How is it that our bodies know to fall asleep and wake up at the same time everyday? The simple answer is light (or the absence of it). Daylight acts as an indicator to our eyes and brain of when to initiate or end the sleep-wake cycle. Light exposure in turn synchronizes our sleep schedule and brain; this biological cycle is referred to as circadian rhythm.
When we sleep or begin to feel sleepy, we close our eyes to block light from hitting the back layer of the eyeball called the retina. Within the retina, there are intrinsically photosensitive ganglion (IPRG) cells. These cells receive light input to begin the signaling process through the optic nerve, to the suprachiasmatic nucleus (SCN), then to the pineal gland. The pineal gland sits in the midline of the brain and contains pinealocytes, cells that secrete melatonin. Simply put, when it becomes dark, cells in the eyes tell the brain to begin producing melatonin and eventually fall asleep.
What is Melatonin?
Melatonin is a sleep-promoting hormone. Melatonin falls into the supplementary category, as it is produced naturally by pineal gland but is also available in synthetic forms such as gummies, pills, or liquids. Our bodies produce it in alignment with our sleep-wake cycle, meaning that it is normally secreted around nighttime and stops in the morning to return to wakefulness.
*Taking melatonin may interfere with the effects of some prescription drugs
*Melatonin is not strictly regulated by the U.S. Food and Drug Administration (FDA)
Uses of Melatonin
Melatonin may aid in a variety of sleep-related issues, some of which include:
Jet lag (Temporary condition in which internal clock is out of sync with environment due to traveling across multiple time zones)
Shift work sleep disorder ([SWSD] Disorder found in people who work very long shifts or night shifts that result in needing to sleep during daylight or inconsistent times)
Circadian rhythm regulation in blind people (If IPRG cells are damaged, then the brain can have difficulty taking in external lighting cues for when to produce melatonin and fall asleep)
Under typical circumstances, our bodies produce enough melatonin on their own to have a normal sleep-wake cycle. Melatonin can be used as a convenient solution for falling asleep quickly but is not necessary to do so. For people with regular healthy sleeping patterns, supplementary melatonin is not needed or only recommended for short term use.
*Speaking with a doctor is recommended before beginning the use of melatonin
Disrupting Circadian Rhythm
Circadian rhythm is naturally inclined to align with the 24 hour cycle of the day, but can be shifted or disrupted by a multitude of factors. Common ways people disrupt this cycle include:
Using blue light-emitting devices at or near bedtime (Input of blue light into eyes tricks brain into thinking it's daytime)
Consuming caffeine (Depending on the dosage, caffeine can take hours for the body to process. Feelings of energy and alertness may be present well into bedtime)
Snacking before sleep (Consuming heavy or energy-filled meals before bed can lengthen time it takes to fall asleep)
Irregular sleep patterns (Going to bed or waking up at different times very often can confuse the body's internal clock of when it needs rest)
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