Researchers at Kent State University explored the role of glucoregulation, or the body’s ability to regulate blood glucose, in our cognitive performance.
“There have been previous studies suggesting that glucoregulation determines how many carbohydrates a person might need in order to see these cognitive benefits,” said Jason Anderson, one of the researchers and co-authors of the study.
He presented the findings at Nutrition 2019, a conference organized by the American Society of Nutrition, in Baltimore earlier this week.
The team previously investigated how cognitive performance relates to levels of fasting glucose, so this time they investigated glycemic response after individuals had digested something. In this trial, they looked at carbohydrate-rich beverages, comparing apple juice and milk, as well as water as a non-carbohydrate control.
Forty-four healthy adults came for three morning sessions after having fasted overnight. They completed a battery of cognitive tests in this fasted state, and then had their blood drawn.
“One test may be pressing one button on the computer when you see a certain shape on a screen and refraining from pressing a button when you see a different shape, so it tests inhibitory control for example,” Anderson explained. “Some tests just involve pressing a button as fast as you can as soon as you see something on a screen.”
After the first test, they were randomly assigned a beverage (8 ounces of 2% milk, apple juice, or water), and completed the cognitive tests again at 30, 90, and 150 minutes after digestion. The researchers also drew blood samples at multiple times after digestion.
In the next two days, participants conducted the same tests but assigned a different drink. It was repeated until each participant has had each trial drink once.
“It turned out that contrary to what we were expecting, we didn’t see people perform better after drinking juice when they had a smaller glycemic response,” Anderson said. “But we did see differences between the milk and water conditions,” he added.
One interesting point that stood out the most was that for the people who had the largest glycemic responses to juice, performed significantly better at the cognitive tests 30 minutes after ingesting milk compared to when they ingested water or the fruit juice.
“The relationship also reversed at 150 minutes, probably when their glucose levels were going below baseline or back to baseline or so,” he added.
The researchers posited that fruit juice may increase plasma glucose beyond a range for optimal cognition. But overall, no significant differences were observed between all three beverage conditions. For future studies, an oral glucose tolerance tests should be used.
“If findings replicate, they will inform optimal timing for milk consumption to best facilitate cognition,” the researchers wrote.
The research project was funded by the National Dairy Council.