The study, published in the journal Physiology & Behavior, suggests that eating sugar can negatively affect our cognitive abilities, particularly our attention.
Researchers examined the effects of different sugars—glucose, a simple sugar; fructose, which is commonly found in fruits and plants; and sucrose, most commonly known as table sugar—against a placebo sweetener, sucralose, which is an artificial sweetener. In a double-blind, placebo-controlled study, they tested subjects' cognitive abilities using three methods, asking them to do simple math, a timed-response task, and the classic Stroop test (in which color words like red are written in other colors, like blue, and subjects are asked about the color or the word).
Results indicated that thinking is adversely affected for those who consume glucose and sucrose, two sugars that cross the blood-brain barrier when digested. For those who fasted for 10 hours before the test, adverse effects were even stronger.
“Our study suggests that the ‘sugar coma’—with regards to glucose—is indeed a real phenomenon, where levels of attention seem to decline after consumption of glucose-containing sugar,” researcher Mei Peng of University of Otago in New Zealand told PsyPost regarding the study.
So it's glucose, not the perception of sweetness, glucose that determines whether or not you're likely to fall into a sugar coma.