About Herbs

Bottom Line: Astragalus may have immunostimulant effect

From the research that has been conducted with astragalus, scientists believe that it works by stimulating several factors of the immune system. In laboratory studies, astragalus extracts augment the activity of monocytes, natural killer cells, and lymphocytes, even when their activity is suppressed by substances such as steroids. In addition, astragalus reversed immune suppression from cyclophosphamide (a common chemotherapy drug) in rats.

Astragalus extracts also protect liver cells from chemical injury in animals and in laboratory studies. Studies conducted in China suggest that astragalus may also protect the kidneys when used in combination with the herb angelica. In studies using senile rats, astragalus increased the ability of their brain cells to respond to stimuli, but it is still unknown if these effects occur in humans.

An herbal formula containing astragalus has been shown to reduce fatigue in athletes by increasing uptake and use of oxygen.

End-stage kidney disease:
Thirty-one patients with end-stage kidney disease on hemodialysis were followed to test whether astragalus could improve their immune response. Patients received either intravenous astragalus extract or placebo for two months. Compared to the placebo group, the astragalus group had significantly higher levels of IL-2, a substance that stimulates the growth of immune cells and their response to disease. However, this does not necessarily indicate that astragalus improved immune response in these patients. It would be more helpful to know whether astragalus helped these patients fight off disease or live longer, which this study does not address.

Astragalus is often used in combination with other botanicals in Traditional Chinese Medicine. Clinical trials conducted in China suggest astragalus-based herbal formulas may enhance the efficacy and reduce the side effects of certain chemotherapy.

None known

Astragalus membranaceus

Huang chi, huang qi, milk vetch, Radix astragali

Derived from the root of the plant. This product is primarily used for its immune stimulating properties. In vitro, animal, and anecdotal human data show reduction of immune suppression following chemotherapy ^{(6) (13)}. Astragalus-based herbal formulas may enhance the effect of platinum-based chemotherapy ⁽¹²⁾. Chinese studies suggest that astragalus, when used with angelica, has renal protective effects ⁽⁸⁾.  An herbal formula using astragalus as major ingredient has been shown to reduce fatigue in athletes ⁽⁹⁾. Astragalus increases M-cholinergic receptor density in senile rats ⁽⁷⁾, which suggests that it may have a role in combating senility. It can also delay chemical-induced hepatocarcinogenesis in rats ⁽¹⁰⁾. To date, no significant adverse events have been reported. Patients on immunosuppressants (e.g., tacrolimus or cyclosporin) should not take this supplement. Herbal astragalus preparations should be administered only by oral route.

Astragalus works by stimulating several factors of the immune system. The polysaccharides potentiate in vitro the immune-mediated antitumor activity of interleukin-2 ⁽¹¹⁾,improve the responses of lymphocytes from normal subjects and cancer patients, and enhance the natural killer cell activity of normal subjects and potentiate activity of monocytes ⁽⁵⁾. The saponins potentiate natural killer cell (NKc) activity and restore steroid-inhibited NKc activity in vitro. They also increase phagocytosis and demonstrate hepatoprotective effects on chemically induced liver injury in vitro ⁽⁸⁾ and in vivo ⁽¹⁰⁾. Chinese studies suggest that astragalus, when used with angelica, has renal protective effects by mediating gene expression. Astragalus increases M-cholinergic receptor density in senile rats. This suggests that astragalus may have a role in combating brain senility ⁽⁷⁾. Herbal formula containing astragalus can reduce fatigue in athletes by increasing uptake and utility of oxygen. ⁽⁹⁾

No adverse effects have been reported.

Immunosuppresants: Astragalus may antagonize the effects of immunosuppresants such as tacrolimus and cyclosporine.
Aldesleukin: Concomitant treatment with astragalus has resulted in a 10-fold potentiation of tumor-cidal activity with decreased side effects.
Cyclophosphamide: Astragalus may decrease immunosuppression following treatment.
^{(4) (5) (6)}

Most of the clinical trials on astragalus were conducted in China using multiple-herbal formulas that contain astragalus as the major component. The selection of herbs is based on Traditional Chinese Medicine.

Qun L, et al. Effects of astragalus on IL-2 / IL-2R system in patients with maintained hemodialysis (letter). Clin Neph 1999;52:333-4.
Prospective evaluation of 31 patients in end-stage renal disease, on hemodialysis. Participants were randomized to receive either intravenous astragalus or placebo. After 2 months of treatment, the astragalus group had significantly higher levels of IL-2 compared to placebo.

McCulloch M, et al. Astragalus-based Chinese herbs and platinum-based chemotherapy for advanced non-small-cell lung cancer: Meta-analysis of randomized trials. J clin Oncol 2006;24(3):419-430.
This analysis sought to determine whether Chinese herbal medicine containing Astragalus increases the effectiveness of platinum-based chemotherapy for advanced non-small-cell-lung cancer.  Thirty-four randomized studies involving 2,815 patients were analyzed. Results suggest that when used in conjunction with platinum-based chemotherapy, Astragalus-based medicine improved survival, tumor response, performance status, and reduced chemotherapy toxicity when compared with chemotherapy alone.
However, the low quality of the studies analysed is a drawback and the results are therefore, not conclusive. Well-designed studies are warranted.

Taixiang W, et al. Chinese medical herbs for chemotherapy side effects in colorectal cancer patients (Review). The Cochrane Database Syst Rev 2005; (1):CD004540.
Four clinical trials were included in this review to assess the effectiveness of Astragalus (Huangqi) compounds on the quality of life, side effects of chemotherapy, and on adverse effects in colorectal cancer patients. A decoction of Huangqi compounds was used in combination with chemotherapy in three studies, whereas the fourth study compared Huangqi compounds with two other Chinese herbal formulas. Patients who were given Huangqi compounds experienced a reduction in nausea and vomiting along with a decrease in the rate of leucopenia and an increase in CD3, CD4 and CD8 subsets of T-lymphocytes when compared to those treated with chemotherapy alone in the three studies or with other Chinese formulas in the fourth study.
Use of Chinese herbal medicine along with chemotherapy appears promising for patients with colorectal cancer; however, a major limitation of this review is that it includes only four studies and the studies are of poor quality. Further properly designed trials are needed to confirm these observations.