Investigation into the dietary determinants of heart rate variability and potential mechanisms

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Heart rate variability (HRV), an indirect measure of cardiac autonomic function, is a powerful predictor of sudden cardiac death. Cardiac autonomic function is a neglected aspect of the pathophysiology of cardiovascular diseases (CVDs) in the field of nutritional sciences, with little published literature on effects of diet in this CVD risk factor. This thesis aimed at exploring the associations and impacts of some main dietary candidates that may influence HRV: long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) and energy intake restriction.
The first study compared HRV in vegans with omnivore controls, representing populations with low and high LC n-3 PUFA status, respectively. The observed differences between groups were more complex than hypothesised. Vegans presented higher 24 h overall HRV due to greater sleep-day differences compared to omnivores, and lower beat-to-beat HRV in the day-time. Vegans also presented lower availability of LC n-3 PUFA lipid mediators that may influence anti-inflammatory capacity, especially in populations with underlying chronic inflammation presenting low tissue LC n-3 PUFA status. This led to the next study, which characterised the variability of LC n-3 PUFA status in chronic kidney disease patients commencing haemodialysis, a population with high burden of inflammation and CVD compared to the general population, with the aim of establishing a potential relationship with HRV. Haemodialysis patients in this study had particularly low proportions and narrow degree of variability of erythrocyte membrane eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which precluded any meaningful findings in the relationship between tissue LC n-3 PUFA status and HRV. Finally, the last study compared the effects of intermittent and continuous energy restriction diets (IER vs. CER) on HRV in centrally obese, independent of weight loss. The results showed no superior effects of weight loss via an IER diet compared to a CER diet on HRV, and suggested that weight loss itself may have a much greater effect on HRV and other markers of cardio-metabolic risk than any independent effect of energy restriction type.
Date of Award2018
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorWendy Hall (Supervisor) & Thomas Sanders (Supervisor)

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