Applied nutritional investigationVegetarianism and cardiometabolic disease risk factors: Differences between South Asian and US adults
Introduction
The prevalence of cardiometabolic diseases such as diabetes [1], [2] and coronary heart disease [3], [4] is increasing disproportionately in South Asia compared with other regions of the world [5], [6] despite high levels of vegetarianism [7]—a phenomenon referred to as the “South Asian paradox.” For example, the age-adjusted prevalence of diabetes among adults in India increased from 6.7% in 2006 to 9.3% in 2014 [8], [9]. In the United States, these numbers were 7.8% and 10.8%, respectively [8], [9]. Between 1990 and 2020, coronary heart disease is estimated to increase by 120% to 137% in developing countries compared with 30% to 60% in developed countries [6]. In India, between 2000 and 2030, an estimated 35% of all cardiovascular disease (CVD) deaths will occur among individuals ages 35 to 64 y, compared with only 12% in the United States [6].
The South Asian paradox may be explained by differences in the relative healthfulness of vegetarian versus non-vegetarian diets in South Asia compared with the United States and Europe [7]. Although several studies, including randomized controlled trials, have documented protective effects of vegetarian diets on cardiometabolic disease risk factors in US and European populations [10], [11], [12], few have evaluated these relationships in South Asian populations.
Two studies have explored these associations among South Asian immigrants to New Zealand and the United States: The first found vegetarians had, on average, a lower body mass index (BMI) and waist circumference compared with non-vegetarians but no difference in insulin resistance after adjustment for BMI [13]. The second study found lower insulin resistance among vegetarians than non-vegetarians but did not adjust for BMI [14]. The few studies conducted among South Asians living in South Asia reported mixed results: Some observed that vegetarians were less likely to be overweight [15], [16] and have diabetes [16], [17] compared with non-vegetarians; whereas others observed no difference in BMI [18], [19] but found that vegetarians exhibit lower levels of circulating lipids and blood pressure compared with non-vegetarians [18].
There is an even greater paucity of data comparing vegetarian diets in South Asia to other populations. Exploring intercountry differences is an important first step in identifying points of intervention to improve diet quality and prevent disease. Therefore, we assessed differences in food group intake of vegetarians versus non-vegetarians and quantified the association of vegetarian dietary patterns with overweight/obesity, central obesity, diabetes, hypertension, dyslipidemia, and a composite CVD risk score within urban South Asian (India and Pakistan) and national US samples.
Section snippets
Samples
We examined cross-sectional data on men and non-pregnant women (ages 20–69 y) in urban South Asia were from the baseline survey of the CARRS (Centre for Cardiometabolic Risk Reduction in South-Asia) cohort, conducted in three cities in 2010−2011: Chennai and New Delhi in India, and Karachi in Pakistan [20]. Cross-sectional data on men and non-pregnant women (ages 20–69 y) in the United States were from NHANES (National Health and Nutrition Examination Survey) 2003−2004 and 2005−2006, which
Results
One-third (33%; n = 4968) of adults in the South Asian sample were vegetarian. In contrast, only 2.4% (n = 59) of adults in the US sample were vegetarian, representing an approximate 14-fold difference in the prevalence of vegetarianism in South Asians versus Americans.
Among South Asian vegetarians, the most common form of vegetarianism was semi-vegetarianism (eat meat, poultry, and fish <1 time/wk): 40% of vegetarians followed this particular pattern (Table 1). Of the remaining patterns, 4% of
Discussion
The prevalence of any type of vegetarianism in this nationally representative US sample was substantially lower than that of the urban South Asian sample: 2.4% versus 33%. This proportion, defined objectively using food propensity data from the past year, is similar to the proportion of NHANES participants self-identifying as vegetarian in the 2007 to 2010 NHANES surveys. [34] A vegetarian diet was strongly associated with a lower probability of overweight/obesity and central obesity among US
Conclusion
There is greater divergence between vegetarian and non-vegetarian diets in the United States compared with South Asia, and US vegetarian diets have more consistently healthier food group intakes than South Asian vegetarian diets. Vegetarians had a lower probability and lower mean levels of several cardiometabolic disease risk factors in both South Asian and US populations. The strength of this cross-sectional association may be stronger for US vegetarian diets. Prospective studies are needed to
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The CARRS (Centre for Cardiometabolic Risk Reduction in South-Asia) cohort was funded by the National Heart, Lung, and Blood Institute at the National Institutes of Health (HHSN2682009900026C) and the Oxford Health Alliance Vision 2020 of the UnitedHealth Group (Minneapolis, MN). Additional support was provided by the Fogarty International Center and the Eunice Kennedy Shriver National Institute of Child Health & Human Development at the National Institutes of Health (1 D43 HD065249), and the Emory Global Health Institute. None of the aforementioned funding sources had a role in the design, analysis, or writing of this article. All authors were involved in the conception and development of the research plan (study question and analysis). L.M.J. conducted the statistical analysis and wrote the manuscript. All other authors contributed to editing and revising the manuscript. L.M.J. has primary responsibility for final content. All authors read and approved the final manuscript. The authors have no conflicts of interest to declare.