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Supporting the Immune System in the Winter
By Maureen Williams, ND
During the cold, dark days of winter, many people find themselves especially susceptible to infection. Engaging and strengthening the body’s natural defense network—the immune system—is the best way to prevent viruses and bacteria from taking hold and to beat infections quickly. Medicinal herbs stimulate different aspects of the immune system, and many have direct antiviral and antibacterial constituents that add extra protection against infection. Nutrients necessary for healthy immune function, such as vitamin A and zinc, can complement the actions of the herbs.
Some immuno-supportive herbs have gained wide attention and popularity, such as echinacea (Echinacea spp) and elderberry (Sambucus nigra), but some others have remained less well known despite evidence suggesting their effectiveness. The brief monographs that follow might serve to encourage you to think about expanding your choice of implements when developing winter immune support programs.
Isatis/Isatis tinctoria
Although widely used in traditional Chinese medicine and Ayurveda, isatis is not well known to most western herbalists. Historical uses of isatis include prevention and treatment of acute infections, particularly when marked by significant inflammation. Its topical and systemic anti-inflammatory effects have been documented by several research teams, [i] [ii] [iii] [iv] and its alkaloids have demonstrated broad antifungal effects in vitro, [v] as well as antibacterial effects against Staphylococcus aureus. [vi] Other studies have found that isatis has antiviral effects in vitro against the influenza virus, [vii] HSV, [viii] and cytomegalovirus. [ix]
The infection-fighting capacity of isatis has been suggested by the findings of several studies. One in vitro study found that isatis enhanced the effectiveness of four antibiotics against strains of Staphylococcus aureus, including a Methicillin-resistant strain. [x] Isatis extract was also found to improve the immune response and have antibacterial effects against chronic Pseudomonas aeruginosa lung infection in an animal model of cystic fibrosis. [xi] In a controlled one-week trial, isatis eye drops were as effective as antibiotic eye drops in 200 people with acute bacterial conjunctivitis. [xii]
Astragalus/Astragalus membranaceus
Like isatis, astragalus comes to the western herbal pharmacy from Asia, where it has been used for centuries as an immune tonic and digestive aid. Preliminary studies support these uses by showing that astragalus can stimulate human immune cell proliferation in vitro and restore immune activity in older and immuno-suppressed mice, [xiii] and can stimulate immune and anti-tumor activity in mice. [xiv] [xv] Another study found that astragalus stimulated immune cell activity against Mycobacterium tuberculosis. [xvi] Astragalus’ immuno-supportive potential was also implied by a trial in which healthy people taking astragalus tincture experienced immune cell stimulation that was measurable within 24 hours and lasted at least seven days. [xvii]
Chinese researchers have conducted a number of controlled trials, and in them, treatment with astragalus led to increased immune cell levels in people with aplastic anemia, [xviii] herpes simplex keratitis, [xix] congestive heart failure, [xx] and abdominal trauma, [xxi] as well as in children with acute leukemia. [xxii] In another controlled trial, astragalus improved response to treatment and immune function in cyclophosphamide-treated people with lupus nephritis. [xxiii]
Astragalus appears to have antiviral properties, and findings from studies done in China suggest that Astraglus might be useful in the treatment of HSV [xxiv] [xxv] [xxvi] and HBV. [xxvii] Antiviral activity against coxsackie virus [xxviii] [xxix] and cytomegalovirus [xxx] have also been demonstrated.
Atractylodes/Atraactylodes macrocephalus
Atractylodes is an important herb in traditional Chinese medicine. It has been used historically as a general tonic, digestive aid, and disinfectant. [xxxi] Atractylodes is a common ingredient in cold and flu formulas because it is believed to relieve fever and chills and help restore energy. It has been found to stimulate immune cell production in the spleens of experimental animals, [xxxii] and exhibited antiviral effects against human immunodeficiency virus (HIV) in vitro. [xxxiii]
Atractylodes has a number of other properties that have led to its common usage. It has been shown to stimulate appetite, [xxxiv] and results from animal studies suggest that it might help regulate gastric emptying. [xxxv] [xxxvi] [xxxvii] Its diuretic effects make it a good choice for treating edema and its anti-inflammatory properties are well documented. [xxxviii] [xxxix] [xl] Traditional formulas that include Atractylodes were found to be helpful in treating eczema, [xli] [xlii] [xliii] and another Atractylodes-based formula was helpful in treating rheumatoid arthritis in animals. [xliv] There is also evidence that atractylodes can improve glucose tolerance and help prevent complications of diabetes. [xlv] [xlvi]
Siler/Saposhnikovia divaricata
Along with astragalus and atractylodes, siler is part of the yu ping feng formula, or jade screen formula, popular for treating people who are prone to catching colds and have low energy and a pale, weak appearance. Siler, which is also know as Ledebourellia or fangfeng, is used by practitioners of traditional Chinese medicine to expel excessive wind, and its indications include illnesses marked by wind characteristics such as fever, chills, headache, sore throat, red eyes, and generalized body pain.
Findings from preliminary research suggest that siler has antioxidant, [xlvii] anti-inflammatory, [xlviii] and analgesic properties. [xlix] Extracts from siler have also demonstrated anti-proliferative effects on cancer cell lines in vitro. [l] [li] Other in vitro research has identified an immunostimulatory polysaccharide from siler. [lii] [liii]
Licorice/Glycyrrhiza glabra
Licorice is perhaps best known for its demulcent effect on the gastric and respiratory mucosae, and is also widely used as an adrenal hormone agonist. Its usefulness in treating colds and flus is not limited to its ability to soothe and expectorate, as its antiviral and antibacterial effects have been established in a number of studies.
One licorice constituent, glycyrrhizin (the calcium and potassium salts of glycyrrhizic acid), has received particular attention for its antiviral potential. Glycyrrhizin was found to be effective at stopping Japanese encephalitis virus, [liv] and was the most potent of a group of antiviral compounds at inhibiting replication of the coronavirus linked to severe acute respiratory syndrome (SARS). [lv] An animal trial found glycyrrhizin effective against influenza virus, [lvi] and there is in vitro evidence that licorice extract is active against the respiratory syncytial virus, or RSV, a common cause of respiratory illness that can be life-threatening in infants and young children, [lvii] [lviii] as well as the mononucleosis-causing Epstein-Barr virus (EBV). [lix]
Bacteria implicated in upper respiratory infections have also been shown to be vulnerable to the antimicrobial effects of licorice. One in vitro trial found several licorice constituents effective against streptococcus pyogenes, Haemophilus influenzae, and Moraxella catarrhalis. [lx]
Ginger/Zingiber officionale
Volatile oils give ginger root its distinctive aroma and flavor, and endow it with an abundance of medicinal properties. Ginger has been used for centuries as a circulatory stimulant and peripheral vasodilator, as well as antiemetic and expectorant. As its anticlotting and anti-inflammatory effects have become more evident, the breadth of its common use has extended to chronic conditions such as rheumatism and cardiovascular disease. [lxi] [lxii]
Ginger’s volatile oils are responsible for its antimicrobial actions that can help prevent and treat colds and flu. An alcohol extract of ginger demonstrated bactericidal effects against a number of bacteria collected from nasal secretions of people with cold symptoms, including Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae, and Haemophilus influenzae. [lxiii] Essential oils from ginger have also been found in vitro to have antiviral activity, in particular against rhinoviruses (the family of viruses responsible for the common cold) [lxiv] and influenza virus, [lxv] as well as HSV. [lxvi]
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