FIGURE 6 - uploaded by Sandra I Sünram-Lea
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2 The homeostatic control of blood glucose. Following a meal, glucose levels increase and high blood sugar levels (pink) stimulate the pancreatic islets of Langerhans beta cells to release insulin. Insulin lowers circulating glucose in two ways: it prevents the liver from releasing additional glucose and it promotes storage of glucose as glycogen or by conversion to fat by the liver and adipose cells and then stored in the adipocytes. As blood glucose levels decrease, the negative feedback of glucose causes beta cells to stop secreting insulin and the body's metabolism returns to basal state. Conversely, when blood glucose is low (blue), the secretion of the opposing pancreatic hormone glucagon is induced. Glucagon induces the breakdown of liver glycogen to glucose and increases gluconeogenesis in the liver. Gluconeogenesis is the biosynthesis of a carbohydrate from simpler, non-carbohydrate precursors such as pyruvate.
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There has been increasing interest in the effects of nutrition on cognitive performance and more specifically how cognitive performance can be optimised using nutritional interventions. The macronutrient glucose has particularly received attention and is perhaps most thoroughly researched in terms of its effects on cognition. The notion that oral g...
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... Glucose is the primary monosaccharide in mammalian metabolism and most abundant dietary sugar-accounting for ~80% of the end product of CHO digestion [4]. Glucose is virtually the sole fuel for the brain except during prolonged starvation when liver ketone bodies are oxidized. ...
This review examines the effects of carbohydrates, delivered individually and in combination with caffeine, on a range of cognitive domains and subjective mood. There is evidence for beneficial effects of glucose at a dose of 25 g on episodic memory, but exploration of dose effects has not been systematic and the effects on other cognitive domains is not known. Factors contributing to the differential sensitivity to glucose facilitation include age, task difficulty/demand, task domain, and glucoregulatory control. There is modest evidence to suggest modulating glycemic response may impact cognitive function. The evidence presented in this review identifies dose ranges of glucose and caffeine which improve cognition, but fails to find convincing consistent synergistic effects of combining caffeine and glucose. Whilst combining glucose and caffeine has been shown to facilitate cognitive performance and mood compared to placebo or glucose alone, the relative contribution of caffeine and glucose to the observed effects is difficult to ascertain, due to the paucity of studies that have appropriately compared the effects of these ingredients combined and in isolation. This review identifies a number of methodological challenges which need to be considered in the design of future hypothesis driven research in this area.
