What's New

March 23, 2026 - Carbohydrate Nutrition News

Now Available: New Educational Resources about Sugars


October 16, 2025 - Carbohydrate Nutrition News

CNS Webinar Recording: Exploring the Links Between Sugars Intake and Diet Quality


Cognition

*This content has been reviewed by Dr. Krista Power (School of Nutrition Sciences, University of Ottawa); last updated May 2026

The term cognition refers to the mental skills we use to acquire, process, store, and transform information in daily life. Cognition includes skills like perception, attention, memory, executive functions (i.e. organization and planning, initiating tasks, and/or regulating emotions), and decision making.

  • Factors Affecting Cognition. Cognition covers a wide range of mental processes and tasks. The factors that affect cognition range from age and education to environmental factors and diet.
  • Carbohydrates and Cognition. The human brain uses a large amount of energy, and typically uses glucose as its sole source of energy for functioning. 
  • Sugars and Cognition. To date, there is some evidence to suggest that sugar may give a short-term energy boost to improve memory and focus, but consuming high amounts of sugars, especially from sugars-sweetened beverages (SSBs) may be linked to cognitive decline over time.  More rigorous research is needed to understand the long-term impact.

Factors Affecting Cognition 

There are several factors that can impact an individual’s cognition (1-5), including:

  • Age
  • Diet (e.g. alcohol, caffeine, antioxidants)
  • Education and socioeconomic status
  • Environmental factors (e.g. noise, lighting, temperature, crowding) 
  • Genetics
  • Physical activity
  • Smoking

Research has examined how diet affects cognition in both animal and human studies, and has looked at both cognitive performance as well as changes in brain chemistry in relation to cognitive functions. 

Carbohydrates and Cognition

The human brain uses a large amount of energy to function, and relies primarily on glucose as its main fuel source. Glucose is a component of sucrose (sugar). Glucose can be:

  • Derived from dietary carbohydrate, 
  • Synthesized in the body from other substrates such as amino acids, or 
  • Released from glycogen storage in the liver and muscles. 

When blood glucose levels are low, and the brain has less glucose available, it can adapt by using ketones, produced from the metabolism of fatty acids, as an alternative energy source.

Did you know? Despite making up only about 2% of an adult’s body weight, the brain consumes nearly 20% of the body's total energy, highlighting its high energy needs (6). The adult brain has a high and constant demand for glucose, consuming approximately 100 g per day or 55 mg per kg of brain tissue per minute (6-7).

The ketogenic diet (very low-carbohydrate, very high fat) has gained attention for its potential benefits in conditions like epilepsy (8). While some research suggests the ketogenic diet may improve cognitive function in certain populations, the evidence remains inconclusive due to small studies, reliance on animal models rather than human trials, and subjective testing methods (9-12). Unintended consequences such as kidney stones, high blood cholesterol levels, constiptation and nutrition imbalance exist for following the ketogeic diet for a long time. For these reasons, the ketogenic diet should be used with caution under the supervision of a health care professional. More rigorous studies are needed to better understand the effects of diet on cognition. 

Sugars and Cognition  

Glucose, a type of sugars, is the main fuel source for cells in the body, and is the primary source of energy for the brain (13). Specifically, the human body requires a minimum of 130 g of glucose per day (14), which is based on the amount the brain needs to function. 

The brain uses glucose from food or from stores in the body by breaking down carbohydrates (starches and sugars) into monosaccharides, such as glucose and fructose (as shown in the diagram below). Fructose is metabolized in the liver for energy or converted to glucose or lactate (13). 

The brain relies primarily on glucose to function.

Figure 1. The brain relies primarily on glucose to function. Restricting the brain's glucose supply can impair memory and ability to focus. 

Concerns have been raised about the effects of excess fructose intake on health, including cognition. Previous studies suggested that total energy intake confounded the relationship between fructose and congition, making it difficult to determine its direct impact (15-16).  

The consumption of sugars have different short (minutes to hours) and long-term (months and years) cognition-related outcomes.

  • Findings from experimental studies suggests that sugars have positive short-term effects on memory, word recall, attention, and learning processes in humans (17-18). 
  • In children, glucose has been shown to improve performance on complex mental tasks, such as verbal memory and remembering list items, compared to simpler tasks (14, 19-20). 
  • Over the long-term, observational studies have linked high intakes of added sugars - particularly SSBs - to an increased risk of memory decline, impaired decision-making and problem-solving, and higher risk of cognitive disorders like dementia and cognitive decline in middle-aged and older adults (17, 21-22). 
  • Research suggests that diets high in saturated fat and added sugars may harm the hippocampus, a brain region critical for memory and learning (23).

Current evidence suggests that reducing high intakes of added sugars, particularly from SSBs, may help support long-term cognitive function, but larger, well-controlled trials are needed to confirm these effects. 

For more information, additional resources include: 

Video - Sugar 101: Journey of a Sucrose molecule

References
  1. Deary IJ, Johnson W, and Houlihan LM. Genetic foundations of human intelligence. Hum Genet. 2009;126(1):215-32.
  2. Beydoun MA, Beydoun HA, Gamaldo AA, Teel A, Zonderman AB, Wang Y. Epidemiologic studies of modifiable factors associated with cognition and dementia: systematic review and meta-analysis. BMC Public Health. 2014;14(1): 643.
  3. Messier C. Glucose improvement of memory: a review. Eur J Pharmacol. 2004;90(1):33-57.
  4. Spoto, G., Di Rosa, G., & Nicotera, A. G. The Impact of Genetics on Cognition: Insights into Cognitive Disorders and Single Nucleotide Polymorphisms. J. Pers. Med. 2024;14(2): 156. 
  5. Kim, M., & Park, J. M. Factors affecting cognitive function according to gender in community-dwelling elderly individuals. Epidemiol Health. 2017; 39:e2017054. 
  6. Mergenthaler, P., Lindauer, U., Dienel, G. A., & Meisel, A. Sugar for the brain: the role of glucose in physiological and pathological brain function. Trends Neurosci. 2013;36(10):587–597. 
  7. Dienel G. A. Astrocytic energetics during excitatory neurotransmission: What are contributions of glutamate oxidation and glycolysis?. Neurochem Int. 2013;63(4):244–258. 
  8. Epilepsy Foundation. Ketogenic Diet. [Internet]. Epilepsy Foundation;2017 Oct 25 [cited 2025 Aug 29].
  9. Pavón, S., Lázaro, E., Martínez, O., Amayra, I., López-Paz, J. F., Caballero, P., Al-Rashaida, M., Luna, P. M., García, M., Pérez, M., Berrocoso, S., Rodríguez, A. A., & Pérez-Núñez, P. Ketogenic diet and cognition in neurological diseases: a systematic review. Nutr. Rev. 2021;79(7): 802–813. 
  10. Lima, M. C., Gabiatti, M. P., Moreira, J. D., Ribeiro, L. C., Lunardi, M. D. S., Lin, K., & Venske, D. K. Ketogenic diet, epilepsy and cognition: what do we know so far? A systematic review.  Nutr. Rev. 2022;80(10):2064–2075. 
  11. Chinna-Meyyappan, A., Gomes, F. A., Koning, E., Fabe, J., Breda, V., & Brietzke, E. Effects of the ketogenic diet on cognition: a systematic review. Nutr. Neurosci. 2023;26(12):1258–1278. 
  12. van Berkel AA, IJff DM, Verkuyl JM. Cognitive benefits of the ketogenic diet in patients with epilepsy: A systematic overview. Epilepsy Behav. 2018;87:69-77.
  13. Reichelt AC, Stoeckel LE, Reagan LP, Winstanley CA, Page KA. Dietary influences on cognition. Physiol Behav. 2018 Aug 1;192:118-26.
  14. European Food Information Council. Glucose and The Brain: Improving Mental Performance [Internet]. European Food Information Council;2018 Apr 30 [cited 2024 Mar 1].
  15. Lakhan SE, Kirchgessner A. The emerging role of dietary fructose in obesity and cognitive decline. Nutr J. 2013 Dec;12(1):114.
  16. Chiavaroli L, Ha V, de Souza RJ, Kendall CW, Sievenpiper JL. Fructose in obesity and cognitive decline: is it the fructose or the excess energy? Nutr J. 2014;13(1):27.
  17. Gillespie, K. M., White, M. J., Kemps, E., Moore, H., Dymond, A., & Bartlett, S. E. The Impact of Free and Added Sugars on Cognitive Function: A Systematic Review and Meta-Analysis. Nutrients. 2023;16(1):75. 
  18. García CR, Piernas C, Martínez-Rodríguez A, Hernández-Morante JJ. Effect of glucose and sucrose on cognition in healthy humans: a systematic review and meta-analysis of interventional studies. Nutr Rev. 2021 Jan 9;79(2):171-187.
  19. Bellisle F. Effects of diet on behaviour and cognition in children. Br J Nutr. 2004;92(S2):S227-32.
  20. Kennedy DO, Scholey AB. Glucose administration, heart rate and cognitive performance: effects of increasing mental effort. Psychopharmacology. 2000. 149(1):63-71.
  21. Liu, H., Liu, Y., Shi, M., Zhou, Y., Zhao, Y., & Xia, Y. Meta-analysis of sugar-sweetened beverage intake and the risk of cognitive disorders. J. Affect. Disord. 2022;313:177–185. 
  22. Zhang S, Xiao Y Cheng Y, Ma T, Liu J, Li C, Shang H. Associations of sugar intake, high-sugar dietary pattern, and the risk of dementia: a prospective cohort study of 210,832 participants. BMC Medicine. 2024;22(298). 
  23. Taylor ZB, Stevenson RJ, Ehrenfeld L, Francis HM. The impact of saturated fat, added sugar and their combination on human hippocampal integrity and function: A systematic review and meta-analysis. Neurosci Biobehav Rev. 2021 Nov;130:91-106.