A study published on March 22 in Cell has shed new light on the relationship between diet and sleep quality. The research indicates that a protein-rich diet decreases the arousability of both flies and mice, suggesting that dietary protein may play a role in promoting deeper sleep. The study’s authors, led by Iris Titos, a neuroscientist at Harvard Medical School, also identified the mechanism responsible for this effect in flies: dietary proteins activate gut cells that secrete a peptide, which in turn signals a group of neurons responsible for regulating the response to mechanical vibrations.
To explore this connection, the researchers began by analyzing the roles of approximately 3,400 fly genes, eventually identifying around 160 genes that contributed to hypo- or hyper-arousable flies. They then focused on a neuropeptide called CCHa1 and its receptor, which were among the genes of interest.
CCHa1 is synthesized in both the brain and the gut. When researchers depleted it from the brain and gut, they discovered that its elimination in the gut was sufficient to increase arousability in flies. The cells responsible for secreting CCHa1 in the gut are activated by dietary proteins and amino acids. The team found that a diet supplemented with a protein mix increased CCHa1 levels in the flies’ gut, making them less responsive to vibrations while they slept. In contrast, supplementation with sugar and fat did not produce the same effects.
Experiments conducted on mice revealed that a protein-enriched diet made these animals less responsive to mechanical vibrations as well, although the exact mechanism remains unclear. The team is now investigating whether the same molecules are involved in this process.
While the researchers describe the effect of protein intake and CCHa1 levels as promoting “deeper sleep” in these animal models, Bruno van Swinderen, a neuroscientist at the University of Queensland who was not involved in the study, cautions against using this term. He argues that while protein supplementation may increase the arousal threshold, this does not necessarily equate to deeper sleep or improved sleep quality. He emphasizes that deeper sleep involves specific functions that were not assessed in this study.
In response, Rogulja notes that increasing the arousal threshold is an important component of sleep regulation, and deep sleep requires the highest arousal threshold. She acknowledges that there are multiple aspects of deep sleep, but maintains that the arousal threshold is essential.
Van Swinderen acknowledges the study’s significance in terms of the gut-brain axis connection, stating that the findings reveal an interesting story about how diet can affect behavior, including arousal thresholds.