Research reportInvestigation of lifestyle choices of individuals following a vegan diet for health and ethical reasons☆
Introduction
The proportion of Americans following a vegan diet has increased substantially in the past 15 years from approximately 300,000 to 500,000 people in 1997 to between 2.5 and 6 million in 2012 (1–2% of the U.S. population; Newport, 2012, Stahler, 2012). The number of vegans worldwide has yet to be established, although research indicates that this number is on the rise, especially in more affluent countries (Key, Appleby, & Rosell, 2006). For example, a recent survey in Israel reported that 5% of Israelis consumed a vegan diet (Aharoni, 2014). In a survey of 3618 individuals in the United Kingdom, 2% self-identified as vegan (Department for Environment, Food and Rural Affairs, 2007), while in another survey of Australians, 1% reported following a vegan diet (The Vegetarian/Vegan Society of Queensland Incorporated (VVSQ), 2013). In Germany there are 900,000 vegans, approximately 1% of the population (VEBU, 2014). Surprisingly, India, which has a large number of vegetarians (31%; Yadav & Kumar, 2006) has a relatively small number of vegans. Moreover, in early 2014, Google Trends reported the highest level of searches for the term ‘vegan’ (100 on scale of 0–100; Google Trends, 2014).
One reason for this interest in a vegan diet is its reported health benefits. There have been several studies documenting the nutritional and health status of vegans (Craig, 2009, Dwyer, 1988, Key et al, 2006). In a cross-sectional study, vegans were found to have an average body mass index (BMI) of 23.6 compared to non-vegans who had a mean BMI of 28.8 (Tonstad, Butler, Yan, & Fraser, 2009); a BMI of 22.5 to 25 is considered ideal (Mahan & Escott-Stump, 1999). Similarly, vegans are found to have lower cholesterol (Bradbury et al., 2013) and blood pressure (Pettersen, Anousheh, Fan, Jaceldo-Siegl, & Fraser, 2012), as well as reduced risk of cardiovascular disease (Spencer, Appleby, Davey, & Key, 2003) and diabetes (Tonstad, Stewart et al., 2013). Both vegan and vegetarian diets may lower the risk of certain cancers such as colon (Fraser, 1999), stomach (Key, Appleby, Spencer, Travis, Allen et al., 2009), female (Tantamango-Bartley, Jaceldo-Siegl, Fan, & Fraser, 2013), and prostate (Fraser, 1999) cancers. Risk of diverticular disease for vegans was only a quarter of that of omnivores (Crowe, Appleby, Allen, & Key, 2011) while risk for hypothyroidism was 10% lower than omnivore risk (Tonstad, Nathan, Oda, & Fraser, 2013). In the Adventist Health Study 2 (Orlich et al., 2013), the largest study of the health effects of vegetarian and vegan diets, the overall death rate for vegans was reduced 15%, which approached statistical significance. However, in other studies with smaller samples (e.g. Burr, Sweetnam, 1982, Key et al, 1998, Key et al, 2009) there was no survival advantage for those following a vegan diet. While reduced mortality has not yet been shown for the vegan diet, it is clear that substantial health benefits may accrue to those adhering to it.
Foods consumed on a vegan diet are diverse and not always healthful. They can include fruits, vegetables, legumes, nuts, seeds, healthy fats, and whole grains, with documented health advantages (Key et al, 2006, Spencer et al, 2003). At the same time, grain-based foods high in sugar, salt and unhealthy fats can be vegan. This raises the question of whether the health advantages of a vegan diet result from just avoiding animal products, or from an overall concern for health that includes choosing nutritious foods and engaging in other health-promoting behaviors. In fact, if choosing a vegan diet is linked to engaging in healthier behaviors overall, then these factors should be investigated and accounted for in future studies.
Other researchers have noted that people following a vegan diet may choose to do so for different reasons, which in turn, may affect their food and lifestyle choices (Dyett, Sabaté, Haddad, Rajaram, & Shavlik, 2013). These reasons include health, animal rights (ethics), environmental concern, influence of others, and sensory disgust, with health and ethical considerations emerging as the most often cited reasons. Both quantitative and qualitative research has shown that health and ethical reasons were most often cited for choosing to follow a vegan diet (Dyett et al, 2013, Ruby, 2012).
In the current study, our objective was to investigate reasons for choosing a vegan diet and associations with a wide range of health and lifestyle factors in a large international sample of individuals following a vegan diet. We hypothesized that those choosing a vegan diet for health reasons would be more likely to engage in other healthy behaviors, which could affect their health and nutritional status.
Section snippets
Participants
Participants were solicited through events targeting vegans (e.g. festivals and social gatherings) or through social media (e.g. Facebook groups). To be included, participants had to affirm that they were between the ages of 25 and 60, and that they consumed a strictly vegan diet as indicated by answering “none” to a multiple-choice question asking which animal foods they consumed at least monthly. Three hundred fourteen individuals began the survey, and 302 finished it, with complete data
Results
Data were analyzed using nonparametric statistical tests due to unequal sample sizes. Mann–Whitney U tests were conducted to compare those following a vegan diet for ethical (ETH) and health (HEA) reasons on diet duration, DASS-21 scores, BMI, exercise patterns, hours worked per week, hours spent outdoors per week, sleep, social support, alcohol intake, and food consumption patterns. Effect size was calculated for significant variables using Pearson's r.
Chi-square analyses were conducted to
Discussion
To summarize, compared to the HEA group, the ETH group reported being on a vegan diet longer, consuming greater quantities of soy, select foods high in vitamin D, sweets per day, select beverages high in polyphenols and vitamin supplements. Conversely, the HEA sample reported consuming significantly more select fruits and fruit juices high in polyphenols than did the ETH sample.
In our sample, the ETH participants had remained on the diet significantly longer than the HEA participants, a result
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Acknowledgements: The authors would like to acknowledge the assistance of Carol Burtnack, Maria DiNello, Michael Greenberg, Michelle Herrera, Cassandra Hoy, Tyler Loranger, Bret Moyer, Amy Rinne, Melissa Sharp, and Jessica Dalrymple.