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We Are Wired For Sugar
Norbert, when your tongue is enjoying your mouthful of ice cream, another body part may be tasting that tasty treat. When you say 'taste' what you really mean is 'sense'. There may be a whole other pathway to the brain toggling our sugar switch and it's in our gut. Scientists working with mice, found that when sugar enters the intestines, it binds to receptors that send signals up the vagal nerve to an area of the brain stem called cNST. The vagal nerve connects the gut to the brain. And only glucose triggers the signal, not other forms of sugar such as fructose in fruit or even artificial sweeteners. So, it's not the sugary taste that triggers the gut to brain pathway but the actual glucose molecule that the brain responds to. This makes sense since glucose is the building block of life.
Scientists in this study found that mice given sugar water and artificially sweetened water had at first liked both but quickly only drank from the sugar water. Then, when they bypassed the tongue and injected sugar into mice guts, the pathway was again stimulated. This study affirms the importance of glucose because this gut to brain pathway only activates the glucose-signaling after it's been ingested and absorbed. It also makes sure that animals identify, develop, and reinforce a strong preference for glucose containing foods. That explains why sugar substitutes have neither satisfied sugar cravings nor lowered sugar intake in America. Maybe this work will lead to healthier ways to satisfy our sugar cravings.
More Information
A gut instinct for glucose
All animals use sugar to produce energy, and so it is not surprising that they have evolved a preference for sugar over non-nutritional sweeteners. However, even animals that lack the sugar-sensitive taste receptors T1R2 and T1R3 develop a preference for sugar over sweeteners, suggesting that sugar preference can be mediated via means besides taste. Now, writing in Nature, Tan et al. characterize a gut'brain connection that is needed for sugar preference in mice...
A gut-to-brain circuit drives sugar preference and may explain sugar cravings
TA little extra sugar can make us crave just about anything, from cookies to condiments to coffee smothered in whipped cream. But its sweetness doesn't fully explain our desire. Instead, new research shows this magic molecule has a back channel to the brain...
The Gut-Brain Axis Mediates Sugar Preference
The taste of sugar is one of the most basic sensory percepts for humans and other animals. Remarkably, animals can develop a strong preference for sugar even if lacking sweet taste receptors, pointing to a mechanism independent of taste. Here we examined the neural basis for sugar preference and demonstrate that a population of neurons in the vagal ganglia and brainstem are activated via the gut-brain axis to create preference for sugar...
