The efficacy and safety of Chinese herbal medicines

The uses and practice of traditional Chinese medicines (TCM) date back centuries and are steeped in customs that encompass ancestral beliefs (concerning health), drug lore and “an understanding of natural laws” (Hesketh & Zhu, 1997; Unschuld, 1999). Today TCM (on its own or in conjunction with conventional medicine) is an integral component of healthcare systems in the Far East and is used to treat disease and to promote health and wellbeing (Hesketh & Zhu, 1997; Scheid, 2000; Bodeker, 2001; Wang & Ren, 2002). Over the past decade, Western medicine has witnessed the keen embracing of certain elements of TCM, especially Chinese herbal medicines (CHM) and their commercial derivatives. These medicines are said to possess numerous properties and as a consequence are used to treat a variety of diseases including arthritis, cancer, asthma and allergies (Brooks & Lowenthal, 1977; But & Chang, 1996; Chan & Critchley, 1996). Ganoderma lucidum, or ‘Lingzhi’, the focus of the paper by Wachtel-Galor et al. (2004b) in this issue of the British Journal of Nutrition is a prime example of the multifarious nature of CHM. G. lucidum is a very popular Chinese medicinal fungus, which has long been used as a sedative. It is reported to possess anti-tumour, anti-hepatotoxic, antinociceptive and immunomodulatory properties and has been used in the treatment of hypercholesterolaemia and hypertension (Jong & Birmingham, 1992; Lin et al. 1995; Koyama et al. 1997; Wang et al. 1997, 2002; Wasser & Weis, 1999; Bao et al. 2001a,b; Liu et al. 2002). Moreover, the immunomodulatory properties of G. lucidum have been exploited in the development of possible treatments for both allergic asthma and food allergy (Li et al. 2000, 2001). G. lucidum is also used as a dietary supplement and health food (Chiu et al. 2000). With the increasing use of CHM, such as G. lucidum, come the questions concerning their safety, regulation, efficacy and mode of action (Chan et al. 1993; Chan & Critchley, 1996; Tang et al. 1999; Ernst, 2000, 2003; Fugh-Berman, 2000; Mills, 2001). The use of CHM has been connected to a number of adverse effects resulting in nephropathy, acute hepatitis, coma and fever. In addition, neurological, cardiovascular and gastrointestinal problems have also been associated with CHM (Chan et al. 1993; Vanherweghem et al. 1993; Chan & Critchley, 1996; Lord et al. 1999; Nortier et al. 2000; Park et al. 2001). Cases of poisoning have been linked to variations in the chemical composition of different brands of the same herb. Such differences may arise as a result of inadequate processing (processing normally involves soaking and boiling the raw material) resulting in toxins being retained, and adulteration with cheaper substitutes (Chan & Critchley, 1996; Fugh-Berman, 2000; Li & Sampson, 2003). (Adulteration may also obscure the true benefits of CHM as well as contribute to them (Keane et al. 1999).) Cases of poisoning may also be attributed to heavy metals (Cd, Pb, Tl and Hg) present in both unprocessed CHM and their commercial derivatives (Wong et al. 1993; Chan & Critchley, 1996; Chiu et al. 2000). The misclassification of species and the mistaken substitution of Chinese herbs have also given rise to serious adverse affects (Chan et al. 1993; Vanherweghem et al. 1993; But, 1994; Chan & Critchley, 1996; Fugh-Berman, 2000). For example, a product believed to contain ‘Siberian ginseng’ but on analysis was shown to contain Chinese Silk Vine, has been linked to a case of neonatal androgenisation in North America (Koren et al. 1990; Awang, 1991). Misidentification of CHM can also lead to erroneous explanations concerning their mode of action. In correspondence concerning the anti-allergic properties of the CHM ‘Food Allergy Herbal Formula-1’ (FAHF-1), the incorrect identification of the chemical structure of one of its components (G. lucidum) led to ‘misleading conclusions’ about the causes of FAHF-1’s immunomodulatory action (Li et al. 2001; Claman, 2002; Towers, 2003; Li & Sampson, 2003). Concerns about CHM have been further reinforced by the potential for their interactions with conventional medicines causing effects that may ultimately result in modifications to the action(s) of the conventional medicines (Chan & Critchley, 1996; Chen et al. 2002; Fugh-Berman, 2000). An example of such an interaction is that of warfarin and Angelica sinensis (dong quai) or Salvia miltiorrhiza (danshen). Evidence suggests that the bioavailability and elimination rate of warfarin, plus platelet function, are affected by these CHM (Chan & Critchley, 1996; Fugh-Berman, 2000). Clearly these issues highlight the need for further in-depth research on CHM and other herbal medicines. The National Center for Complementary and Alternative Medicine (NCCAM; http://nccam.nih.gov), a US Congress-funded body, actively supports research and development in the area of CHM. In addition, the Department of Complementary Therapies at Exeter University in the UK has highlighted the need to adhere to rigorous scientific methodology in the carrying out of research on CHM and other alternative and complementary therapies (www.ex.ac.uk/FACT). In studies on CHM, a variety of approaches have been used. Some studies have focused on analysis, others on biological activities, safety, bioavailability and mode of action using either cell or animal models (Lin et al. 1995; Kawagishi et al. 1997; Chiu et al. 2000; Bao et al. 2001a,b; Chen et al. 2002; Wang et al. 2002; Xu et al. 2003). Many studies have used randomised controlled trials (RCT) to address the question of efficacy. A systematic British Journal of Nutrition (2004), 91, 171–173 DOI: 10.1079/BJN20031060 q The Author 2004