1.5 CPEUs and 1.5 ANCC Contact Hours Vegetarian Diet Patterns and Chronic Disease Risk What We Know and What We Don’t Orsolya M. Palacios, PhD, RD Kevin C. Maki, PhD, CLS Vegetarianism continues to increase globally due, in part, egetarian diet patterns are characterized by avoid- to perceived health benefits. Results from observational ance of meats, poultry, and fish/seafood and are studies indicate that vegetarian dietary patterns are asso- Vmainly plant based, although several variations are ciated with favorable cardiometabolic risk factor profiles practiced (Table 1). The most commonly practiced form is and lower risks of chronic diseases including obesity, dia- the lacto-ovo vegetarian pattern in which the individual betes mellitus type 2, cardiovascular disease, and cancer. avoids consumption of meats (eg, beef, pork, veal, lamb, Aside from avoidance of meat and the compensatory di- mutton), poultry (eg, chicken, turkey), and fish/seafood, etary alterations, vegetarians tend to practice lifestyle but does consume dairy products and eggs.1 Vegan dietary habits conducive to better health. Well-controlled inter- patterns avoid all animal products, and intermediate pat- vention trials show minimal or no effects of lean meat terns include semivegetarian (also known as flexitarian) intake on traditional markers for chronic disease risk, al- and pescovegetarian (includes fish and/or other seafood). though biologically plausible mechanisms exist through Most people in the United States are omnivores who which consumption of meat and other animal products consume meats and other animal products. Surveys and could influence risks of cardiovascular disease and some polls have shown prevalence of 1.4% to 3.3% for vege- cancers. Thus, at present, the degree to which favorable tarian diets in the United States, including a prevalence of health outcomes associated with vegetarian diet patterns veganism of approximately 0.5%.1 People choose vege- are attributable to avoidance of animal products per se is tarian dietary patterns for a variety of reasons. In the unclear. This issue has major public health implications National Health Interview Survey in the United States because more than 95% of the US population are regular (2012), approximately 2% of the population reported consumers of meat and other animal products. This review having followed a vegetarian diet pattern within the last aims to summarize the evidence regarding vegetarian 12 months for health reasons, and lifetime history of diet patterns and major chronic diseases, explore possi- doing so was 4%.2 Other reasons for choosing vegetarian ble explanations for these relationships, and identify diets include religious beliefs, as well as concerns re- research gaps and opportunities to better define the garding animal welfare and the environmental impact of health effects of vegetarian dietary patterns. Nutr Today. animal food production.3,4 Many who choose a vege- 2019;54(4):132Y140 tarian dietary pattern have a mix of these motivations. The 2015Y2020 Dietary Guidelines for Americans (DGA) include a Healthy Vegetarian eating pattern (modeled as Orsolya M. Palacios, PhD, RD, is a scientist in the Midwest Biomedical Research: Center for Metabolic and Cardiovascular Health, Addison, a lacto-ovo vegetarian diet), along with Healthy American Illinois. The main research focus is lifestyle and pharmaceutical ap- and Healthy Mediterranean-style eating patterns as ex- proaches to prevention and management of cardiometabolic diseases. amples that can be adapted to promote health and re- Kevin C. Maki, PhD, CLS, is the chief scientist in the Midwest Bio- duce chronic disease risk according to cultural and personal medical Research: Center for Metabolic and Cardiovascular Health, 5 Addison, Illinois. Dr Maki also holds an adjunct faculty position at DePaul preferences. Most recently, the EAT-Lancet Commission University, teaching biostatistics and applied epidemiology. The main released its report aimed at achieving healthy diets from research focus is lifestyle and pharmaceutical approaches to prevention sustainable food systems by 2050 because food is ‘‘the and management of cardiometabolic diseases. single strongest lever to optimize human health and en- During the time when this article was written, K.C.M. and O.M.P. received 6 support for research projects and/or consulting fees from the Alliance for vironmental sustainability on Earth.’’ Primary recommen- Potato Research and Education, the Almond Board of California, the dations of the report were to decrease red meat and added American Egg Board, Beef Checkoff, Coca-Cola, General Mills, Hass sugars, particularly among wealthier nations, by more than Avocado Board, Ingredion, Kellogg, and the National Dairy Council. 50% and to double the intake of fruits, vegetables, legumes, The authors have no conflicts of interest to disclose. and nuts to benefit human health and provide a foundation Correspondence: Kevin C. Maki, PhD, CLS, Midwest Biomedical Re- 6 search: Center for Metabolic and Cardiovascular Health, 211 E Lake St, for environmental sustainability. This equates to target Suite 3, Addison, IL 60101 ([email protected]). intakes of 14 g/d of meat (beef, lamb, and pork), 29 g/d Copyright * 2019 Wolters Kluwer Health, Inc. All rights reserved. poultry, 13 g/d egg (56 g/d of combined meat, poultry, DOI: 10.1097/NT.0000000000000350 and eggs), and 28 g/d of fish. The 2015 DGA’s standard \ 132 Nutrition Today Volume 54, Number 4, July/August 2019 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved. 1,3,8,9 TABLE 1 Different Types of Vegetarian and disease outcomes. Prospective cohort studies in the Nonvegetarian Dietary Patterns United States, the United Kingdom, Europe, and Australia have reported data on vegetarian dietary patterns and their Dietary Pattern associations with incidence of chronic diseases and/or Vegan Avoids consumption of all animal mortality.4,10,11 products Table 2 summarizes results from a meta-analysis of the incidence of various health outcomes published by Dinu Lacto-ovo vegetarian Avoids consumption of meats, 3 poultry, fish, and/or other seafood and colleagues. A total of 86 cross-sectional and 10 co- but consumes dairy products and hort prospective studies, which included a mix of popu- eggs; the most widely practiced form lation groups from the United States, the United Kingdom, of a vegetarian dietary pattern and Germany, were included in the analyses. In pooled Pescovegetarian Avoids consumption of meats and analyses, all disease outcomes investigated were numer- poultry, but consumes fish and/or ically lower among vegetarians and vegans compared with other seafood, and most often also omnivores, with relative risks indicating 2% to 25% lower consumes dairy products and/or eggs incidence. Among vegetarians, significantly lower inci- Semivegetarian Consumes small amounts of animal dence was present for ischemic heart disease (25% lower, (flexitarian) products, which may include dairy, P G .001) and all cancers (8% lower, P = .002). No statis- eggs, and/or seafood in a mostly tically significant differences were observed for all-cause plant-based diet (sometimes referred mortality, incidence of all cardiovascular disease (heart to as flexitarian) disease and stroke), breast cancer, or mortality from any Omnivore Consumes animal products, including cancer or specific cancer types (breast, colorectal, pros- meats, poultry, and seafood tate, lung). A much smaller sample was available to in- vestigate associations in vegans. In this group, incidence of all-cause mortality was lower by 12% (not statistically 2000-kcal healthy eating pattern model contains 105 g/d significant, P = .10), and all cancer incidence was signifi- of a combination of meat (beef, lamb, pork) poultry, and cantly lower by 15% (P = .006). Of note, subgroup analyses 5,6 Y eggs and 32 g/d of fish/seafood. Based on the 2011 indicate that a vegetarian diet was significantly associated 2012 National Health and Nutrition Examination Survey, with a lower risk of all-cause mortality and breast cancer Americans consume 72 g/d meat (eg, beef, lamb, and mortality in US Seventh Day Adventists with a shorter pork), 41 g/d poultry, 14 g/d eggs (102 g/d of combined (G14 years) follow-up; no significant associations were 7 meat, poultry, and eggs), and 19 g/d of fish. Although the found when assessing non-Adventists living in European EAT report did not specifically advocate for a vegetarian countries.3 dietary pattern, the significant target reductions in daily animal protein servings and the recommendation to ‘‘avoid meat’’ are attempting to move the population toward veg- etarian and vegan dietary patterns. Vegetarian dietary patterns are asso- The aims of this review are to (1) summarize the evi- dence regarding the relationships of the main vegetarian ciated with favorable cardiometabolic diet patterns (lacto-ovo vegetarian and vegan) to risks of risk factor profiles and lower risks of major chronic diseases, (2) explore possible explanations for the observed associations, and (3) review research chronic disease, including obesity, gaps that will need to be investigated in order to better define the potential health effects of such dietary patterns. diabetes mellitus type 2, cardiovas- Although a focus of recent plant-based dietary recom- mendations has been environmental responsibility, this cular disease, and some cancers. article will focus only on the nutritional and health-related consequences of the dietary patterns,