ⓒ The Korean Society of Ginseng 259 http://ginsengres.org pISSN: 1226-8453 eISSN: 2093-4947 Review J. Ginseng Res. Vol. 34, No. 4, 259-263 (2010) DOI:10.5142/jgr.2010.34.4.259 E-mail: Edzard.Ernst@pms.ac.uk Tel: +44-1392-424989, Fax: +44-1392-427562 * Corresponding author INTRODUCTION Ginseng has a long history of medicinal use [1-3]. To- day ginseng preparations are amongst the most popular and best-selling herbal medicines worldwide [4]. They are employed for a broad range of conditions – some- times, sadly, without sufficient proof [5]. A clear distinction between Siberian (sometimes also called Russian) ginseng, Eleutherococcus senticosus, and Asian ginseng, Panax ginseng, is important [6]. The genus Panax includes various species such as Panax quinque- foluis (American ginseng) and Panax japonicus (Japa- nese ginseng) [4]. The range of ginsenosides contained in Korean Panax ginseng has been reported to be larger than that in other species [7]. In the Korean tradition, several different ways of pre- paring and manufacturing Panax ginseng exist. Fresh ginseng is less than 4 years old; white ginseng is 4 to 6 years old and is dried after peeling; red ginseng is harvested when it is 6 years old, subsequently it is not skinned but steamed and then dried. The subject is further compli- cated by the fact that, according to several laboratory investigations, commercially available ginseng products are sometimes of less than optimal quality [8,9]. Thus negative trial results could theoretically be due to poor product quality rather than lack of efficacy. The aim of this ‘mini-review’ is to summarize the existing clinical evidence, mainly based on systematic reviews and meta- analysis, of all types of preparations of Panax ginseng. HOW TO DETERMINE CLINICAL EFFICACY Panax ginseng has been used for medicinal purposes for centuries. One might therefore assume that it has ‘stood the test of time’ and its therapeutic value is be- yond doubt. Yet we know that a long history of use often proves very little. It certainly does not conclusively demonstrate the efficacy nor the safety of the treatment in question. In order to show efficacy, we require a comparator, i.e., a control group. Without it, one can never be certain whether any observed change in health status after the administration of a therapy is due to the treatment. It might also be caused by a myriad of other factors includ- ing natural history of the disease or regression towards the mean. If we want to also exclude placebo-effects and Panax ginseng: An Overview of the Clinical Evidence Edzard Ernst * Complementary Medicine, Peninsula Medical School, Universities of Exeter & Plymouth, Exeter EX2 4NT, UK This overview is focused on Panax ginseng, one of the most commonly used herbal remedies. The currently available data regarding its clinical efficacy is somewhat confusing, despite the fact that many clinical trials and systematic reviews have been published. The risks of Panax ginseng seem to be only minor. Numerous mechanisms of action have been described. Fu- ture studies of this fascinating herbal remedy seem warranted but they should overcome the methodological limitations of the previous research. Keywords: Panax ginseng, Herbal medicine, Safety, Efficacy, Evidence This is an Open Access article distributed under the terms of the Cre- ative Commons Attribution Non-Commercial License (http://creativecom- mons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Received 16 Jul. 2010, Revised 24 Nov. 2010, Accepted 10 Dec. 2010