Excerpts from our conversation with Dr. Kenneth Wright, Jr., an NIH-funded expert on sleep at the University of Colorado, Boulder.
NIHNiH: What is the circadian system? And why is it disrupted by shift work, such as working the night shift?
Wright: The circadian system is our biological clock. That biological clock controls the timing of a lot of our behaviors. These include when you choose to eat and when you choose to be active. For humans, our bodies are programmed to eat food during the daytime, not at nighttime, and be physically active during the daytime and not at nighttime.
For example, look at a hormone called melatonin. Our clock tells the body when to produce melatonin. And high levels of melatonin signal our biological night. Humans are not meant to be eating when melatonin levels are high….