Astragalus, a plant with the poetic name Huang Qi, meaning “yellow energy” in Chinese, has been a cornerstone of traditional Asian medicine for centuries. But beyond ancestral traditions, what does modern science really say about this revered root? Laboratories around the world have been studying its immunostimulating properties for several decades, and the results are proving particularly promising.
Polysaccharides that stimulate immune cells
The key to astragalus’s immune properties lies in its polysaccharides, the long chains of complex sugars that constitute its major active ingredients. A systematic review published in Archives of Pharmacal Research in 2022 compiled all the research on the subject. Researchers demonstrated that astragalus polysaccharides directly activate several types of immune cells: macrophages, natural killer cells, dendritic cells, T lymphocytes, and B lymphocytes. A study published in the journal Molecules in 2012 precisely analyzed the mechanism of action. Scientists have discovered that astragalus extract increases heparanase activity in macrophages, an enzyme that facilitates cell migration and the release of immune mediators such as interleukin-1 beta and tumor necrosis factor alpha. These chemical messengers mobilize the entire immune system to fight off attacks.
A measurable effect on T lymphocytes
The impact of astragalus on T lymphocytes, the frontline soldiers of our immune system, has been the subject of extensive investigation. A meta-analysis published in 2023 in Complementary Medicine Research combined 19 clinical studies involving 1,094 human participants. The results confirm that astragalus significantly increases CD3 cell levels and improves the CD4/CD8 ratio, two essential markers of immune function.
More specifically, a randomized controlled trial conducted on the Polish national rowing team in 2021 evaluated the effects of astragalus supplementation during intensive training. Researchers administered 500 milligrams of astragalus root extract daily for six weeks to ten athletes, compared to eight receiving a placebo. The results, published in the Journal of the International Society of Sports Nutrition, show that the supplemented group maintains a better balance of regulatory and cytotoxic T lymphocytes after exercise, whereas the placebo group experiences a marked decline.
Protection during chemotherapy
One of the best-documented applications of astragalus concerns its protective role during cancer treatments. A Chinese clinical study involving 120 patients with malignant tumors revealed that the intravenous administration of astragalus in addition to chemotherapy significantly limits the drop in white blood cells and platelets, major side effects of these harsh treatments.
Research published in The American Journal of Chinese Medicine in 2016 details how astragalus polysaccharides and saponins modulate cancer signaling pathways while boosting immunity. Scientists observed that astragalus reduces toxicity induced by immunosuppressant drugs and chemotherapy agents, allowing patients to better tolerate their treatments.
Another study on mice with lung tumors showed that combining astragalus polysaccharides with other compounds drastically improves thymic index, splenic index, and the CD4/CD8 ratio, increasing levels of anti-tumor cytokines such as interferon-gamma and interleukin-2.
An inflammation modulator
Astragalus not only stimulates the immune system, but also intelligently regulates it. A study published in the International Journal of Molecular Sciences in 2012 demonstrated that astragalus inhibits inflammation via the phospho-P38 MAPK and NF-κB pathways in stimulated macrophages. This regulatory action prevents runaway inflammation while maintaining an effective immune response.
Work conducted on septic mice and published in 2015 in Evidence-Based Complementary and Alternative Medicine revealed that astragalus polysaccharides maintain helper and regulatory T cell populations in the spleen and intestinal Peyer’s patches, crucial areas of immunity. Researchers noted improved cell activation at doses of 200 and 400 milligrams per kilogram of body weight.
Results on asthma and allergies
Astragalus also shows promising effects on chronic inflammatory conditions. A study published in Biochemistry and Biophysics Reports in 2014 used a mouse model of ovalbumin-induced asthma. Scientists found that administering astragalus reduced serum IgE levels, decreased eosinophil count, and reduced inflammatory cell infiltration in the lungs. Th2 cytokine RNA and protein levels also decreased, while astragalus activated the PPARγ receptor, which is involved in immune regulation.
More recently, a February 2025 study published in Preventive Nutrition and Food Science examined the effects of astragalus leaf extract on allergic reactions in immune cell lines. The results show a suppression of histamine and leukotriene B4 release by stimulated mast cells, as well as a reduction in nitric oxide and pro-inflammatory cytokines in macrophages.
Activation of Dendritic Cells
Dendritic cells act as sentinels, capturing antigens and presenting them to T lymphocytes to trigger the immune response. Several studies demonstrate that astragalus polysaccharides accelerate the maturation of these key cells. In mouse models receiving a DNA vaccine against hepatitis B, astragalus used as an adjuvant at a dose of 500 micrograms per mouse significantly increased the expression of MHC I, MHC II, CD40, CD80, and CD86 molecules on the surface of dendritic cells.
These maturation markers indicate that dendritic cells become more efficient at presenting antigens and activating cytotoxic T lymphocytes, thus strengthening the adaptive immune response.
- Dosage and practical considerations
- Most clinical studies use doses ranging from 250 to 500 milligrams of standardized astragalus extract per day. The Polish study on rowers showed beneficial effects with 500 milligrams daily for six weeks. Other research uses higher doses, up to several grams per day in traditional decoction, without notable side effects. Astragalus has an excellent safety profile. No significant toxicity has been reported in the scientific literature at the recommended doses. Animal studies using very high doses have not revealed any major adverse effects. However, as with any medicinal plant, caution is still advised during pregnancy and breastfeeding, although data are lacking to establish formal contraindications.
- Perspectives and limitations
- Despite encouraging results, research on astragalus has limitations. Many studies originate from China and sometimes exhibit methodological biases. The standardization of extracts varies considerably between commercial products, making comparisons difficult. Meta-analyses reveal substantial heterogeneity between studies, suggesting the need for more rigorous research.
- Nevertheless, the convergence of results across dozens of preclinical and clinical studies paints a coherent picture. Astragalus acts as a potent immunomodulator, stimulating the immune system when it is weakened and regulating it when it is overactive. This balancing action fully justifies its status as an adaptogenic plant in traditional medicine. Modern science thus validates what Chinese physicians have empirically observed for two millennia: Huang Qi truly strengthens the body’s defensive energy, not magically, but through precise and measurable immunological mechanisms.
- Cited scientific sources:
- Li CX, et al. (2022). Astragalus polysaccharide: a review of its immunomodulatory effect. Archives of Pharmacal Research, 45(6):367-389.
- https://pubmed.ncbi.nlm.nih.gov/35713852/ Liu Y, et al. (2012). Astragalus membranaceus Extract Activates Immune Response in Macrophages via Heparanase. Molecules, 17(6):7232-7240.
