“The mouth is a more capable sensory organ than we currently
appreciate, able to distinguish carbohydrates from artificial
sweeteners when both taste identical,” said Dr. Nicholas Gant from
the Sport and Exercise Science department at the University of
Auckland’s Centre for Brain Research.
“Carbohydrates are extremely powerful stimuli that have profound and
immediate effects on the brain and the systems it controls,” said
Gant, the study’s senior author, in an email.
A sixth sense in the mouth for carbohydrates could explain why
athletes respond immediately to carbs, as well as some aspects of
uncontrolled eating disorders, Gant’s team writes in the journal
Appetite. It could also open avenues for food engineering Gant told
Scientists already knew that carbohydrate mouth rinses increased
activity in certain brain regions, and some studies have shown that
swishing a carbohydrate solution in the mouth and spitting it out
improves performance during strenuous exercise.
Gant and his team used special brain imaging, called functional MRI,
to look at the effects of three different mouth rinses used before a
simple exercise task performed by 10 study subjects.
They compared a sweet carbohydrate solution to a sweet solution that
didn’t contain carbs and a third solution that was not sweet and did
not contain carbs.
When the participants swished the sweet carbohydrate solution in
their mouths, there was greater activation in brain regions
associated with sensation and muscle performance than with either
the sweet solution without carbs or the tasteless solution without
The sweet carbohydrate solution also produced greater activation in
brain regions that control vision and in regions associated with
The fact that the other solutions didn’t have the same effect
indicates that we are able to detect carbohydrates in the mouth as a
separate sense from sweetness, according to the researchers.
“This ‘sixth taste sense’ for carbohydrate is likely one of many
additional food qualities that are detectable by receptors in the
mouth,” Gant said. “It’s becoming evident that the brain knows far
more about the foods we ingest that just our perception of taste.”
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“Both test solutions used in our study were sweetened artificially,
so the increased activation we observe is likely part of the ‘kick’
people complain is absent in diet beverages/products,” Dr. Gant
said. “We may be able to use our experimental platform to help
develop functional foods and artificial sweeteners that are almost
as hedonistically rewarding as the real thing (sugar).”
It’s also been suggested, Gant pointed out, that a failure in
signaling between the mouth and the brain is part of the problem in
some eating disorders that cause frantic eating behavior.
Gant added that the study’s findings might have implications for
athletes. They could explain why athletes suddenly “perk up”
immediately after drinking a carbohydrate solution, even before the
carbs have time to get absorbed by the body and converted to energy.
Whether carbohydrate mouth rinses can make better athletes remains
to be seen. "For endurance exercise these findings should be applied
cautiously," Gant said. The signals from the mouth send a message to
the brain and body that energy is coming, indicating “help is on the
way,” which may allow a depleted body to keep going, he said.
“But if nutrients aren't swallowed, and don't arrive in the
bloodstream,” Gant said, “the brain may be writing checks that the
body can't cash later in the race!"
SOURCE: http://bit.ly/1nNFLA0 Appetite, online May 21, 2014.
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