Comparison of diet quality of US adults based on primary motivation for following a vegetarian diet: A cross-sectional online study

Abstract

Adults adopt a vegetarian diet for various motivations, but it is unknown their overall diet quality based on a primary motivation. The purpose of the study was to compare overall diet quality, nutrient intake and related food groups based on primary motivation for following a vegetarian diet. It was hypothesized that vegetarians who chose the diet for health-related motivations would have a higher diet quality based on the Healthy Eating Index (HEI)-2015 scores compared to those following the diet for other motivations. A cross-sectional study was conducted online in the United States. Participants (n = 511) completed an 18-item questionnaire and a 24-hour recall using the Automated Self-Administered 24-hour Dietary Recall (ASA24-2018) and were divided into one of three groups (Health, Animal, Other [family, religious beliefs, or environment]) based on their primary motivation for following a vegetarian diet. Total HEI-2015 scores were determined and Kruskal-Wallis ANOVA on Ranks with a Dunn's Method for all pairwise comparisons (p < 0.05) were conducted. Results showed that total HEI-2015 scores differed among groups (p = 0.022) with the Health group having a higher score than the Other group (70.2 [57.0, 79.1] versus 63.6 [52.2, 77.1], median 25th, 75th) but not the animal rights group (66.5 [55.1, 77.0]). Higher component scores for total protein foods, seafood and plant proteins and fatty acids contributed to the significant difference. Adults who were motivated by health to follow a vegetarian diet had a higher diet quality than those who cited Other as their primary motivation. As motivations may impact diet quality of vegetarians, it is necessary to account for them.

Introduction

Consuming a vegetarian diet is a growing trend within industrialized countries [1], [2], [3]. A vegetarian diet is the exclusion of meat, fish and poultry, but can vary from including animal by-products such as eggs and/or dairy (i.e., ovo and/or lacto vegetarian) or may restrict all animal by-products such as honey (i.e., vegan) [4]. Animal rights/ethics, environmental sustainability and health are the main nonreligious motivations behind the adoption of vegetarian diet [1,[5], [6], [7]]. A study [1] was conducted to identify the top three motivations for following a vegan diet among German consumers (n = 329). Results showed that most participants listed at least two motivations for adopting this diet. Ninety percent of participants indicated that one of the motivations was related to animal rights. Forty-seven percent listed environmental protection and 70% listed personal well-being or health as the motivation for following a vegan diet. The animal rights/ethics motivation is based on protecting the welfare of animals [1]. Environmental motivations relate to reducing environmental degradation and greenhouse emissions as fewer resources such as fertilizers, water and land are needed to produce plant foods for human consumption compared to foods for animal consumption [8,9]. Motivations related to health may be based on data showing stronger associations between the vegetarian dietary pattern and a lower body mass index (BMI) than an omnivorous dietary pattern [10,11] as well as reduced risk for developing chronic diseases (e.g., cardiovascular, type 2 diabetes and prostate cancer) [12], [13], [14], [15], [16], [17].

A 2018 Gallup poll revealed that out of 1,033 American adults who participated in the poll, 5% considered themselves vegetarians and 3% considered themselves vegans, which was essentially unchanged from a 2012 survey [18]. Common demographic characteristics of adults who adopt the vegetarian diet are females, college-educated, non-Hispanic whites and ‘other’ races/ethnicities that are not Hispanic and African-American [2,7,18,19]. Although there are some data that describe the demographic characteristics of those who follow a vegetarian diet based on motivations [1,19], little is known about diet quality related to motivation.

Researchers [6] used a food frequency questionnaire to compare dietary intake for those who followed a vegan diet for health reasons to those who followed it for ethical reasons. Data showed that those who followed a vegan diet for health reasons ate more fruit and less sweets than those who followed the diet for ethical reasons. Another study [20] determined dietary intake of adults based on motivations (i.e., religious, animal rights and health) for following a vegan diet and showed that those who were motivated to follow a vegan diet for animal rights ate more high fat products. Neither of these studies, though, determined if certain motivations for consuming a vegetarian diet led to a lower or higher diet quality. One method to assess diet quality is through the Healthy Eating Index (HEI)-2015. The HEI-2015 determines the degree a dietary pattern adheres to the Dietary Guidelines for Americans using a scoring system [21]. A study assessed the diet quality of vegan, vegetarian, and omnivorous diets using the HEI-2010, however, information about primary motivations for following these diets was not collected [10].

In the current cross-sectional online study, the tested hypothesis was vegetarians who chose the diet for health-related motivations would have a higher diet quality based on the HEI-2015 scores compared to those following the diet for other motivations. The specific objective of this study was to compare the overall diet quality, nutrient intake and related food groups based on primary motivations for following a vegetarian diet among US adults. For the purposes of this study, the term vegetarian will be used to describe those who identify as lacto/ovo vegetarians or vegans.