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Title: Glycaemic potency of breakfast and cognitive function in adolescent schoolchildren
Author: Micha, Erini
ISNI:       0000 0004 2675 5970
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2008
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The aim of the present PhD was to assess how the glycaemic potency of breakfast affects cognitive function (CF) in adolescent children; using CF tests which have previously been shown to be sensitive to variations in circulating blood glucose (BG) levels; and timing the CF tests appropriately to the physiological properties of the breakfast under study. Three studies were conducted in order to test this; a cross-sectional study in children (A), a clinical study in young adults (B), and an intervention study in children (C). (A): Sixty children aged 11-14 years were selected on the basis of being regular breakfast caters. Their breakfast on the morning of the study was recorded. They were then categorized into four groups according to the glycacmic index (GI) and glycaemic load (GL) of the breakfast; low GI - high GL, high GI - high GL, low GI - low GL and high GI - low GL above or below the median for GI=60.6 and GL=27.5. Consumption of a low GI - high GL breakfast was associated with better performance on a majority of the tests 90-120 minutes later, suggesting a possible role for the glycacmic potency in CF. (B): In order to test meals that were different in their GI and GL in an intervention setting, we would have to ensure that the meals selected differed in their glycaemic and insulinacmic responses The meals were based on what the children reported eating in the cross-sectional study. Therefore, the aim of the clinical study was to measure the postprandial glycaemic and insulinaemic responses of breakfast meals differing in their GI and GL over a period of three hours after the ingestion of the meals( every 15 min during the first hour, and then ever 30 min); to measure cortisol levels over the same period; and to investigate the validity of the methods for calculating GI and GL. Ten young adults (5 males, 5 females) took part. The breakfast meals were administered in a cross-over design, and differed in their GI and GL: a low GI - high GL (1), a high - GI high GL (2a) of similar GL to (1), a high GI - high GL (2b) of similar energy and macronutrient composition to (1), a low GI - low GL (3) and a high GI - low GL (4). Insulin and glucose responses differed significantly between the high and the low GL meals, while the picture is less clear for the high and low GI meals. The iAUC (incremental area under the curve) at 120 min was predicted in a linear fashion by the calculated GL. There were no differences with regard to cortisol responses. (C): The four breakfast meals( 1,2b, 3,4) were administered in 74 children. The children were matched based on gender, form, age, height and BMI. Each child and their match were randomly assigned to the low or the high GL breakfast. Within each GL group, children were given high or low GI breakfasts. Mood, salivary cortisol (SC) and BG levels were measured The low GI - high GL meal was associated with improved mood and satiating effects. When taking mood, BG and SC levels into account, the low GI meals predicted better performance on a verbal fluency task, and the high GI meals on vigilance tasks. The assumption that could be made is that the GI effects are domain specific: a low GI meal, and as a result of that lower BG levels, could result in lower activation of the HPA-axis (hypothalamic pituitary adrenal) under demanding situations (lower SC levels and feeling less `nervous'), and therefore better declarative memory performance. Conversely, a high GI meal, and as a result of that higher BG levels, could result in stronger activation of the HPA-axis under demanding situations (higher SC levels and feeling more 'nervous'), and therefore better vigilance.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available