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This is Scientific American's 60-Second Science. I am Cynthia Graber. This will just take a minute.

Brains can register a food’s caloric value independent of our taste buds, say scientists from Duke University and from Portugal. First the scientists engineered mice without taste receptors for sweets. They compared the so-called sweet-blind mice to normal mice. Both were offered plain water or water with sucrose. And within about ten minutes, even the sweet-blind mice preferred the sugar water. The same test was repeated with sucrose, a calorie-free sweetener. The mice that could taste the sweetener preferred it, but the mice without the taste receptors never developed a preference for the fake stuff. Then the researchers looked at the brains of the sweet-blind mice. Sucrose turned on neurons in the brain’s food reward system. And the brain chemical dopamine was elevated. Dopamine is a crucial part of the brain’s reward circuitry. These changes show that the brain’s reward system can detect internal physiological¹ changes even independent of taste, maybe through the digestive system. The work appears in the March 27 issue of the journal Neuron. Scientists are calling this nutrient² awareness³ the brain’s sixth sense for calories. They say teasing out these mechanisms⁴ could have implications in understanding and combating obesity⁵.

Thanks for the minute for Scientific American's 60-Second Science. I'm Cynthia Graber.