Melatonin: What Really Puts Us to Sleep

Playing an important role in the human sleep cycle, melatonin is a substance produced by the body which sends wake and sleep signals to the brain.

The N-acetyl-5-methoxy tryptamine, or melatonin (MLT), is a hormone produced by the human pineal gland that affects the sleep and wake pattern of the human body. Scientists called it the “hormone of darkness,” since it responds to the lack of light. When the eye’s retina recognizes brightness – the rays from the sun or the glare from the gadgets – the brain inhibits the production of melatonin to keep the body awake and vigilant. However, at the absence of light, the brain’s hypothalamus triggers the pinecone-shaped pineal gland to release melatonin, signalling the body to sleep.

Derived from the substance serotonin, melatonin is processed through a series of enzymatic reactions before it is released into the blood stream and penetrate blood tissues. The signals are then received in the SCN and the pituitary gland, as well as other parts of the body, including the intestinal tract and the women's ovaries. A higher concentration exists in the SCN as this is where melatonin majorly affects the body's circadian rhythm. The hormone's binding effect in the female ovaries influences the duration and frequency of menstrual cycles.

Melatonin production peaks at night, inducing physiological changes that lulls the body to sleep; such as the lowering of the body temperature and the calming of the heart rate. Experts called it the body's chronological pacemaker. But other than its clock and calendar functions, melatonin also performs diverse properties that helps treat the body's circadian disorders, such as jet lag, sleep deprivation, and even depression.

Melatonin in Plants

But that's not all; melatonin is also present in plants. In the 1970s, researchers found melatonin in coffee extracts. Further down the road, scientists discovered melatonin's presence in vascular plants, recognizing it in various parts such as roots, shoots, leaves, seeds and fruits. This data was discovered thanks to liquid chromatography and fluorescence detection. While the levels of melatonin vary significantly in plant organs, it was shown that seeds and leaves have the highest level of this compound, and fruits, the lowest.

It was also revealed that melatonin also functions as plants’ defence against oxidative stress. In 2006's Plant Signal Behavior, researchers suggested that melatonin's scavenging capacity against free radicals make it a potent phytochemical. And just like its influence in the human circadian clock, melatonin also times the plant development in circadian rhythms, vegetation, and cell protection.

Melatonin in Animals

Startlingly, melatonin was first found in animals. Aaron B. Lerner of the Yale University School of Medicine isolated the hormone back in 1958, giving it the name due to its ability to lighten the skin colour of frogs. Earlier than that, Carey Pratt et al discovered that the pineal gland extract of cows can lighten tadpole skin.

Other than a bovine neurohormone, scientists discovered that melatonin powers the rest of the animal kingdom’s circadian clock by releasing daily and seasonal patterns of secretion. This rhythm controls the behaviours of the animals, covering their physiological, endocrine, metabolic and biochemical responses. For example, diurnal species – those who are active in the dark part of the day – are affected by the melatonin release in their body. MLT also affects reproduction, hibernation, migration and even fur changes.  

Time and Melatonin: a Conclusion

Time is crucial in all of creation. As the earth rotates in its axis, the body learns to listen, heal and recuperate, thanks to this all-essential hormone. However, other than sleep, melatonin offers a few more benefits, including:

  • Improves sleep cycles of those suffering from delayed sleep phase disorder
  • Eases jet lag symptoms
  • Offers daytime sleep quality and duration to those with shift work disorder
  • Aids insomnia sufferers, from children to adults
  • Heals mild cognitive impairment in those suffering with Alzheimer's disease
  • Prevent cell damage in patients with ALS
  • Reduces blood pressure at night

 

Let the hormone of darkness lull you to sleep. It’s your body’s own way of mending itself back so you can perform your best, every single time. Can’t sleep? Stimulate melatonin production by wearing a sleep mask to cancel the light, wherever you are.

Caris Cruz

Writer at RADICE

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