Originally published October 21 2008
Human Brain Seeks Real Calories; Artificial Sweeteners May Cause Overeating
by David Gutierrez, staff writer
(NaturalNews) The brain responds to the caloric content of food, not just to its sweet flavor, according to a study conducted by researchers from Duke University Medical Center.
For the study, the researchers compared the reactions of normal mice and mice that had been bred to have no sense of taste. First, they fed both normal and taste-blind mice both normal water and a sugar (sucrose) solution. They found that while the normal mice immediately preferred the sweet solution, the taste-blind mice at first did not distinguish between the two. Eventually, however, even the taste-blind mice began to preferentially lick at the sugar solution.
In the next test, the researchers let both groups of mice choose between plain water and water artificially sweetened with zero-calorie sucralose. While the normal mice immediately preferred the artificially sweetened solution, the taste-blind mice never showed any preference.
Next the researchers implanted probes in the animals' brains to observe how the different solutions affected the secretion of dopamine, a neurotransmitter associated with the sensation of pleasure.
In the normal mice, two different regions of the brain released dopamine when either sucrose or sucralose was tasted: the nucleus accumbens (NAcc) of the ventral striatum and the orbitofrontal cortex (OFC). In the taste-blind mice, however, the OFC region never responded, and the NAcc region responded only to sucrose. This suggests that while the OFC region is activated by sweetness, and either sweetness or calories activate dopamine secretion from the NAcc region.
The new research suggests that the body is able to distinguish between truly sugary foods and those that only taste sweet. This may partially account for findings that people eating low-calorie foods can end up consuming more calories than people eating higher calorie foods, because the low calorie foods are not as effective at making the body feel full.
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