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The Neurobiology of the 'Food Coma'
11/17/2015 Jesse Jenkins
What causes the progression from holiday feasting to holiday snoozing? Researchers reveal the powerful role sugar plays in putting us into that slumberous post-meal state. Read more...
Many of us are quite familiar with the lethargic haze of postprandial somnolenceâ??better known as a â??food comaâ??â??that inevitably descends upon us after weâ??ve overindulged in the myriad dinner courses, wines, and desserts that typify the holiday season. Now researchers have shown that this common post-meal phenomenon may have an unexpected culprit: sugar.
Despite its reputation as a stimulant, a new study in The Journal of Neuroscience shows that glucose can trigger post-meal drowsiness by exciting sleep-promoting neurons located in brain regions of the hypothalamus known as the ventrolateral preoptic nucleus (VLPO) that are critical to sleep regulation.
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â??It is very common for us to feel very sleepy after a large meal, and this post-meal sleepiness may help be explained with the discovery of this mechanism,â?? said Christophe Varin, first author of the study. â??Until now the link has never been demonstrated, but here weâ??ve shown that glucose can directly promote the activity of sleep-promoting neurons and affect sleep regulation controlled by this important hypothalamic area of the brain.â??
Varinâ??s team injected glucose into VLPO brain regions of mice and found that the mice fell deep into non-rapid eye movement sleep (NREM sleep) much more quickly and for longer lengths of time than when injected with a glucose-free solution. The team next conducted brain-slice experiments to record neuron activity in the mice, revealing that heavier doses of glucose directly correlated to an increased firing rate of sleep-active VLPO neurons.
According to Varin, this glucose-induced excitation suggests that catabolism of glucose in neurons leads to inhibition of the brainâ??s ATP-sensitive potassium channels to facilitate sleep onset. The increased VLPO neuron activity could contribute to inhibition of other arousal areas of the brain as well.
â??We were surprised the effects were so great,â?? said Varin. â??We expected some more subtle effects, but from what we saw, this mechanism is probably quite a strong factor for sleep regulation.â??
For now, Varin believes the mechanismâ??s discovery could be helpful in explaining more than just the drowsiness one feels after a high-sugar meal. â??We are still trying to understand how food intake affects sleep and, conversely, how disturbed sleep can affect food intake as poor sleep quality is linked to increased obesity risk,â?? he said. â??This may help us further understand how metabolism is linked with sleep.â??
Varin C, Rancillac A, Geoffroy H, Arthaud S, Fort P, Gallopin T. Glucose Induces Slow-Wave Sleep by Exciting the Sleep-Promoting Neurons in the Ventrolateral Preoptic Nucleus: A New Link between Sleep and Metabolism. J Neurosci. 2015 Jul 8;35(27):9900-11.