Canadian Science Publishing sponsors the Applied Physiology, Nutrition, and Metabolism Undergraduate Research Excellence Awards, which are awarded in partnership with the Canadian Society for Exercise Physiology and the Canadian Nutrition Society. Award winner Jennifer Lee shares her research on carbohydrate consumption and cognition in children.
By Jennifer Lee
For the past two years, I had the pleasure of working under the mentorship of Dr. Nick Bellissimo, an Associate Professor in the School of Nutrition at Ryerson University. During this time, I ran research trials and managed Nutrition, Exercise and Testing (NExT) Lab, part of Nutrition Discovery Labs directed by Dr. Bellissimo. While expanding my nutrition and physiology knowledge and developing research skills, I lead a study titled The Effects of Potatoes and Other Carbohydrates on Cognitive Performance, Glycemic Response, Subjective Emotions and Satiety in Children.
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Why study carbohydrates?
Carbohydrates provide glucose for the body, which is important for metabolism, tissue function, and regulation of food intake. Regular glucose consumption is particularly important for the brain, because the brain has the greatest metabolic activity of any organ, has limited energy storage capacity, and uses glucose as its main energy source. The glucose enhancement theory hypothesizes that higher circulating blood glucose levels allow for greater passage of glucose to the brain. Could a short-term increase in blood glucose levels from carbohydrate consumption contribute to transient improvements in cognitive performance? The consumption of pure glucose has been found to improve some cognitive domains in adults, but improvements in cognitive performance have not been consistently observed after the consumption of different carbohydrate-containing foods. Because children’s brains use glucose at up to twice the rate of adults, carbohydrate-mediated changes in cognitive performance may be especially pronounced in children.
In children, carbohydrates have also been shown to suppress short-term subjective satiety and to lower food intake. The classical glucostatic theory of food intake control suggests that increases in blood glucose from meal ingestion lead to satiety and terminate eating. However, recent research has questioned this theory as carbohydrates producing both low and high glycemic responses (i.e., small and large food/meal-induced increases in blood glucose, respectively) have been shown to reduce subjective appetite. Could subjective satiety be influenced by glycemic responses specific to eating a particular type of carbohydrate?
A growing body of literature shows that white potatoes may have a stronger effect on subjective satiety than other carbohydrates in children. Yet, white potatoes, and their products, have been receiving a disproportionate amount of blame for contributing to the obesity epidemic. This is partly due to observational studies showing a positive association between potato consumption and obesity, highlighting the need for randomized trials.
Using a within-subjects repeated measures design, we assessed the short-term effects of consuming white potatoes and other carbohydrates on cognitive performance, glycemic response, subjective emotions, and satiety in children.
How did we conduct the research?
We recruited 22 children (7 girls and 15 boys) aged 9–14 years for the study. On six separate mornings at least one week apart, children came to our lab after a 12-hour fast. Upon arrival, an initial blood sample was taken to measure glucose, and subjective emotions and satiety were assessed with 100 mm long visual analogue scales (VAS); children were asked questions related to their subjective feelings and were instructed to place an ‘X’ along the VAS reflecting their feelings at the moment. Then, children consumed one of five carbohydrate types (mashed potatoes, fried French fries, hash browns, white rice, or white beans) or continued to fast (control). Cognitive performance tests, glycemic response, and subjective emotions and satiety were assessed throughout a 180-minute period post-consumption (Fig.1).
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| Fig.1. Test-day protocol. |
We used several cognitive performance tests to assess five cognitive domains: verbal declarative memory (word-list recall), spatial memory (modified map task), short-term memory (forward digit recall), working memory (backward digit recall), and information processing speed (striking A’s).
Do carbohydrates affect cognitive performance and satiety?
Out of the five cognitive domains, only verbal declarative memory was affected by treatment. Children recalled more words after eating fried French fries, compared with when they ate mashed potatoes and white rice. Eating mashed potatoes resulted in the lowest appetite scores. Glycemic response and subjective emotions did not influence cognitive performance or satiety.
What do these findings mean?
Our results support the evidence that white potato products have functional benefits in children through their effects on short-term cognitive performance and satiety in addition to providing essential nutrients. However, because of the wide variety of study designs used in the literature, it is challenging to compare and contrast our results with previous work. Consistent study design and standardized methodology will enable parents, teachers, healthcare professionals, and other public officials to effectively use information from nutritional research to better guide decision making, recommendations, and policies.
This is the first study to quantify and describe the effects of carbohydrate sources on cognitive performance and satiety in children. Because of this, our findings open the door to many more research questions, including:
- Besides blood glucose, what other physiological mechanisms can play a role in improving cognitive performance and suppressing satiety?
- Why was only one cognitive domain (verbal declarative memory) affected by treatments?
- What are the unique properties of fried French fries that resulted in improved cognitive performance and mashed potatoes on subjective satiety?
- What are the long-term effects of regular white potato consumption?
As we continue to move forward with these research questions, we get closer and closer to understanding the physiological effects of different foods and meals and how they affect our behaviours.
Jennifer Lee is in her final year of the Food and Nutrition program at Ryerson University. She completed her Honours Bachelor of Science degree in Biology and Psychology at McMaster University. Her previous research project looked at declining cognitive performance and sensory functions in mice with neurodegenerative disorders. She works as a research assistant and the lab manager at Nutrition and Exercise Testing (NExT) Lab. She is currently working on a study to understand the effects of potatoes and other carbohydrates consumed at breakfast on food intake, satiety, and glycemic response in children.
