Smith, Andrea Dominica; (2018) The aetiology of food and drink preferences, and relationships with adiposity. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Food preferences are important drivers of actual food choice, determining micro- and macronutrient intake; and poor dietary quality increases the risk for nutrition-related disease. Greater liking for sweets, fats and snacks has sometimes been related to higher body fat in childhood, yet the relationship in adults remains unclear. Twin studies are a powerful design to understand the importance of nature and nurture in these behaviours. So far, twin research on food preferences has only used young paediatric or adult populations but the relative importance of genes and the environment in shaping these preferences in early adulthood, a period of increasing independence and autonomous food selection, remains unknown. In addition, drink preferences have received little attention, and there is a need to find out if ‘unhealthy’ preferences are modifiable. This thesis uses data from TEDS, a large population-based cohort of 18-19 year old British twins, to assess the aetiology of food and drink preferences, and to investigate the association of food and drink preferences and adiposity, in late adolescence/early adulthood. Study 1 describes the development of a self-reported food and drink preference questionnaire, confirming that food preferences cluster in six traditional categories: vegetables, fruits, meat/fish, dairy, snacks and starches. Study 2 used the twin design to identify substantial genetic influences on preferences for six identified food categories and seven non-alcoholic drink types. In general, genetic effects were slightly higher for food than drink preferences, but the remaining inter-individual variation for all dietary preferences were influenced by non-shared environmental factors (any influences in the wider environment that make twins less similar despite their shared genes and home environment). Study 3a established that cross-sectional associations between dietary preferences and BMI are limited in this age group; only higher liking for dairy foods and non-nutritive sweetened beverages was positively associated with higher adiposity in older adolescents. Study 3b used a BMI-discordant MZ twin design to show that when genetic and shared-environmental confounding is eliminated, food and drink preferences do not explain adiposity differences in genetically-matched individuals. This design allowed to rule-out genetic or shared environmental factors as contributors to BMI-discordance. Lastly, Study 4 developed and piloted a short three-arm randomized controlled trial comparing two sugar reduction strategies (gradual vs. immediate cessation) to assess the feasibility of sweetness preference modification in relation to hot beverages, i.e. hot tea. Intake of sugar in tea decreased substantially in both sugar reduction conditions, without a loss in overall liking of tea. A better understanding of the aetiology of food and preferences, particularly identifying the importance of the wider environment as a salient shaper of both food and drink preferences, and their relationships with adiposity, has important implications for researchers, policy makers and clinicians. Establishing the feasibility of sweetness preference modification in beverages without loss of liking for the beverage is also important for public health initiatives, suggesting that such preference change is possible and likely sustainable over the long-term.

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