INTRODUCTION
Melatonin, an indoleamine, is a natural compound produced by various organisms, including bacteria and eukaryotes. Its discovery in 1958 by Aaron B. Lerner and colleagues stemmed from the isolation of a substance from the pineal gland of cows that could induce skin lightening in common frogs. This compound was later identified as a hormone secreted in the brain during the night, playing a crucial role in regulating the sleep-wake cycle, also known as the circadian rhythm, in vertebrates.
In vertebrates, melatonin's functions extend to synchronizing sleep-wake cycles, encompassing sleep-wake timing and blood pressure regulation, as well as controlling seasonal rhythmicity (circannual cycle), which includes reproduction, fattening, molting, and hibernation. Its effects are mediated through the activation of melatonin receptors and its role as an antioxidant. In plants and bacteria, melatonin primarily serves as a defense mechanism against oxidative stress, indicating its evolutionary significance. The mitochondria, key organelles within cells, are the main producers of antioxidant melatonin, underscoring the molecule's "ancient origins" and its fundamental role in protecting the earliest cells from reactive oxygen species.
What is melatonin?
Melatonin is a hormone that’s an important part of your ability to sleep. The pineal gland produces it. Natural melatonin your body makes is also known as endogenous melatonin. It helps regulate your body’s natural sleep-wake cycle, which makes you feel tired at the end of the day and wake up after resting.
Melatonin can also be made synthetically in a lab and sold as a dietary supplement. It’s called exogenous melatonin.
What does melatonin do?
Melatonin helps control your circadian rhythm. This is your sleep-wake cycle that happens automatically about every 24 hours.
Melatonin helps your body get ready to fall asleep. It’s not a magic potion that makes you sleepy, but it’s an important chemical change in your body that happens each day.
Your pineal gland releases the most melatonin when there’s darkness and decreases melatonin production when you’re exposed to light. In other words, you have high melatonin levels at night when you’re sleeping and less in your blood during the daylight hours.
The longer the night, the longer your pineal gland secretes melatonin. That’s why some people feel sleepy earlier or more often in winter months. In winter, there’s less sunlight in the day and it stays dark longer, so your body naturally releases more melatonin in response.
How does melatonin work?
Melatonin is a chemical messenger that tells your body it’s time to relax and get ready to rest. Your pineal gland automatically releases extra melatonin around the same time every day. This usually happens when the sun goes down.
Melatonin affects cells in your brain’s hypothalamus. It tells your hypothalamus it’s time to slow activity down for the day. Once it gets the message, your hypothalamus dials back the functions it controls — like your body temperature, blood pressure and mood — to get you ready for sleep.
In your eyes, melatonin changes your retinas to get ready for rest and being less active. Melatonin helps your retinas become less responsive to light, which helps you wind down and feel less alert. When there’s more natural light the next morning, your retinas automatically become more active and your body stops releasing as much melatonin.
What are the benefits of melatonin?
Melatonin plays an important role in making sure you get enough sleep. Your body needs that natural, chemical reminder to feel tired each night. Getting enough sleep is important for every part of your health and body, including your:
-
Hair
-
Internal organs
-
Mental and emotional health
-
Skin
Melatonin’s biggest job is regulating your sleep-wake cycle. But it works in other areas of your body, too:
-
Melatonin helps maintain regular menstrual cycles.
-
Melatonin can also protect your brain health and prevent brain cells from breaking down. This breakdown can lead to dementia (including Alzheimer’s disease) and conditions like Parkinson’s disease.
-
One study found that surgically removing the pineal gland caused people to age faster than usual. Because of this, some scientists think natural melatonin may have anti-aging properties.
What are normal melatonin levels?
Your natural melatonin level can vary depending on your age and sex recorded at birth. Females typically have higher melatonin levels than males.
The level of melatonin your body produces changes throughout your life.
Newborn babies don’t produce their own melatonin. Before birth, they receive melatonin from the placenta. After birth, they can receive it through breast milk or formula. Babies develop a melatonin cycle when they’re 3 to 4 months old.
Melatonin levels are highest in kids and teens right before starting puberty. After puberty, there’s a steady decrease in melatonin levels until it evens out in your late teens. The level is stable until around age 40, followed by a natural decline for the rest of your life.
You may never know your melatonin level if you don’t experience any symptoms or need tests to measure it. If you do need a melatonin test, your healthcare provider will let you know if your levels are within normal ranges.
What are melatonin supplements used for?
Melatonin supplements are most commonly used to treat:
-
Insomnia (short-term use for trouble sleeping)
-
Jet lag due to travel across multiple time zones
-
Non 24-Hour Sleep Wake Disorder, or non-24, sleep cycles in the blind
-
Shift-work sleep disorders in people with alternating work schedules
-
Delayed sleep-wake phase disorder, due to delayed melatonin secretion
-
REM sleep behavior disorder
Melatonin dietary supplements may be promoted for many other uses, but adequate studies for effectiveness are often lacking. It has been widely studied for treatment of jet lag and other sleep disorders.
What should I avoid when taking melatonin?
-
Avoid driving, operating machinery or performing any hazardous activity for at least 4 to 8 hours after taking melatonin, or until the drowsy effects are no longer present.
-
Avoid using this medication with other prescription medications, over-the-counter drugs or dietary supplements without first checking with your doctor, pharmacist or other healthcare provider.
-
Avoid alcohol while taking this medication. It can have variable drug interactions effects. It may add to drowsiness and may cause dizziness or lead to a fall. It may also lower the levels of melatonin in your body due to an enzyme effect and reduce its ability to cause sleep.
-
Avoid coffee, tea, cola, energy drinks, or other products that contain caffeine, as it may increase the effects of the melatonin and unexpectedly increase drowsiness due to an enzyme interaction. However, clinically the effect of this interaction is unclear.
Dosage
Melatonin can be taken in doses of 0.5–10 mg per day.
However, because not all melatonin supplements are the same, it’s best to stick to the recommended dosage on the label to avoid adverse side effects.
You may also want to start with a lower dose and increase as needed to find what works for you.
If you’re using melatonin to improve sleep quality, try taking it 30 minutes before bedtime for maximum effectiveness.
If you’re using it to correct your circadian rhythm and establish a more regular sleep schedule, you should take it about 2–3 hours before you go to bed.
Safety and side effects
Research shows that melatonin is generally considered safe and non-addictive for both short- and long-term use in adults.
As of now, long-term studies on the effects of melatonin are limited to adults, so it’s not currently recommended for children or adolescents.
Some of the most commonly reported side effects associated with melatonin include nausea, headaches, dizziness, and sleepiness.
Melatonin may also interact with certain medications, including antidepressants, blood thinners, and blood pressure medications.
If you’re taking any of these medications, talk to your doctor before taking melatonin to prevent adverse effects.
How to supplement with melatonin
To aid sleep, the standard dosage ranges from 1–10 mg per day. However, the optimal dose has not been formally established.
Since not all melatonin supplements are the same, make sure to follow the instructions on the label.
Also, keep in mind that the quality of over-the-counter supplements is not monitored by health authorities. Try to choose brands that are reputable and certified by a third party, such as Informed Choice or NSF International.
Many experts do not recommend use of melatonin supplements in children and adolescents until more evidence confirms their safety in these groups.
CONCLUSION AND FUTURE DIRECTIONS
Regular physiological rhythms are important to ensure a stable internal environment by creating continuity from repetition of identical discontinuities. Several studies, based on animal models and human perinatal development, suggest that stable patterns of repeated stimuli in the form of maternal physiological rhythms, involving cross-modal perception such as regular cardiac rhythm, which provides the fetus with auditory and vibratory stimuli, allow the fetus to integrate sensory information facilitating prenatal perceptual learning and to develop a coherent representation of his or her internal and external environment.