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”If the brain is given the choice between pleasant
taste and no energy, or unpleasant taste and energy,
the brain picks energy” said Ivan de Araujo of the
John B. Pierce Laboratory and senior author of the
study "It turns out the brain actually has two
segregated sets of neurons to process sweetness and
energy signals".
Sugar’s sweetness and calorie content combine to
give it lethal power to destroy diets, many
scientists have assumed. However, new study by Yale
University researchers says the brain responds to
taste and calorie counts in fundamentally different
ways. And only one of these responses explains why
most New Years’ resolutions have already disappeared
under a deluge of Boston Crème Pies.
It’s the brain’s desire for calories — not sweetness
— that dominates our desire for sugars, according to
the study appearing Jan. 25 in the journal Nature
Neuroscience.
Both sweet taste and nutrient value register in the
striatum, an ancient region of the brain involved in
processing rewards. Humans have a sweet tooth as one
way to ensure we eat enough to give our large brains
enough calories to operate at peak efficiency.
However, the Yale team studying the brains of mice
showed that signals for taste and nutrients are
processed in two separate areas of the striatum, the
ventral and dorsal, respectively. Signals about the
value of taste are processed in the ventral striatum
while nutritional value was processed in the dorsal
striatum. The dorsal striatum remained responsive to
energy even when calories fed to mice were paired
with a very aversive taste.
The researchers then asked which signal had more
control over eating behavior. Mice fed both sugar
with sweet taste but no calories or sugar that
contained calories but was altered to taste horribly
preferred the sugar with energy. When neurons in
dorsal striatum were activated by light a technique
called optogenetics, mice also ate copious amounts
of bad-tasting sugar.
“The sugar-responsive circuitry in the brain is
therefore hardwired to prioritize calorie seeking
over taste quality,” de Iraujo said.
The authors hope findings help spur new strategies
aiming at curbing excess sugar intake.
Luis Tellez of Yale is lead author of the paper. The
National Institutes of Health funded the research.
For more information
nature neuroscience
Separate circuitries encode the hedonic and
nutritional values of sugar
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