Astragalus

• Immune system support
• Cardiovascular health
• Stress adaptation
• Anti-inflammatory effects
• Antioxidant protection

• Blood sugar regulation
• Kidney support
• Liver protection
• Energy enhancement
• Respiratory health
• Wound healing
• Telomere protection
• Potential anti-cancer effects
• Adrenal support
• Improved exercise recovery

Astragalus exerts its diverse biological effects through multiple mechanisms involving immune modulation, antioxidant activity, cardiovascular protection, and adaptogenic properties. These effects are attributed to its complex phytochemical composition, which includes polysaccharides, flavonoids, saponins, and various other bioactive compounds. The immunomodulatory effects of astragalus are primarily mediated by its polysaccharides, particularly astragalus polysaccharides (APS). These compounds enhance both innate and adaptive immunity through several pathways.

APS stimulates macrophage activity by increasing phagocytosis, enhancing nitric oxide (NO) production, and promoting the release of cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α). This activation of macrophages contributes to improved pathogen clearance and enhanced immune surveillance. Additionally, APS increases natural killer (NK) cell cytotoxicity, enhancing the body’s ability to eliminate virally infected and cancerous cells. Research has demonstrated that APS can increase NK cell activity by 20-45% in various experimental models.

In the adaptive immune system, astragalus influences T-cell function by promoting the proliferation and differentiation of T lymphocytes. It modulates the balance between T helper 1 (Th1) and T helper 2 (Th2) responses, which is crucial for appropriate immune reactions to different types of pathogens. Astragalus also enhances B-cell function and antibody production, contributing to humoral immunity. Studies have shown increased levels of immunoglobulins IgA, IgG, and IgM following astragalus administration.

The antioxidant properties of astragalus are attributed to both its flavonoid content and polysaccharides. Flavonoids such as calycosin, formononetin, and quercetin directly scavenge free radicals and reactive oxygen species (ROS). Additionally, astragalus upregulates endogenous antioxidant defense systems by enhancing the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). This dual approach to oxidative stress protection contributes to astragalus’s cell-protective effects and may underlie many of its health benefits.

Astragalus exhibits significant cardiovascular protective effects through multiple mechanisms. It improves endothelial function by increasing nitric oxide production and enhancing endothelial nitric oxide synthase (eNOS) activity, leading to vasodilation and improved blood flow. The herb also demonstrates anti-inflammatory effects on vascular tissues by inhibiting nuclear factor-kappa B (NF-κB) signaling and reducing the expression of adhesion molecules such as ICAM-1 and VCAM-1, which are involved in atherosclerotic plaque formation. Additionally, astragalus has been shown to reduce platelet aggregation and improve lipid profiles by decreasing total cholesterol and low-density lipoprotein (LDL) levels while increasing high-density lipoprotein (HDL) levels.

The adaptogenic properties of astragalus involve modulation of the hypothalamic-pituitary-adrenal (HPA) axis, which regulates stress responses. Astragalus appears to normalize cortisol levels and improve stress resilience by modulating glucocorticoid receptor sensitivity and function. This helps prevent the deleterious effects of chronic stress on immune function, cardiovascular health, and cognitive performance. In the context of kidney function, astragalus demonstrates nephroprotective effects by improving renal blood flow, reducing proteinuria, and protecting podocyte function.

These effects are mediated through anti-inflammatory actions, antioxidant protection, and modulation of transforming growth factor-beta (TGF-β) signaling, which is involved in renal fibrosis. Astragalus has also shown potential anti-aging effects, particularly through its impact on telomere biology. Astragaloside IV, a major saponin in astragalus, has been found to activate telomerase, the enzyme responsible for maintaining telomere length. Since telomere shortening is associated with cellular aging, this mechanism may contribute to astragalus’s traditional reputation as a longevity herb.

At the cellular level, astragalus influences various signaling pathways that regulate cell survival, proliferation, and metabolism. It activates the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) pathway, which promotes cell survival and growth. It also modulates the mammalian target of rapamycin (mTOR) pathway, which regulates protein synthesis and cellular metabolism. Additionally, astragalus affects the mitogen-activated protein kinase (MAPK) cascades, including the extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 pathways, which are involved in cellular responses to various stimuli.

The herb’s effects on glucose metabolism include enhanced insulin sensitivity through activation of the insulin receptor substrate-1 (IRS-1) and glucose transporter type 4 (GLUT4) translocation, leading to improved glucose uptake in peripheral tissues. This mechanism contributes to astragalus’s potential benefits in metabolic health and blood sugar regulation. The diverse mechanisms of action of astragalus reflect its complex phytochemical composition and explain its wide range of traditional uses and potential therapeutic applications. The herb’s ability to modulate multiple physiological systems simultaneously is characteristic of adaptogenic herbs and contributes to its holistic effects on health and resilience.

The bioavailability of astragalus compounds is complex and varies significantly depending on the specific bioactive constituents, extraction methods, formulation, and individual physiological factors. Understanding these variables is crucial for optimizing therapeutic outcomes. Astragalus contains three main classes of bioactive compounds—polysaccharides, flavonoids, and saponins—each with distinct bioavailability profiles. Astragalus polysaccharides (APS), which are responsible for many of the herb’s immunomodulatory effects, face significant challenges in oral bioavailability due to their high molecular weight (typically 10,000-1,000,000 Da) and hydrophilic nature.

These characteristics limit passive diffusion across the intestinal epithelium. Research suggests that APS absorption occurs primarily through three mechanisms: paracellular transport through tight junctions, endocytosis by enterocytes, and M-cell-mediated uptake in Peyer’s patches. Studies using radiolabeled APS have demonstrated that approximately 2-10% of orally administered polysaccharides are absorbed into systemic circulation, with the remainder either metabolized by gut microbiota or excreted. The flavonoid components of astragalus, including calycosin, formononetin, and quercetin derivatives, generally show moderate bioavailability.

These compounds undergo significant first-pass metabolism in the intestinal wall and liver, primarily through phase II conjugation reactions (glucuronidation and sulfation). Pharmacokinetic studies in rats have shown that the bioavailability of calycosin, a major astragalus flavonoid, is approximately 36% when administered as part of a complex extract, but only 11% when administered as an isolated compound, suggesting that other components in the whole herb extract may enhance flavonoid absorption. Astragaloside IV, the primary saponin in astragalus and a compound of significant research interest for its telomerase-activating and cardiovascular protective effects, demonstrates poor oral bioavailability (approximately 2.2% in rat models). This limited bioavailability is attributed to its large molecular size, poor water solubility, low membrane permeability, and susceptibility to hydrolysis in the gastrointestinal tract.

P-glycoprotein efflux in the intestinal epithelium further reduces its absorption. Several factors influence the bioavailability of astragalus compounds. Extraction methods significantly impact which compounds are present in a preparation and in what concentrations. Water decoctions, the traditional preparation method, effectively extract polysaccharides but are less efficient for extracting flavonoids and saponins.

Alcohol extractions (typically 30-70% ethanol) yield higher concentrations of flavonoids and saponins but lower polysaccharide content. Dual extraction methods that combine both water and alcohol extraction phases may provide a more comprehensive phytochemical profile. The presence of food in the gastrointestinal tract affects astragalus bioavailability in compound-specific ways. The absorption of flavonoids may be enhanced when taken with meals containing fats, which can increase solubilization and extend gastrointestinal transit time.

Conversely, food may delay the absorption of water-soluble polysaccharides through physical interference with access to absorption sites. Individual factors including age, genetic polymorphisms in metabolizing enzymes, gut microbiome composition, and gastrointestinal health status can significantly influence astragalus bioavailability. For example, variations in UDP-glucuronosyltransferase (UGT) enzymes, which are involved in flavonoid metabolism, can affect the bioavailability and half-life of these compounds. Several approaches have been investigated to enhance the bioavailability of astragalus compounds.

Liposomal formulations have shown promise for improving the bioavailability of astragaloside IV, with one study demonstrating a 5-fold increase in bioavailability compared to the free compound. Nanoparticle delivery systems, including polymer-based nanoparticles and solid lipid nanoparticles, have been developed to protect astragalus compounds from degradation and enhance their absorption. Enzymatic modification of astragalus polysaccharides to reduce molecular weight has been shown to improve absorption while maintaining biological activity. Co-administration with bioavailability enhancers such as piperine (from black pepper) may inhibit glucuronidation of flavonoids, potentially extending their half-life and enhancing effects.

The metabolism and elimination of astragalus compounds follow diverse pathways. Polysaccharides that are not absorbed may be partially fermented by gut microbiota, producing short-chain fatty acids that may contribute to the herb’s health benefits through indirect mechanisms. Absorbed polysaccharide fragments are primarily eliminated through renal excretion. Flavonoids undergo extensive phase II metabolism, with the resulting conjugates being eliminated through both biliary and renal routes.

Some conjugates may undergo enterohepatic circulation, extending their presence in the body. Saponins like astragaloside IV are metabolized through hydrolysis and oxidation, with the metabolites being eliminated primarily through fecal excretion. The pharmacokinetic profile of astragalus compounds varies by specific molecule. Studies in rats have shown that after oral administration, astragaloside IV reaches maximum plasma concentration (Cmax) in 0.5-2 hours, with an elimination half-life of approximately 3-4 hours.

Calycosin and formononetin typically reach Cmax within 0.5-1 hour, with elimination half-lives of 1-2 hours for the parent compounds and 3-5 hours for their conjugated metabolites. Despite the relatively short plasma half-lives of many astragalus compounds, the biological effects often persist longer than would be predicted by pharmacokinetic parameters alone. This suggests that these compounds may trigger sustained cellular responses or accumulate in target tissues, aspects that require further investigation.

Astragalus has a well-established safety profile based on both its long history of traditional use and modern clinical research. It is generally recognized as safe (GRAS) for most individuals when used appropriately, though certain considerations and precautions are warranted for specific populations and situations. Acute toxicity studies in animal models have demonstrated the remarkable safety of astragalus preparations. The LD50 (lethal dose for 50% of test animals) for oral administration of astragalus extracts is extremely high, typically exceeding 5,000 mg/kg body weight, indicating very low acute toxicity.

In human clinical trials, astragalus has been administered at doses ranging from 500 mg to 30 grams daily for periods of up to 6 months with no serious adverse effects reported. The most commonly reported side effects in clinical studies are mild and transient, including digestive symptoms such as nausea, diarrhea, or abdominal discomfort, which occur in approximately 2-5% of participants. These effects are typically dose-dependent and resolve with dosage reduction or temporary discontinuation. Allergic reactions to astragalus are rare but have been documented.

Individuals with known allergies to plants in the Fabaceae (legume) family, which includes peas, beans, and soybeans, may have a higher risk of allergic reactions to astragalus and should exercise caution. Symptoms of allergic reactions may include skin rash, itching, swelling, or respiratory symptoms. Several specific populations require particular consideration regarding astragalus use. Pregnant and breastfeeding women should approach astragalus use with caution.

While astragalus has been used traditionally during pregnancy in Chinese medicine, particularly for preventing miscarriage, modern clinical safety data in this population is limited. The general recommendation is to avoid therapeutic doses during pregnancy and breastfeeding unless specifically advised by a healthcare provider familiar with herbal medicine. For individuals with autoimmune conditions, theoretical concerns exist that astragalus’s immune-stimulating properties might exacerbate disease activity in certain autoimmune conditions, particularly those characterized by overactive immune responses. However, clinical evidence for such effects is limited, and some research suggests that astragalus may actually help modulate immune function in a beneficial way for certain autoimmune conditions.

Nonetheless, individuals with autoimmune diseases should consult with healthcare providers before using astragalus and should be monitored for any changes in disease activity if they do use it. Individuals taking immunosuppressive medications, including those prescribed for organ transplantation or autoimmune conditions, should exercise caution with astragalus due to potential interactions with the intended immunosuppressive effects of these medications. Theoretical concerns exist regarding potential interactions between astragalus and certain medications, though clinical evidence for significant interactions is limited. Astragalus may potentially interact with medications metabolized by cytochrome P450 enzymes, particularly CYP3A4, though the clinical significance of these interactions appears to be minimal in most cases.

Astragalus may enhance the effects of antihypertensive medications due to its own mild hypotensive properties, potentially necessitating dosage adjustments. Similarly, it may enhance the effects of hypoglycemic medications in individuals with diabetes, requiring careful monitoring of blood glucose levels. Astragalus may theoretically interact with anticoagulant and antiplatelet medications due to its mild effects on platelet aggregation, though significant bleeding events have not been reported in clinical studies. Long-term safety data from controlled studies extending beyond 6 months is limited, though the herb’s long history of traditional use provides some reassurance regarding long-term safety.

No evidence of cumulative toxicity or delayed adverse effects has been reported in the available literature. Regarding quality and contamination concerns, as with all botanical supplements, astragalus products should be sourced from reputable manufacturers who implement appropriate quality control measures. Potential issues include misidentification or adulteration with other Astragalus species (some of which contain toxic compounds like swainsonine), contamination with heavy metals, pesticides, or microorganisms, and inconsistent levels of active compounds. Standardized extracts with specified levels of marker compounds (such as polysaccharides or astragaloside IV) from reputable sources help mitigate these concerns.

No significant organ-specific toxicities have been identified for astragalus in either preclinical or clinical studies. Comprehensive toxicology studies have not demonstrated hepatotoxicity, nephrotoxicity, cardiotoxicity, or neurotoxicity at therapeutic doses. In fact, astragalus has demonstrated protective effects against various forms of organ damage in numerous experimental models. The safety profile of astragalus in children has not been extensively studied in clinical trials, though traditional use includes pediatric applications.

When used in children, dosage should be adjusted based on weight or age, typically at 25-50% of the adult dose depending on the child’s age. It’s worth noting that while astragalus is generally safe, the quality of commercial products can vary significantly. Products should be purchased from reputable manufacturers who provide information about standardization, testing for contaminants, and good manufacturing practices. In summary, astragalus demonstrates a favorable safety profile when used appropriately, with minimal risk of serious adverse effects.

The most common side effects are mild gastrointestinal symptoms that typically resolve with dosage adjustment. Specific populations, including pregnant women, those with autoimmune conditions, and individuals on certain medications, should exercise additional caution and seek professional guidance before use.

The quality, efficacy, and safety of astragalus supplements are significantly influenced by sourcing practices, including cultivation methods, harvesting techniques, geographical origin, and processing procedures. Understanding these factors is essential for obtaining high-quality astragalus products with optimal therapeutic potential. Astragalus membranaceus and Astragalus mongholicus (syn. A.

membranaceus var. mongholicus) are the two primary species used medicinally and recognized in pharmacopeias. These closely related species have similar chemical compositions and therapeutic properties. However, the genus Astragalus contains over 2,000 species worldwide, many of which lack medicinal value or may even contain toxic compounds like swainsonine.

Proper species identification is therefore crucial for both safety and efficacy. The geographical origin of astragalus significantly influences its phytochemical profile and therapeutic properties. Traditionally, astragalus from specific regions in northern China, particularly Inner Mongolia, Shanxi, and Heilongjiang provinces, is considered superior in quality. These regions have the appropriate climate, altitude, and soil conditions for optimal growth and phytochemical development.

Research has demonstrated that astragalus grown in these traditional regions typically contains higher levels of key bioactive compounds, including astragalosides and polysaccharides, compared to the same species grown in non-traditional regions. For example, studies have shown that astragalus from Inner Mongolia may contain up to 30-40% higher levels of astragaloside IV compared to the same species grown in southern Chinese provinces. The age of the astragalus plant at harvest significantly impacts quality. Traditional practice dictates that astragalus roots should be harvested from plants that are 4-7 years old for optimal medicinal value.

Younger roots typically contain lower concentrations of bioactive compounds, while roots from plants older than 7 years may become too woody and fibrous, with potentially diminished bioavailability of active compounds. The optimal harvest time is typically in autumn (September to October) after the plant’s aerial parts have begun to wither but before the first frost. This timing corresponds to the highest concentration of bioactive compounds in the roots, as the plant redirects resources to its root system for winter storage. Cultivation methods significantly impact astragalus quality.

Traditionally grown astragalus, cultivated without synthetic pesticides or fertilizers in its native habitat, often contains a more balanced and complete phytochemical profile. However, to meet increasing global demand, commercial cultivation has expanded, sometimes with intensive agricultural practices. Organically grown astragalus generally contains fewer pesticide residues and may have higher levels of certain defensive phytochemicals that the plant produces in response to natural environmental stressors. Wild-crafted astragalus is increasingly rare and faces sustainability concerns, though some producers still offer wild-harvested products, particularly from remote regions of Inner Mongolia.

Post-harvest processing techniques significantly influence the final quality of astragalus products. Traditional processing involves cleaning the roots, removing the fine rootlets and crown, slicing the main roots either longitudinally or transversely, and drying them thoroughly. Some traditional preparations involve honey-curing (processing with honey), which is believed to enhance the herb’s tonifying properties and improve its flavor. Modern processing may include additional steps such as sulfur fumigation to preserve color and prevent insect infestation.

However, this practice can degrade certain bioactive compounds and leave potentially harmful residues. High-quality products should specify that they are unsulfured or tested for sulfur dioxide residues. For extract production, the extraction method significantly impacts which compounds are present in the final product. Water extraction yields higher levels of polysaccharides, while alcohol extraction (typically 30-70% ethanol) yields higher levels of flavonoids and saponins.

Dual extraction methods that combine both water and alcohol extraction phases may provide a more comprehensive phytochemical profile. The quality of commercial astragalus products varies considerably. High-quality products should provide information about species, geographical origin, cultivation methods, processing techniques, and standardization parameters. Standardization typically focuses on key marker compounds such as astragaloside IV (for saponins), calycosin or formononetin (for flavonoids), or total polysaccharide content.

Products standardized to multiple marker compounds generally provide more reliable therapeutic effects than those standardized to a single compound or not standardized at all. Third-party testing and certification provide additional quality assurance. Reputable manufacturers often provide certificates of analysis verifying the identity, potency, and purity of their products, including testing for contaminants such as heavy metals, pesticides, microbiological contaminants, and mycotoxins. Sustainability considerations are increasingly important in astragalus sourcing.

The growing global demand has led to concerns about overharvesting in some regions. Sustainable sourcing practices include cultivation rather than wild harvesting, appropriate crop rotation, organic or biodynamic farming methods, fair labor practices, and responsible use of water and other resources. Some producers now offer astragalus products certified by sustainability-focused organizations. For consumers and practitioners seeking high-quality astragalus products, key indicators of quality include clear specification of species (A.

membranaceus or A. mongholicus), information about geographical origin (preferably traditional growing regions in northern China), details about standardization and active compound content, third-party testing certification, and transparency about cultivation and processing methods. Products that provide this level of detail typically represent higher quality and are more likely to deliver the expected therapeutic benefits.

Astragalus has a rich and extensive history of medicinal use spanning over two millennia, primarily in East Asian medical traditions but eventually spreading to other parts of the world. This historical context provides valuable insights into the herb’s traditional applications and cultural significance. The earliest documented medicinal use of astragalus appears in the Shennong Bencao Jing (Divine Farmer’s Classic of Materia Medica), compiled around 200 CE but believed to contain much older knowledge. In this foundational text of Chinese herbal medicine, astragalus (Huang Qi) was classified as a superior herb, the highest category reserved for herbs that could strengthen vital energy, promote longevity, and be taken regularly without toxicity.

The text described astragalus as sweet in taste and slightly warm in nature, with properties that could ‘tonify the surface, promote the growth of muscle and flesh, and strengthen the defensive Qi.’ During the Han Dynasty (206 BCE-220 CE), astragalus was primarily used to treat surface deficiency conditions characterized by spontaneous sweating, weakness, and susceptibility to external pathogens. Its applications expanded significantly during the Tang Dynasty (618-907 CE), when physicians began using it more extensively for Qi deficiency conditions affecting internal organs, particularly the spleen and lungs. The Tang Dynasty physician Sun Simiao, in his work Qianjin Yaofang (Thousand Golden Essential Prescriptions), documented numerous formulas containing astragalus for treating chronic fatigue, weakness after illness, and various deficiency conditions. The Song Dynasty (960-1279 CE) marked a significant advancement in the understanding of astragalus’s properties and applications.

The influential work Bencao Tujing (Illustrated Classic of Materia Medica) by Su Song provided detailed botanical descriptions and expanded medicinal applications of astragalus. During this period, astragalus became increasingly recognized for its ability to ‘tonify the middle Jiao and augment Qi,’ making it a primary herb for treating digestive weakness, fatigue, and prolapse of organs due to Qi deficiency. The Ming Dynasty (1368-1644 CE) saw further refinement in the understanding of astragalus’s therapeutic properties. The landmark pharmacopeia Bencao Gangmu (Compendium of Materia Medica) by Li Shizhen, completed in 1578, provided comprehensive information on astragalus, including detailed descriptions of its appearance, cultivation, processing methods, and expanded medicinal applications.

Li Shizhen documented astragalus’s use for treating ‘wasting and thirsting disorder’ (a condition similar to diabetes), chronic ulcers, and various types of edema, significantly broadening its clinical applications. During the Qing Dynasty (1644-1912), astragalus became increasingly incorporated into complex formulas for treating chronic and deficiency conditions. The text Yizong Jinjian (Golden Mirror of Medicine) compiled under the Qianlong Emperor in 1742 included numerous astragalus-containing formulas for treating deficiency conditions, particularly those affecting the elderly. One of the most significant developments in the historical use of astragalus was the creation of the formula Buzhong Yiqi Tang (Tonify the Middle and Augment Qi Decoction) by the Song Dynasty physician Li Dongyuan around 1249 CE.

This formula, with astragalus as the primary herb, was designed to treat a pattern of ‘sinking Qi’ characterized by fatigue, weak digestion, and prolapse of organs. This formula remains one of the most widely used astragalus-containing preparations in traditional Chinese medicine today. In Korean traditional medicine (Hanbang), astragalus has been used since at least the Goryeo Dynasty (918-1392 CE), with applications similar to those in Chinese medicine but with greater emphasis on its warming properties for treating cold conditions. The Korean medical text Dongui Bogam (Precious Mirror of Eastern Medicine), compiled by Heo Jun in 1613, contains numerous references to astragalus for strengthening the body’s resistance to disease.

In Japanese Kampo medicine, which developed from Chinese medicine but evolved distinct characteristics, astragalus (known as Ogi) has been used since the Heian period (794-1185 CE). The Japanese pharmacopeia Honzō Wamyō (Japanese Names of Herbs), compiled in the 10th century, includes astragalus among its medicinal plants. Astragalus was introduced to Western medicine relatively late compared to some other Asian medicinal herbs. In the 19th century, European botanists and physicians traveling in China documented the medicinal use of astragalus, but it remained largely unknown in Western medical practice until the 20th century.

The herb gained increased attention in the West during the 1970s and 1980s, particularly after Chinese research on its immune-enhancing properties was translated and published in English-language journals. Modern scientific interest in astragalus was significantly stimulated by research conducted at the Chinese Academy of Medical Sciences in the 1970s, which investigated the herb’s effects on immune function. This research, which demonstrated astragalus’s ability to enhance various aspects of immune response, coincided with growing Western interest in alternative medicine and immune-supporting natural products. Throughout its long history, astragalus has been prepared and administered in various forms.

Traditional preparations include decoctions (the herb simmered in water), often combined with other herbs in formulas tailored to specific conditions. Honey-cured astragalus (processed with honey before decoction) was traditionally used to enhance its tonifying properties for severe deficiency conditions. Astragalus was also historically incorporated into medicinal wines, pills, and external applications for wounds and sores. The historical applications of astragalus align remarkably well with modern research findings on its biological activities, including its immunomodulatory, cardiovascular protective, adaptogenic, and anti-diabetic effects.

This convergence of traditional wisdom and scientific validation has contributed to astragalus’s enduring popularity and its transition from traditional medicine into contemporary healthcare practices worldwide.