Applied nutritional investigationUrbanized South Asians' susceptibility to coronary heart disease: The high-heat food preparation hypothesis
Introduction
The susceptibility to coronary heart disease (CHD) of urbanized South Asians remains incompletely explained [1], [2] (South Asians refers to people from the Indian Subcontinent especially India, Pakistan, Bangladesh, Sri Lanka, including those living overseas). For example, there was 62% increased mortality from ischemic heart disease among Pakistani-born men compared with the population of England and Wales [3]. Such high mortality reflects high incidence, not high case fatality [4]. The susceptibility of urbanized South Asians to CHD is international [3], [5], [6], [7], [8], [9], [10], [11].
This susceptibility has been linked to diabetes and metabolic syndrome. The insulin resistance hypothesis [11], however, does not explain the higher CHD risk in South Asians compared with white Europeans [2]. New ideas include the adipose tissue compartment hypothesis [12], the mitochondrial efficiency hypothesis [13], and the variable disease selection hypothesis [14], [15]. These augment the longstanding thrifty genotype and thrifty phenotype hypotheses [16], [17]. (A short account of these hypotheses can be found in online Supplementary Data.) Collectively, these evolutionary and developmental hypotheses have not yet explained the problem.
Unhealthy diets are important in CHD [18], [19], [20] and the type of food and its preparation might matter. We have, therefore, formulated the high-heat food preparation hypothesis. This is a cultural, rather than evolutionary, hypothesis and moves in a new direction. High-heat cooking promotes neo-formed contaminants (NFCs) such as trans-fatty acids (TFAs) and advanced glycation end-products (AGEs) [21], [22], [23], [24]. The present study compares the potential for producing NFCs in South Asian cuisine with Chinese cuisine, as the Chinese do not have special susceptibility to CHD, whether in China or overseas [25]. The search strategy used for this study is presented in Box 1.
Section snippets
Neo-formed contaminants and CHD: Human and animal evidence
We prioritized human studies [26], [27] despite their limitations, given our focus on the South Asian ethnic group, and NFCs in human foods. Limitations included that food intake data, usually based on a 3-day record or memory based-recall [28], do not equate to long-term exposure. Also, AGE levels from a food database may not always be the same as the food actually consumed by those surveyed. Nonetheless, evidence that NFCs influence human CHD is strong enough to underpin our hypothesis.
Animal
Evidence for the high-heat food preparation hypothesis: Indian and Chinese cuisines
If NFCs in food produced during cooking increase South Asians' susceptibility to CHD, they should be both comparatively high in diets and body tissues and associated with CHD in South Asians. Our literature searches yielded no data on this. Therefore, we have supported our hypothesis on indirect observations we compiled on cuisine and cooking methods (Table 1, Table 2, Table 3) and recently published empirical data on oils and TFAs (Table 4) [73]. The data on Indian and Chinese cuisines in
Testing the high-heat food preparation hypothesis
Our hypothesis, outlined in Figure 3, proposes that high-heat food preparation is a potentially important risk factor for South Asians. Despite searching for evidence carefully (Box 1), at this point, our hypothesis can only be supported indirectly, as no direct, comparative studies of either NFCs in South Asian cuisine, body or plasma NFC burdens, or on the relationship between NFCs and the relevant disease outcomes in South Asians were found. We recommend ways of testing the hypothesis,
Acknowledgments
The authors acknowledge Antonis Vlassopoulos for providing helpful guidance and suggestions to improve the quality of this study; Fu-Shing Lee for providing insight into Chinese cuisine; and Anne Houghton for providing secretarial support.
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2019, AtherosclerosisCitation Excerpt :Frequent intake of sugar-rich snacks and drinks may also play a role, at least in some SA subgroups [44,45]. Other features proposed as potentially relevant to SAs’ cardiovascular risk include additional dietary factors, such as intake of foods rich in saturated/trans fats (e.g., ghee, a type of clarified butter, although this practice is lessening in many SA communities) [27,39,40], high-heat food preparation [46], and reutilisation of cooking oil [46]; atherogenic dyslipidaemia, with low levels of high density lipoprotein cholesterol, hypertriglyceridemia, and small dense low density lipoprotein particles [3,7,13,19,27,30,36,47]; high levels of lipoprotein [a] [7,27,48]; obesity, particularly among women [18,49]; pro-thrombotic/pro-inflammatory states [7,27,36,48]; endothelial dysfunction [27,48]; and social factors, including low birth weight [50] and migration-associated stress; among others (Fig. 3) [27,30,48,51,52]. Importantly, none of these factors is directly captured in usual risk scores [1,13], and to what extent any of these, either in isolation or collectively, help explain the excess risk in SAs is currently not fully established, and future collaborative efforts are needed to examine these issues.
Epidemiology and determinants of type 2 diabetes in south Asia
2018, The Lancet Diabetes and EndocrinologyCitation Excerpt :Common examples include desi ghee (clarified butter), coconut oil (a saturated fat), partially hydrogenated vegetable oils containing trans fats (eg, vanaspati, which also contains high saturated fat palm oil), and dairy sources (also saturated fat). A major issue relates to the common practice of repeated or prolonged heating and reheating of cooking oil and the potential conversion of healthier unsaturated fatty acids to trans fats.107,120,121 Asian diets are also characterised by a high omega-6 and low omega-3 fatty acid ratio, which is implicated in the increased risk of cardiovascular disease and diabetes.121
Funding for this study was largely from authors' employing organizations; however, SK was funded by the charitable Cardiovascular Disease Research Fund at the University of Edinburgh (administered by RSB). RSB conceived the high-heat food preparation hypothesis. RSB and SK led on AGEs, and SB and AM on TFAs. SK led on successive drafts with intellectual contributions from all others. All authors have read and approved the final manuscript. The authors have no conflicts of interest to declare.