Vegetarian Diet Patterns and Chronic Disease Risk

Vegetarianism continues to increase globally due, in part, to perceived health benefits. Results from observational studies indicate that vegetarian dietary patterns are associated with favorable cardiometabolic risk factor profiles and lower risks of chronic diseases including obesity, diabetes mellitus type 2, cardiovascular disease, and cancer. Aside from avoidance of meat and the compensatory dietary alterations, vegetarians tend to practice lifestyle habits conducive to better health. Well-controlled intervention trials show minimal or no effects of lean meat intake on traditional markers for chronic disease risk, although biologically plausible mechanisms exist through which consumption of meat and other animal products could influence risks of cardiovascular disease and some cancers. Thus, at present, the degree to which favorable health outcomes associated with vegetarian diet patterns are attributable to avoidance of animal products per se is unclear. This issue has major public health implications because more than 95% of the US population are regular consumers of meat and other animal products. This review aims to summarize the evidence regarding vegetarian diet patterns and major chronic diseases, explore possible explanations for these relationships, and identify research gaps and opportunities to better define the health effects of vegetarian dietary patterns. Nutr Today. 2019;54(4):132Y140 Vegetarian diet patterns are characterized by avoidance of meats, poultry, and fish/seafood and are mainly plant based, although several variations are practiced (Table 1). The most commonly practiced form is the lacto-ovo vegetarian pattern in which the individual avoids consumption of meats (eg, beef, pork, veal, lamb, mutton), poultry (eg, chicken, turkey), and fish/seafood, but does consume dairy products and eggs. Vegan dietary patterns avoid all animal products, and intermediate patterns include semivegetarian (also known as flexitarian) and pescovegetarian (includes fish and/or other seafood). Most people in the United States are omnivores who consume meats and other animal products. Surveys and polls have shown prevalence of 1.4% to 3.3% for vegetarian diets in the United States, including a prevalence of veganism of approximately 0.5%. People choose vegetarian dietary patterns for a variety of reasons. In the National Health Interview Survey in the United States (2012), approximately 2% of the population reported having followed a vegetarian diet pattern within the last 12 months for health reasons, and lifetime history of doing so was 4%. Other reasons for choosing vegetarian diets include religious beliefs, as well as concerns regarding animal welfare and the environmental impact of animal food production. Many who choose a vegetarian dietary pattern have a mix of these motivations. The 2015Y2020 Dietary Guidelines for Americans (DGA) include a Healthy Vegetarian eating pattern (modeled as a lacto-ovo vegetarian diet), along with Healthy American and Healthy Mediterranean-style eating patterns as examples that can be adapted to promote health and reduce chronic disease risk according to cultural andpersonal preferences. Most recently, the EAT-Lancet Commission released its report aimed at achieving healthy diets from sustainable food systems by 2050 because food is ‘‘the single strongest lever to optimize human health and environmental sustainability on Earth. ’’ Primary recommendations of the report were to decrease red meat and added sugars, particularly among wealthier nations, by more than 50% and to double the intake of fruits, vegetables, legumes, and nuts to benefit human health and provide a foundation for environmental sustainability. This equates to target intakes of 14 g/d of meat (beef, lamb, and pork), 29 g/d poultry, 13 g/d egg (56 g/d of combined meat, poultry, and eggs), and 28 g/d of fish. The 2015 DGA’s standard 1.5 CPEUs and 1.5 ANCC Contact Hours