Maca (L. meyenii) for improving sexual function: a systematic review

Shin et al. BMC Complementary and Alternative Medicine 2010, 10:44 http://www.biomedcentral.com/1472-6882/10/44 RESEARCH ARTICLE Open Access Maca (L. meyenii) for improving sexual function: a systematic review Byung-Cheul Shin1, Myeong Soo Lee2,4*, Eun Jin Yang2, Hyun-Suk Lim3, Edzard Ernst4 Abstract Background: Maca (Lepidium meyenii) is an Andean plant of the brassica (mustard) family. Preparations from maca root have been reported to improve sexual function. The aim of this review was to assess the clinical evidence for or against the effectiveness of the maca plant as a treatment for sexual dysfunction. Methods: We searched 17 databases from their inception to April 2010 and included all randomised clinical trials (RCTs) of any type of maca compared to a placebo for the treatment of healthy people or human patients with sexual dysfunction. The risk of bias for each study was assessed using Cochrane criteria, and statistical pooling of data was performed where possible. The selection of studies, data extraction, and validations were performed independently by two authors. Discrepancies were resolved through discussion by the two authors. Results: Four RCTs met all the inclusion criteria. Two RCTs suggested a significant positive effect of maca on sexual dysfunction or sexual desire in healthy menopausal women or healthy adult men, respectively, while the other RCT failed to show any effects in healthy cyclists. The further RCT assessed the effects of maca in patients with erectile dysfunction using the International Index of Erectile Dysfunction-5 and showed significant effects. Conclusion: The results of our systematic review provide limited evidence for the effectiveness of maca in improving sexual function. However, the total number of trials, the total sample size, and the average methodological quality of the primary studies were too limited to draw firm conclusions. More rigorous studies are warranted. Background Sexual problems (or sexual dysfunction) are widespread and adversely affect mood, well-being, and interpersonal relationships [1]. They occur in 20%-30% of men and 40-45% of women according to 18 descriptive epidemiological studies from around the world [2]. Most sexual problems relate to sexual desire (interest in sex) in both females and males and male erectile dysfunction (ED) [2]. Current pharmacological interventions for the management of sexual problems include oral drugs, intrapenile therapies (intra-urethral suppositories and intracavernous injections) and penile prosthesis implantation for males and hormonal therapy for females. Although considerable advances have been made, the ideal treatment for ED has not been identified. The treatment for sexual problems in females is also problematic [3]. Furthermore, * Correspondence: 2 Division of Standard Research, Korea Institute of Oriental Medicine, Daejeon, South Korea Full list of author information is available at the end of the article pharmacological treatments have been shown to result in several adverse effects, including risk of cancer, headache, rhinitis and dyspepsia [4-6]. Non-pharmacological treatments of female sexual problems includes vaginal electromyography biofeedback, pelvic floor physical therapy, (group) cognitive behavioural therapy, transcutaneous electrical nerve stimulation, and vestibulectomy [7]. Herbal therapies for ED or sexual dysfunction in males and females include yohimbine (Pausinvstalia vohimbe), which is burdened with serious adverse effects [8-10], ginkgo (Ginkgo biloba) and red ginseng (Panax ginseng) [10,11]. Several other botanical therapies for sexual dysfunction have also been introduced [8,10,12]. These are also often used for improving sexual function in healthy subjects. Maca (Lepidium meyenii) is an Andean plant that belongs to the brassica (mustard) family. Maca has been used for centuries in the Andes to enhance fertility in humans and animals [12,13]. Preparations from the maca root have been reported to improve sexual © 2010 Shin et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Shin et al. BMC Complementary and Alternative Medicine 2010, 10:44 http://www.biomedcentral.com/1472-6882/10/44 function in healthy populations [13]. Although maca is a plant extract and not a drug, it is one of the most commonly cited “natural drugs” on the Internet for the improvement of sexual desire. The hypothesis that maca may be effective in improving sexual function is supported by several lines of evidence. Animal experiments suggest that maca has spermatogenic and fertilityenhancing activities, which are likely due to the phytosterols or phytoestrogens present in the maca [14]. Several in vivo studies have shown that maca may improve sexual behaviour and enhance androgen-like effects in rats [15,16]. Recent clinical trials have also suggested significant effects of maca for increasing sperm count and mobility and improving sexual function in humans [17,18]. The potential bioactive ingredients in maca include macaridine, macamides, macaene, gluosinolates, maca alkaloid, and maca nutrients [14]. However, these data are insufficient for determining whether maca is clinically effective. Currently, no systematic review of this subject is available. The aims of this systematic review are to summarise and critically assess the evidence from randomised clinical trials (RCTs) for or against the effectiveness of maca in the improvement of sexual function, including sexual desire and sexual responses. Methods Page 2 of 6 that reported an RCT in which humans were treated with any type of maca (Lepidium meyenii) preparation, regardless of origin, were included. Trials were included if they employed maca as the sole treatment or as an adjunct to conventional treatments compared to a placebo control. Studies that used at least one measure related to sexual function were included. We excluded trials comparing two different types or dosages of maca and those in which no clinical data or insufficient data for comparison were reported. For duplicate publications with different outcome measures originating from one trial published as separate papers, the original publication was given priority, and all others were excluded. No language restrictions were imposed. Extraction of data and assessment of risk of bias All of the included articles were read in full. Three independent reviewers (BCS, MSL, and EJY) extracted the data, including methods (e.g., design, blinding, duration of follow-up), sample (e.g., population size, conditions, age, duration of disease), intervention and control treatment, and outcome measures, according to predetermined criteria (Table 1). The Cochrane classification (i.e., sequence generatio (...truncated)