All living things keep time. Hummingbirds, for instance, keep track of the time it takes for different flowers to recharge their nectar, and fly around to them exactly when they are full. Likewise, we keep time, too, and not just by the watches on our wrists.
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Scientists have known about circadian rhythm, or the internal 24-hour clock, in plants for several hundred years. But it was only 25 years ago that the genetic mechanism behind our own circadian rhythm became apparent.
Every cell in every organ of our body can essentially tell the time. For instance, our body knows that 30 minutes after we eat, our liver must jump into action, and then the adrenal glands and kidneys, while our fat cells begin to absorb energy at a certain schedule, and so on. All the while, the master clock, our brain – like the conductor of an orchestra – keeps all the organs in sync by sending neuro-chemical signals at regular intervals.
Since our circadian rhythm plays a role in virtually all our body functions, it can be very difficult to change it. It’s why people who work the night or graveyard shift find that their work wreaks havoc on their sleep cycles and metabolism.
According to a 2018 study in the Switzerland-based journal Current Sleep Medicine Reports, light and darkness are vital cues for our body, so when our brain realises it’s night time, it releases the sleep hormone melatonin from the pineal gland, and slows down other processes, literally getting us ready for bed. So, when night shift workers work on their computers, do physical tasks or have a meal instead, the body’s natural rhythms get completely disrupted.
Interfering with our circadian clock can also have more serious implications. Epidemiologic studies show that related disruptions are associated with increased cancer risk, including cancers of the prostate, breast, colon, liver, ovary and lungs.