Imagine if by just changing around your diet you could have the ability to control your sleep cycle and the time of peak alertness. Japanese researchers, who published their findings in the journal Cell Reports, have shed some light on the quietly unknown world of sleep by manipulating sleep cycles through diet and food habits.
"Chronic desynchronization between physiological and environmental rhythms not only decreases physiological performance but also carries a significant risk of diverse disorders such as diabetes, cardiovascular diseases, sleep disorders, and cancer," the study’s co-author Dr. Makoto Akashi, Yamaguchi University, Japan, said in a press release.
Circadian rhythms are also known as the study of chronobiology. Each individual, regardless of age, has a specific chronotype, or internal timer, that is thought to be designed by our DNA and not by environmental factors. It is what is believed to determine whether a person is a morning person or a night owl. The neural and hormonal connection in the hypothalamus plays a key role in the intertwined relationship between sleep, food consumption, and the body’s natural clock.
Our internal clocks, which control sleep and wakefulness, can be traced down to a neurological level right inside our hypothalamus, a region in the brain where the neurotransmitter orexin, interacts with the stomach's ghrelin levels. Ghrelin activates orexin neurons located in the brain, which control sleep and appetite and therefore have the ability to enhance food consumption.
The orexin regulator may be beneficial for obesity, addiction, as well as sleep disorder treatments because of its inextricable control of sleep and appetite hormones. The hypothalamus is also where the optic nerve connects and communicates to the brain the level of light, or lack thereof, the eyes are exposed to throughout the day and night.
Located directly above the optic nerve is the suprachiasmatic nucleus (SCN), which controls circadian rhythms. Once the SCN is stimulated by the light transmitted through the eye, the message travels along the optic nerve, ultimately regulating neural and hormonal activity based on our personal circadian rhythms.
The relationship between circadian clocks and light response are clear; however, the clock’s response to food is much less understood, which is why Akashi and his colleagues experimented with mice cells. Researchers looked at their insulin, which is a pancreatic hormone secreted in response to feeding in order to control and filter sugar levels properly. They found insulin may be one of the key biological components to controlling the circadian clock.
"Insulin-mediated phase adjustment of the clock in feeding-relevant tissues may enable the synchronization between mealtime and tissue function, leading to effective digestion and absorption," Akashi said. "In short, insulin may help the stomach clock synchronize with mealtime."
Scientists have continually found a connection between lack of sleep and increased hunger and weight gain — and a recent study quantified the phenomenon. The findings were presented at the American Heart Association Annual Obesity Research Conference in 2012, which reported that otherwise healthy people may eat more than 500 additional calories when they’re sleep deprived.
According to data collected by the Centers for Disease Control and Prevention in 2011 from hospitals and health centers, 69.9 percent of men and 56.6 percent of women are either overweight or obese. The data is based on the universal body mass index scale, which categorizes individuals based on their height to weight ratio. Those with a BMI between 25 and 29 are considered overweight, and 30 or more obese.
Food and sleep may have a more intimate relationship than we initially thought. How deeply intertwined that relationship is, we aren’t sure yet. The findings notably suggest that manipulating the clock through diet may not work well for those who are insulin-resistant, such as those with type 2 diabetes. However, the new findings also provide new insights on insulin’s power to control the body’s sleep, wakefulness, and eating habits that we’ve never really understood before.
"For example, for jet lag, dinner should be enriched with ingredients promoting insulin secretion, which might lead to a phase advance of the circadian clock, whereas breakfast would be the opposite," Akashi said.
Source: Akashi M, Matsumura R, Node K, et al. The Role of the Endocrine System in Feeding-Induced Tissue-Specific Circadian Entrainment. Cell Reports. 2014.