The role of dietary supplements in inflammatory bowel disease: a systematic review Roberta E. Rossi a , Tara Whyand b , Charles D. Murray c , Mark I. Hamilton c , Dario Conte a and Martyn E. Caplin c Inflammatory bowel diseases (IBD) are chronic immune disorders of unclear aetiology. Dietary deficiencies may be a potential pathogenic factor in their development. Patients often take food supplements without knowledge of any evidence base. We have therefore assessed the evidence for food supplementation in the management of IBD. A PubMed search was performed for the terms Inflammatory bowel disease; nutritional deficiencies; dietary supplements; curcumin; green tea; vitamin D/other vitamins; folic acid; iron; zinc; probiotics; andrographis paniculata; and boswellia serrate. PubMed was used to search for all relevant articles published between January 1975 and September 2015. Curcumin supplementation has been reported to be effective in reducing the symptoms and the inflammatory indices in IBD patients. Similar results have been observed for green tea; however, pertinent studies are limited. Vitamin D supplementation may help to increase bone mineral density in IBD patients and to reduce disease activity. IBD patients with ileal resections higher than 20 cm may develop vitamin B 12 deficiency that requires parenteral supplementation. There is no current evidence to support fat-soluble vitamin supplementation in IBD patients. Zinc and iron should be supplemented in selected cases. Probiotics (VSL#3) may reduce disease activity in IBD patients with pouchitis. Complementary and alternative medicines are used by IBD patients and some studies have shown promising results. In summary, attention to dietary factors such as curcumin, green tea and vitamins, including vitamins D and B 12 , appears to be beneficial and, if necessary, supplementation may be appropriate. Eur J Gastroenterol Hepatol 28:1357–1364 Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. Introduction Inflammatory bowel disease (IBD) is a heterogeneous group of chronic immune disorders of unclear aetiology, which mainly includes Crohn’s disease (CD) and ulcerative colitis (UC), the former involving any part of the gastro- intestinal tract and the latter involving only the large intestine. The pathogenesis of IBD is complex and involves genetic and environmental factors. A number of environ- mental risk factors have been explored, including smoking, appendectomy, oral contraceptives, diet, breastfeeding, infections/vaccinations, antibiotics and childhood hygiene; however, most of these factors have shown inconsistent findings so far. Notably, diet has been implicated as a potential pathogenic factor. The ‘Western diet’ (i.e. pro- cessed and highly refined sugars and fats) has been con- sidered to be partially responsible for the increasing incidence of IBD [1–3]. In patients with IBD, both defi- ciencies of macronutrients and, more often, deficits of specific micronutrients have been described. The main symptoms during flare-ups of IBD are diar- rhoea, abdominal pain and possibly weight loss. Such flares are generally managed by anti-inflammatory drugs, for example, the 5-aminosalicylic (5-ASA) class, immuno- suppressants (such as steroids, azathioprine, cyclosporine and methotrexate) and antitumour necrosis factor (TNF) agents. Recently, probiotics have been used particularly for the subset of patients with pouchitis. The high cost and the rate of adverse effects associated with drugs and frequent relapse have promoted the use of alternative options and many patients will take supplements of their own accord without any evidence base. On the basis of the above considerations, the present review was aimed at elucidating the possible role of food supplements in the management of IBD, focusing both on supplementation of patients who show nutritional defi- ciencies and on the administration of pharmacological doses of food supplements with potential therapeutic effects. Methods A bibliographical search was performed in PubMed for the Mesh terms inflammatory bowel disease; nutritional defi- ciencies; diet; dietary supplements; curcumin; green tea; vitamin D; folic acid; iron; zinc; probiotics; andrographis paniculata; and boswellia serrate and free text searches (alternative and complementary medicine). PubMed was used to search for all relevant articles published from January 1975 to September 2015. Reference lists from studies selected by the electronic search were searched manually to identify further relevant reports. Reference lists from all available review articles, primary studies and a Gastroenterology and Endoscopy Unit-Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Milan, Italy, b Department of Nutrition & Dietetics, Centre of Gastroenterology and c Centre for Gastroenterology, Royal Free Hospital, London, UK Correspondence to Martyn E. Caplin, BSc Hons, DM, FRCP, Centre for Gastroenterology, Royal Free Hospital, NW3 2QG London, UK Tel: + 44 207 830 2867; fax: + 44 207 472 6728; e-mail: m.caplin@ucl.ac.uk Received 12 April 2016 Accepted 13 July 2016 European Journal of Gastroenterology & Hepatology 2016, 28:1357–1364 Keywords: dietary supplements, inflammatory bowel disease, nutritional deficiencies ’ Review article 0954-691X Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/MEG.0000000000000728 1357 Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.