Vegetarian and vegan diets in type 2 diabetes management Neal D Barnard, Heather I Katcher, David JA Jenkins, Joshua Cohen, and Gabrielle Turner-McGrievy Vegetarian and vegan diets offer significant benefits for diabetes management. In observational studies, individuals following vegetarian diets are about half as likely to develop diabetes, compared with non-vegetarians. In clinical trials in individuals with type 2 diabetes, low-fat vegan diets improve glycemic control to a greater extent than conventional diabetes diets. Although this effect is primarily attributable to greater weight loss, evidence also suggests that reduced intake of saturated fats and high-glycemic-index foods, increased intake of dietary fiber and vegetable protein, reduced intramyocellular lipid concentrations, and decreased iron stores mediate the influence of plant-based diets on glycemia. Vegetarian and vegan diets also improve plasma lipid concentrations and have been shown to reverse atherosclerosis progression. In clinical studies, the reported acceptability of vegetarian and vegan diets is comparable to other therapeutic regimens. The presently available literature indicates that vegetarian and vegan diets present potential advantages for the management of type 2 diabetes. © 2009 International Life Sciences Institute INTRODUCTION Diabetes has reached epidemic proportions, with an esti- mated 180 million cases worldwide. 1 Dietary factors and obesity play major roles in the risk of developing type 2 diabetes, and nutritional changes are a key aspect of disease management. 2 Current dietary approaches for managing type 2 dia- betes typically call for limiting carbohydrate intake, lim- iting intake of saturated and trans fats and cholesterol, and reducing energy intake in overweight individuals. 2 These guidelines are individualized based on medical condition, lifestyle, and food preferences. 3 However, evi- dence from observational and clinical studies suggests that plant-based diets offer specific advantages. In ran- domized trials, vegetarian and low-fat vegan diets have been shown to improve glycemic control, blood lipid concentrations, and body weight, in some instances to a greater extent than is achieved with more conventional dietary guidelines. 4 This review summarizes observational and interven- tion studies on the effect of vegetarian diets on type 2 diabetes. LITERATURE SEARCH METHOD A Medline (National Library of Medicine, Bethesda, MD) search was conducted for scientific articles containing information on vegetarian diets and diabetes using the key words “vegetarian” or “vegan” and “diabetes”, with the search limited to studies of adult humans published in the English language since 1966. Additional reports were identified from the references listed in these articles and from personal communications. Two reviewers (NDB and HIK) judged the eligibility of the studies independently. These searches yielded 116 potentially relevant articles, of which 10 were directly related to glycemic control and diabetes management. Additional articles reported findings on other clinically Affiliations: ND Barnard and J Cohen are with the Department of Medicine, George Washington University School of Medicine, Washington, DC, USA. ND Barnard and HI Katcher are with the Washington Center for Clinical Research, Washington, DC, USA. DJA Jenkins is with the Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, and Clinical Nutrition and Risk Factor Modification Center, St. Michael’s Hospital, Toronto, Canada. G Turner-McGrievy is with the Department of Nutrition, School of Public Health, University of North Carolina, Chapel Hill, North Carolina, USA. Correspondence: ND Barnard, 5100 Wisconsin Ave., Suite 400, Washington, DC 20016, USA. E-mail: nbarnard@pcrm.org, Phone: +1-202-686-2210, ext. 303, Fax: +1-202-686-2216. Key words: diabetes, diet, plant-based, vegan, vegetarian Special Article doi:10.1111/j.1753-4887.2009.00198.x Nutrition Reviews® Vol. 67(5):255–263 255