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Neuroscientists discover why food tastes better when hungry


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OKAZAKI, Aichi Prefecture–Researchers identified bodily mechanisms that make even unappetizing meals seem scrumptiously delicious during hunger pangs.

Kenichiro Nakajima, an associate professor of neuroscience at the National Institute for Physiological Sciences here, and his colleagues studied the brains of mice and located nerve systems that change the sense of taste among those with empty stomachs.

“Mechanisms may have been developed and maintained in the process of evolution to change the palate and allow starving animals to consume food that has gone bad to some extent, thereby taking in energy efficiently,” Nakajima said.

According to the scientists, when people are hungry, food tastes different and the stuff they like to eat changes. But why that happens has been unknown.

To unravel the mystery, the team surveyed how AgRP neurons in the core part of the brain become activated to stimulate appetite when the stomach is empty.

The researchers applied light to the cerebral nerves of mice to artificially make them famished and examined the effects of the neurons on gustation, the action of tasting. Mice are said to have a sense of taste similar to that of humans.

When the mice were fed a sucrose solution, the hungry ones were twice more likely to lick the liquid in 10 seconds than their non-treated counterparts, although the solution’s sweetness level was only one-third that of cola.

The results also showed the hungry mice licked the artificially developed bitter substance twice more frequently than untreated mice, showing that hunger makes the animals less sensitive to otherwise unfavorable flavors.

After repeating the experiment, the team discovered that the AgRP neurons linked to the lateral septal nucleus and the lateral habenular nucleus in the brain adjust how mice taste food.

While the lateral septal nucleus is known as the central nervous system associated with feelings of anxiety, the lateral habenular nucleus is believed to be connected to a sense of hatred.

The researchers said when the functions of the nuclei are inhibited in starving mice, the lateral septal nucleus makes them more attached to sweetness while the lateral habenular nucleus urges them not to shy away from bitterness.

Nakajima said the research could also shed light on obesity.

“Obese people tend to like sweet stuff, and examining the effects of obesity on nerve systems may help identify what is behind that tendency,” he said.

The team’s findings were published in the online edition of the British scientific journal Nature Communications on Oct. 8.

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