination, reduce swelling, and help chronic sores heal (Wang). It is rarely given alone. Classic formulas include Bu Zhong Yi Qi Tang, with ginseng and other herbs, used for digestive weakness and organ prolapse; Danggui Buxue Tang, astragalus with dong quai, for deficiency of both qi and blood; and Yu Ping Feng San, astragalus with two other herbs, a traditional formula for colds, night sweats, and allergic rhinitis. The root is stir-baked with an adjuvant when a tonic effect is wanted and used raw to secure the exterior and promote urination (Wang).

Western interest grew from laboratory work on the immune system. MSKCC cites a 1988 study in which fractionated astragalus reversed immune suppression caused by the chemotherapy drug cyclophosphamide. Astragalus is now widely sold in the US and Europe as a supplement for immunity and fatigue, often in combination products. In China, an injectable form known as Huangqi injection is a patent medicine used for chronic heart failure, tested in dozens of Chinese trials (Fu, PLoS One 2011). In 2000 a small molecule that activates telomerase was identified by screening extracts of traditional Chinese medicines; Bernardes de Jesus and colleagues (Aging Cell 2011) describe this compound, TA-65, as purified from astragalus root. Harley and colleagues (Rejuvenation Research 2011) report that a commercial anti-ageing programme built around TA-65 was launched in 2007, yet the first blinded, placebo-controlled human trial was not published until 2016 (Salvador).

MSKCC attributes most of astragalus’s activity to its polysaccharides, saponins, and flavonoids, which in laboratory studies have immune-modulating, antioxidant, and anti-inflammatory effects. Astragalus polysaccharides activate macrophages through toll-like receptor 4 and enhance natural killer cell and monocyte activity in vitro. In healthy volunteers, an astragalus root extract raised counts of monocytes, neutrophils, lymphocytes, and platelets and increased circulating cytokines, and some people developed fatigue, malaise, and headache resembling a mild viral illness (MSKCC). That immune activation is the reason for caution in autoimmune disease and with immunosuppressant drugs. Formononetin has oestrogen-receptor effects in laboratory studies, and astragalus constituents, including astragaloside IV, show anticoagulant and clot-dissolving activity in the laboratory; whether either matters in people is unknown.

Astragalus has a diuretic reputation, and one human study supports it. Ai and colleagues (Journal of Ethnopharmacology 2008) gave 12 healthy men a single dose of aqueous astragalus extract (0.3 g per kilogram of body weight) and measured their urine. The extract markedly increased sodium excretion over the first four hours, apparently by enhancing the kidney’s response to atrial natriuretic peptide, and astragaloside IV was not the active component. MSKCC cites this as the basis for possible additive effects with diuretics, and Merck Manual separately warns that astragalus may reduce the excretion of lithium.

The telomere story concerns isolated compounds rather than the root. Telomeres are protective caps on chromosomes that shorten as cells divide, and the enzyme telomerase can rebuild them. In mice, TA-65 lengthened critically short telomeres through telomerase and improved some markers of health without significantly increasing overall cancer incidence (Bernardes de Jesus, Aging Cell 2011); a co-author, Calvin Harley, is disclosed as a consultant to the manufacturer in the later human trial. In drug-metabolism terms, MSKCC notes laboratory evidence that astragalus polysaccharides inhibit the P-glycoprotein drug pump, and LiverTox notes possible effects on cytochrome P450 enzymes, both of uncertain clinical relevance.

Chronic kidney disease is the best-reviewed use. Zhang and colleagues (Cochrane 2014) included 22 randomized or quasi-randomized studies with 1,323 participants, 241 of them on dialysis, in which astragalus was added to conventional treatment. No study reported the outcomes that matter most, time to dialysis or death. Astragalus reduced 24-hour protein in the urine (by 0.53 g in 10 studies), raised haemoglobin (by about 9.5 g per litre) and serum albumin, and improved creatinine clearance and serum creatinine. The studies were of low quality, and the reviewers concluded that definitive conclusions could not be made. NCCIH describes a 2023 review of 50 studies with 3,423 participants in membranous nephropathy, a kidney disorder, which found improvements in some kidney indicators but cited low quality, small size, and limited geographical range.

Cancer and chemotherapy: McCulloch and colleagues (Journal of Clinical Oncology 2006) pooled 34 randomized studies with 2,815 patients with advanced non-small-cell lung cancer receiving platinum-based chemotherapy with or without astragalus-based Chinese herbal medicine. In 12 studies with 940 patients, the herbal combinations were associated with a lower risk of death at 12 months (risk ratio 0.67) and better tumour response, but the authors stressed that the results needed confirmation in rigorously controlled trials. Taixiang and colleagues (Cochrane 2005) found four low-quality trials of huang qi decoctions given with chemotherapy for colorectal cancer, with less nausea and vomiting and fewer low white cell counts, but no robust demonstration of benefit. MSKCC notes that most studies in this field have poor methodology and that many used injectable astragalus, whose effects may not apply to oral products.

Heart failure: Fu and colleagues (PLoS One 2011) systematically reviewed Huangqi injection for chronic heart failure and found 62 trials, all conducted in China and published in Chinese journals. Their quality was so low, with inclusion criteria often unspecified and only one trial following patients for an adequate period, that the reviewers declined to pool the results. A 2024 meta-analysis by Han and colleagues (Frontiers in Pharmacology) of 19 trials with 1,565 patients with reduced ejection fraction reported that astragalus added to conventional therapy improved ejection fraction by about 6 percentage points and six-minute walking distance by about 68 m, again noting the limited quality of the studies. These outcomes are heart scans, blood markers, and walking tests rather than deaths or hospital admissions.

Colds and immunity: the traditional use of astragalus to ward off colds has almost no rigorous testing. Su and colleagues (Cochrane 2016) screened 6,080 records for placebo-controlled trials of oral astragalus alone to prevent frequent respiratory infections in children and found none; 44 otherwise eligible studies lacked a placebo group. NCCIH describes a 2023 review of 19 small, heterogeneous studies with 1,094 participants suggesting enhanced immune responses, which is not the same as fewer infections. In a placebo-controlled trial in 48 adults with seasonal allergic rhinitis, a supplement containing astragalus reduced runny nose more than placebo but did not improve the other main symptom measures (Matkovic, Phytotherapy Research 2010).

Other claims: NCCIH reports a 2024 review of 20 studies with 953 adults with type 2 diabetes in which astragalus added to metformin lowered fasting glucose and HbA1c more than metformin alone, but most studies were of low quality with risk of bias. For telomeres, Salvador and colleagues (Rejuvenation Research 2016) randomized 117 cytomegalovirus-positive adults aged 53–87 to two doses of TA-65 or placebo for a year. Telomere length rose by 530 base pairs on the low dose and fell by 290 on placebo, while the high dose showed no significant change. The study was funded by the manufacturer, TA Sciences, two authors were employees and three were consultants, and telomere length is a laboratory marker, not evidence of longer or healthier life.

There is no EU herbal monograph for astragalus, and no regulator has set a recommended dose. In traditional Chinese practice, Wang and colleagues cite the Dictionary of Traditional Chinese Medicine for 9–15 g of dried root a day as a decoction, with larger doses of 30–60 g. The root is simmered in water, usually alongside other herbs in a formula chosen by a practitioner; stir-baked root is preferred for tonifying and raw root for securing the exterior, promoting urination, and treating sores. NCCIH says that oral doses of up to 60 g a day for up to four months do not seem to cause adverse effects, but that a thorough safety evaluation has not been done.

Western products include capsules of powdered root, liquid extracts and tinctures, and dry extracts standardized to astragalosides, often astragaloside IV. Many astragalus supplements are multi-ingredient blends, and LiverTox points out that the purity and potency of commercial preparations are not rigorously regulated. TA-65 is a proprietary product sold for telomere support rather than a traditional root preparation, and cycloastragenol is sold separately as a dietary ingredient. Huangqi injection is a hospital medicine in China; trial results for injections should not be assumed to apply to capsules or teas.

Choose a product that names the species and the plant part (root) and comes from a manufacturer that tests identity and contaminants. Do not dig or forage wild astragalus or milkvetch: some members of the genus accumulate swainsonine or other toxins and are hard to tell apart. If you take any prescription medicine, particularly an immunosuppressant, lithium, diabetes or blood pressure treatment, or a blood thinner, discuss astragalus with your doctor or pharmacist before starting it, and tell your cancer team about any herbs during treatment.