As is customary at this time of year, bellies up and down the US will be going into overdrive this Thanksgiving, sending a tsunami of food comas rippling across the nation. While most people assume that this intense post-meal fatigue is caused by the diversion of blood away from the brain and towards the gut, scientists have actually never come up with any hard evidence to explain the food coma phenomenon – until now.
A new study in the journal eLife describes how researchers observed the sleep patterns of fruit flies after eating. Interestingly, they found that only certain types of food caused them to become drowsy, with salt and protein sending them to sleep for a period of up to 40 minutes, while sugar had no such effect.
The team then observed the flies’ brain activity as they ate, and found that the introduction of protein activated neurons in their leucokinin receptors, causing them to go to sleep. Leucokinin is a neurotransmitter that has previously been found to regulate fruit flies’ food intake, and is the equivalent of a substance called tachykinin in vertebrates.
When the researchers genetically silenced these leucokinin receptor neurons, the flies no longer became sleepy after eating proteins. In a statement, study co-author Keith Murphy explained that “by turning on and off neurons in the fly brain, we identified several circuits dedicated to controlling postprandial sleep.”
Despite these revelations regarding the mechanisms that control food comas, many questions remain unanswered as to why sleeping after eating is necessary. In the wild, sleep increases animals’ vulnerability, and is therefore only worth it if it brings considerable benefits.
The team therefore speculate that slumbering may aid digestion, or could help to consolidate memories about the location of food sources, although more much more research will be needed before the mystery of the food coma is fully solved.