The delivery rate of dietary carbohydrates affects cognitive performance in both rats and humans

Glucose is the main metabolic fuel of the brain. The rate of glucose delivery from food to the bloodstream depends on the nature of carbohydrates in the diet, which can be summarized as the glycaemic index (GI).

To assess the benefit of a low versus high GI breakfast on cognitive performances within the following 4 h.

The influence of the GI of the breakfast on verbal memory of young adults was measured throughout the morning in parallel to the assessment of blood glucose levels. The learning abilities of rats performing an operant-conditioning test 3 h after a breakfast-like meal of various GI was also examined.

A low GI rather than high GI diet improved memory in humans, especially in the late morning (150 and 210 min after breakfast). Similarly, rats displayed better learning performance 180 min after they were fed with a low rather than high GI diet.

Although performances appeared to be only remotely related to blood glucose, our data provide evidence that a low GI breakfast allows better cognitive performances later in the morning.