1 Thus, to date, evidence on the effect of sugar on brain function has been contradictory. In their recent systematic review of interventional studies, van de Rest et al 1 described inconsistent effects of glucose ingestion on mood, but information on cognitive performance was not presented. In contrast, a comprehensive research review performed in 2011 by Smith et al 19 described an enhancement of human memory after glucose ingestion in interventional studies. Beilharz et al 18 reported that the intake of refined sugars was associated with impaired memory tasks in both prospective cohort and cross-sectional studies. 17Ī few previous reviews have analyzed the effect of glucose on different aspects of brain functioning. 16 However, intake of total sugars, added sugars, sucrose, and added fructose has been inversely associated with cognitive performance. In contrast, a beneficial effect of glucose loads on cognitive function, particularly episodic memory, was suggested. Similarly, a report of Ochoa et al 15 showed that glucose and fructose, but not starch, were able to increase basal cerebral glucose metabolism in reward-related brain regions such as the anterior and dorsolateral prefrontal cortex and the orbitofrontal cortex, among others. Kenny 14 reported that sugar activates the same brain pathways as cocaine or other addictive drugs. The debate about the role of sugar in brain performance continues, and some works have described deleterious effects of sugar on cognition. 11 Recent research has also shown that weight loss resulting from a Mediterranean dietary pattern, which is characterized by a high intake of complex carbohydrates but a low intake of sucrose, 12 can improve cognitive performance in people with obesity. 10 It is well established that obesity and its comorbidities are associated with impaired cognitive performance, accelerated cognitive decline, and neurodegenerative pathologies. 9 The biggest drawback of high-glucose intake, however, is the increased risk of chronic diseases, including obesity, fatty liver, dyslipidemia, type 2 diabetes, and cardiovascular disorders, which may develop independently of body weight or energy intake. 7, 8 More recently, it has been suggested that sugar-containing drinks can have an adverse impact on children’s cognition, while fruit consumption can lead to an improvement in cognition. On the other hand, chronic excessive consumption of sugar is known to contribute to cognitive and memory deficits and to increase the risk of psychiatric disorders in younger populations, 6 an effect also described in observational studies in adults. This response may be attributable to increased absorption of glucose in the brain. 3, 4 The brain is sensitive to short-term drops in blood glucose levels and seems to respond positively when blood glucose rises, especially when individuals perform more intense cognitive tasks. 1 It has been suggested that sucrose can have a direct effect on the brain through its glucose component, as well as a peripheral effect through its fructose component, 2 likely because this sugar is first metabolized by the liver before it can be utilized by the brain. Glucose levels can be increased by direct intake of either glucose, a monosaccharide sugar unit, or sucrose, a disaccharide sugar unit made of glucose and fructose and commonly known as table sugar. Glucose is the main source of energy for the human brain and plays an essential role in the modulation of cognitive processes. Cognition, executive functions, glucose, sucrose, sugar INTRODUCTION

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