'Food coma' effect? Protein, salt promote post-meal sleep, study finds

Meals with higher protein and salt content could lead to longer naps. (g-stockstudio / istockphoto.com)

A study, published in the journal eLife, has investigated how what we eat can affect post-meal sleepiness and nap length. The researchers, based in the U.S., found that meals high in protein and salt could promote sleep and lead to longer naps.

According to researchers at the Scripps Research Institute in the U.S., what we eat influences post-meal sleep and its duration.

After testing the consumption of salt, sugar and protein in fruit flies -- insects used for their genetic similarities with humans -- the scientists found that meals with higher levels of protein and salt could promote sleep and lead to longer naps.

They identified a certain type of neuron -- called leucokinin neurons -- that play a role in the post-meal sleep mechanism. "A subset of leucokinin receptor (Lkr) neurons was necessary to initiate post-meal sleep in the presence of protein specifically," explains first author Keith Murphy.

"While we expected that flies defective in protein sensing would experience post-meal sleep in a similar way to those fed only sucrose, we found instead that they had a waking response. Our analysis suggests that ingested protein promotes both sleep and wakefulness, and that the wakefulness is counterbalanced by Lkr neuronal activity. "

The research provides a starting point for future work investigating the genes and circuits that link meal size, protein and salt to post-meal sleep.