ORIGINAL CONTRIBUTION Coffee and caffeine intake and risk of endometriosis: a meta-analysis Francesca Chiaffarino • Francesca Bravi • Sonia Cipriani • Fabio Parazzini • Elena Ricci • Paola Vigano ` • Carlo La Vecchia Received: 14 June 2013 / Accepted: 17 January 2014 / Published online: 31 January 2014 Ó Springer-Verlag Berlin Heidelberg 2014 Abstract Purpose The potential association between endometriosis and coffee/caffeine consumption has been analysed in several epidemiological studies. In order to establish whether caffeine influences the risk of endometriosis, we provide to summarize the evidence from published studies on this issue. Methods We performed a meta-analysis of epidemiolog- ical studies published up to January 2013. We computed summary relative risks (RR) of endometriosis for any, high and low versus no coffee/caffeine consumption. Results We identified a total eight studies, six case– control and two cohort studies, including a total of 1,407 women with endometriosis. The summary RR for any versus non-consumption were 1.26 [95 % confidence interval (CI) 0.95–1.66] for caffeine and 1.13 (95 % CI 0.46–2.76) for coffee consumption; the overall estimate was 1.18 (95 % CI 0.92–1.49). The summary RR were 1.09 (95 % CI 0.84–1.42) and 1.09 (95 % CI 0.89–1.33) for high and low caffeine consumption as compared to no consumption, respectively. Conclusion The present meta-analysis provided no evi- dence for an association between coffee/caffeine con- sumption and the risk of endometriosis. Coffee/caffeine consumption, as currently used in diet, does not carry a health risk. Keywords Epidemiology Á Coffee/caffeine intake Á Meta- analysis Á Clinical epidemiology Á Gender medicine Á Women’s health Introduction Endometriosis is a common gynaecological condition affecting 6–10 % of childbearing-age women and is asso- ciated with pelvic pain, dyspareunia and infertility [1]. Endometriosis may be related to genetic and environmental factors [2]. Several epidemiological studies have addressed the association between endometriosis and socio-demo- graphic factors, menstrual and reproductive factors [3] but potential modifiable risk factors are still to be identified. Caffeine is probably the most frequently ingested pharmacologically active substance in the world, and because of its wide consumption, its potential effects on human health have been a focus of concern. In women, caffeine has been suggested to act on hepatic production of sex hormone-binding globulin (SHBG) and subsequent reduction in bioavailable testosterone [4, 5]. Other studies hypothesize a role of caffeine in inhibiting aromatase, the key enzyme mediating the conversion of androgens to estrogens. However, results related to SHBG and hormone measurements were not consistent among various obser- vational and cross-sectional studies [6]. Still, any possible F. Chiaffarino Á S. Cipriani Á F. Parazzini (&) Á E. Ricci Department of Obstetrics, Gynecology and Neonatology, IRCSS Fondazione Ca’ Granda, Ospedale Maggiore Policlinico, Milan, Italy e-mail: fabio.parazzini@marionegri.it F. Bravi Á S. Cipriani Á F. Parazzini Á C. La Vecchia IRCCS ‘‘Mario Negri’’ Institute for Pharmacological Research, Milan, Italy F. Bravi Á C. La Vecchia Department of Clinical Medicine and Community Health, University of Milan, Milan, Italy P. Vigano ` Obstetrics and Gynecology Unit, San Raffaele Scientific Institute, Milan, Italy 123 Eur J Nutr (2014) 53:1573–1579 DOI 10.1007/s00394-014-0662-7