Late-night eating and melatonin may impair insulin response

Posted on April 2nd 2019 (9 months)

The body's circadian rhythms – the 24-hour cycles of biological, hormonal, and behavioral patterns – are optimized to promote our survival. These rhythms modulate a wide array of physiological processes, including the body's production of hormones that regulate sleep, hunger, and metabolism, ultimately influencing body weight, performance, and susceptibility to disease. Roughly 10 to 40 percent of gene expression in mammals is under circadian control including genes in the brain, liver, and muscle[1][2]. As such, circadian rhythmicity may have profound implications for human healthspan.

A key player in the body's circadian metabolic processes is melatonin, a hormone produced deep within the center of the brain, in the pea-sized pineal gland. Melatonin plays an important role in our physiology by regulating the expression of more than 500 genes, but we rightly think of it as a sleep inducer with its increased production being tied to both our natural sleep time and our light exposure. In fact, the greatest influence on its secretion is light: generally, melatonin levels are low during the day and high during the night.

But melatonin doesn't regulate sleep alone. It sends messages to other parts of the body in preparation for sleep, including the pancreas, where it binds to receptors and signals the temporary (overnight) suppression of insulin production. This wasn't a problem in our pre-industrial past, but in today's environment of 24-hour food availability, it can have far-reaching effects on health. When food consumption regularly occurs outside normal daylight hours, the risk of hyperglycemia – higher than optimal blood glucose levels – increases. Chronic exposure to elevated glucose increases our risk of developing diabetes and other metabolic disorders. But it might also cause brain volume. Studies have shown in an association of even high normal fasting blood glucose associated with losses in the hippocampus and the amygdala, areas involved in memory and cognition. In other words, healthy people without diabetes.

Humans are the only species that disobeys their biological clocks, uncoupling the natural rhythms of light and dark around us. In this brief episode, we learn how restoring our dietary and sleep pattern to one that more closely syncs with those imposed by nature, especially by avoiding eating within 2-3 hours before bed and onset of melatonin production, may improve our health and potentially prolong our healthspan.

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