Traditional Chinese Medicine
Originating > 2000 yr ago, traditional Chinese medicine (TCM) is a medical system based on the philosophy that illness results from improper flow of the life force (qi). The movement of qi is restored by balancing the opposing forces of yin and yang, which manifest in the body as cold and heat, internal and external, and deficiency and excess.
Various practices are used to preserve and restore qi and thus health. Most commonly used are
Other practices include diet, massage, and meditative exercise called qi gong.
TCM often uses diagnostic categories that do not correspond to current scientific understanding of biology and illness (eg, general deficiency, excess of yin or yang).
Obtaining high-quality evidence is difficult, mainly because the active ingredients in TCM herbs are not purified, are often unidentified, and may be numerous. Thus, determining the dose is difficult or impossible, and the dose may vary from one source of herbs to another. Information about bioavailability, pharmacokinetics, and pharmacodynamics is usually unavailable. Also, active ingredients may interact with each other in complex and variable ways.
Chinese herbal medicine traditionally uses formulas containing mixtures of herbs to treat various disorders. Traditional formulas can be studied as a whole, or each herb in the formula can be studied separately. One herb, used by itself, may not be as effective and may have adverse effects. Nevertheless, current conventional research favors study of single herbs to better control for variables. Another problem is the large number of herbal mixtures that could be studied.
Studies of TCM herbs and herbal mixtures for irritable bowel syndrome have had mixed results, and reviews of these studies conclude that more rigorous studies are required.
Preliminary studies of Tripterygium wilfordii(thunder god vine) has demonstrated anti-inflammatory properties and suggested clinical efficacy in treating RA, but reviews1 have found that existing evidence is insufficient to prove efficacy and concluded that more research is needed.
Preliminary studies2 show that Astragalus may improve quality of life for patients being treated with chemotherapy for lung cancer, but it does not prolong survival or slow progression of cancer, as assessed by biomarkers.
1Liu Y, Tu S, Gao W, et al:Extracts of Tripterygium wilfordii Hook F in the treatment of rheumatoid arthritis: a systemic review and meta-analysis of randomised controlled trials. Evid Based Complement Alternat Med 410793, 2013. [Epub 2013 Dec 4.]
2McCulloch M, See C, Shu XJ, et al: Astragalus-based Chinese herbs and platinum-based chemotherapy for advanced non-small-cell lung cancer: meta-analysis of randomized trials. J Clin Oncol20;24(3):419–30, 2006.
One problem is the standardization and quality control of Chinese herbs. Many are unregulated in Asia; they may be contaminated with heavy metals from polluted ground water or may be adulterated with drugs such as antibiotics or corticosteroids. Ingredients are often substituted, partly because the names of the herbs are translated incorrectly. A 2013 study1 found that 32% of herbal supplements did not contain the main active ingredient on the label, 20% contained contaminants (physiologically active compounds other than the ingredients desired or on the label), and another 21% contained fillers not listed on the label. However, high-quality products are available through certain manufacturers that comply with FDA Good Manufacturing Practices.
In herbal mixtures, adverse effects may also result from interactions between active ingredients.
1Newmaster SG, Grguric M, Shanmughanandhan D, et al: DNA barcoding detects contamination and substitution in North American herbal products. BMC Med 11;11–222, 2013.