A high-protein diet may promote deeper sleep, according to a study that found mice and flies that eat more protein are less likely to wake up from movement-related disturbances.
When you go to sleep you stop consciously perceiving the world, including things that may disrupt sleep, says Dragana Rogulja at Harvard University. “We wanted to understand how it is that you can suppress sensory arousal.”
She and her colleagues assessed how 3400 genes influence sleep in fruit flies. Working with groups of eight flies, they silenced each of these genes in isolation, for a total of 27,200 gene-edited flies. The researchers monitored the flies as they slept on platforms atop loudspeakers, which intermittently produced vibrations.
Low-frequency vibrations woke up about 85 per cent of the flies that had one of two genes silenced: the first governs the production of a chemical messenger known as CCHa1, which regulates circadian behaviour, and the other governs the receptor for CCHa1. Both genes are expressed in the nervous system and the gut.
Removing these genes from the gut alone was enough to make the insects more likely to wake up during vibrations. Further analysis found that certain cells in the gut produce CCHa1 when exposed to proteins. CCHa1 then travels from the gut to the brain where it suppresses arousal during sleep.
Taken together, these finding suggest that protein plays a role in preventing arousal during sleep. To confirm this, the team fed flies either a high-protein diet or a regular diet for one day. Half as many flies on the high-protein diet woke up in response to vibrations as flies on a regular diet. A similar experiment in mice produced comparable results.
“The general idea makes sense. We sleep when our other needs are taken care of,” says Rafael Pelayo at Stanford University in California. “So, if you have some better-quality food, in this sense a protein-rich diet, then that would make you sleep deeper. At least it did in flies and mice. This may not apply to humans.”
The findings also only apply to mechanical stimuli like shaking. The genetic alterations didn’t change how easily animals awoke to other disturbances like heat or sound, meaning many other pathways control arousal during sleep as well, says Rogulja.