Abstract/Summary

Enhancing diet quality remains a critical public health priority due to its significant impact on cardiometabolic disease (CMD) development and 40% of the deaths globally attributed to unhealthy dietary habits. The APOLIPOPROTEIN (APO)E gene plays a critical role in lipid metabolism, and its genetic variants, particularly the APOE E4 allele, have been associated in some studies with an increased risk of cardiovascular disease (CVD) compared to the wild-type E3/E3 homozygotes. This PhD project aimed to explore the association between adherence to higher-quality diets, assessed through established and novel diet quality scores (DQS), as well as empirically derived dietary patterns, and risk factors for CMD in disease-free UK adults. Furthermore, investigations into how the APOE genotype interacted with diet quality to influence CMD risk markers was completed. A scoping review using a systematic approach was undertaken (Chapter-2) to determine commonly used DQS to assess the association between diet quality and CMD risk markers in healthy adults. Healthy Eating Index-2010 (HEI), Alternate HEI-2010, modified Mediterranean Diet Score, alternate Mediterranean Diet Score (aMED), and Dietary approach to stop hypertension score (DASH) were identified as commonly used DQS from the 47 studies described in the 57 publications identified. It was hypothesised (Chapter 3) that a novel UK specific DQS (eNutri) would be more superior than the HEI-2015, aMED, and DASH score in determining the relationship between diet quality and CMD risk. While the eNutri-DQS showed similar associations with anthropometrics, blood lipids, and diastolic blood pressure (DBP) as the other scores, it emerged as the only DQS associated with the arterial stiffness index (digital volume pulse). Additionally, the DASH score was the only DQS that was inversely associated with total cholesterol and low-density lipoprotein cholesterol. Using principal component analysis two main dietary patterns (DP) were identified (Chapter 4), explaining 11.7% of the total variance of food intake among UK adults. DP1 rich in fermented dairy, wholegrains, fruits, and vegetables, and lower intakes of red and processed meat products was associated with lower body mass index, waist circumference, triacylglycerol and DBP, as well as higher high-density lipoprotein cholesterol (HDL-C). DP2 characterised by high consumption of sugars and refined grains, was associated with lower HDL-C. Finally, in Chapter 5, the role of APOE genotype on the relationship between eNutri-DQS and CMD risk factors was determined. Compared to wild-type E3/E3 group, higher diet quality was associated with lower central adiposity, favourable body fat distribution, and lower fasting glucose (E4 only) in E2 and E4 carriers. To conclude, higher diet quality and greater adherence to DP1, broadly aligned with UK dietary guidelines, may be associated with a more favourable cardiometabolic health profile in UK adults. The eNutri-DQS emerged as a useful tool for evaluating the relationship between diet quality in future CMD risk, with a potential role of APOE genotype on this relationship.