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Sugar makes mice sleepy

Glucose injections trigger nerve cells to spur slumber

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6:00am, July 14, 2015
sugar data

SUGAR SHOCKER  In the two hours after an injection of glucose into the brain, mice fell into slow-wave sleep faster and stayed there longer (top) than mice injected with a non-sugar solution (bottom).

Contrary to parental belief, sugar may actually cause drowsiness, not hyperactivity. Key brain cells awash in glucose put mice to sleep, scientists report July 8 in the Journal of Neuroscience.

“We all experience this strong feeling of sleepiness after a very large meal,” says study coauthor Christophe Varin of Lyon Neuroscience Research Center and ESPCI ParisTech in France. Sugar is the reason those post-meal naps are often irresistible, the results suggest.

This study offers hard evidence that sugar promotes sleep, an idea that had been largely anecdotal, says neuroscientist Denis Burdakov of the Francis Crick Institute in London. “It’s really great to see it measured properly,” he says.

Varin and colleagues injected glucose directly into the brains of mice. Meals, particularly those loaded with carbs, raise sugar levels in the brain, too. This glucose might spur similar brain cells in people to exert sleepy effects.

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