One theory is that chewing increases arousal and leads to temporary improvements in blood flow to the brain.
The study carried out tests on volunteers while chewing or not chewing gum. The gum used was flavourless to avoid distractions, The Independent reported.
The brains of the men and women were also scanned with functional magnetic resonance imaging (fMRI) to see which areas were active.
The 30-minute tests involved volunteers pressing a button with their right or left thumb according to the direction of an arrow on a screen in front of them. One test was more complicated than the other. During both tests, alertness and reaction times were measured.
Results showed that alertness and reaction times improved while chewing gum. Men and women who were not chewing took 545 milliseconds to react, compared with 493 milliseconds among the chewers.
The scan results showed that the brain regions most active during chewing were those involved with movement and attention.
“Our results suggest that chewing induced an increase in the arousal level and alertness in addition to an effect on motor control and, as a consequence, these effects could lead to improvements in cognitive performance,” said the researchers from the National Institute of Radiological Sciences in Japan, and other centres.
Just how chewing could have such a profound effect is not clear, but there are theories. In one small experiment, chewing a piece of gum for 20 minutes led to an increased heart rate, and one suggestion is that this forces more oxygen and nutrients to the brain.
Another is that chewing leads to the production of higher levels of insulin, which stimulates areas of the brain concerned with memory and alertness.
“It is an interesting study. The improvement in reaction time they found is highly significant. It may be that the more complicated the task, the greater the effect on reaction times,” said Professor Andy Smith of Cardiff University, a leading health-related behavioural specialist who has investigated chewing gum and behaviour.
“We don’t really know how chewing could have such effects.
Is it simply the stress-relieving effect of the rhythmic action of chewing, like chanting or a squeeze ball, or is something more fundamental going on?” Smith said