Throughout the ages, mothers have been singing lullabies in the dark of night to put their babies and toddlers to sleep. In a similar vein, our bodies sing a nightly lullaby to put us to sleep – with a song called melatonin. Although this song has no lyrics, it does come with a regular rhythm.
What is melatonin?
Melatonin is a neurohormone that prepares the body for sleep, and it plays a crucial part in regulating the body’s circadian rhythm, also known as the biological clock. Our bodies internally have a natural, biological timer present in each of our cells, which recognize sleepiness and wakefulness in a 24-hour sleep-wake cycle. Melatonin not only regulates the daily circadian rhythm, but also a seasonal rhythm, with higher levels of melatonin in the autumn and winter when nights are longer, and lower levels in spring and autumn when nights are shorter.
Where does melatonin come from?
The hormone melatonin is produced naturally from the amino acid tryptophan by the pineal gland at night-time. The pineal gland is a tiny endocrine gland that is situated near the center of the brain. The production of melatonin results from the detection of light and dark by the retina of the eye, meaning the production of melatonin is inhibited during the light of day and stimulated in the dark of night. Photoreceptor cells in the retina send the light or dark signals along the optic nerve to the suprachiasmatic nucleus (SCN) in the hypothalamus of the brain, from where these signals are transmitted to the pineal gland. The SCN is the brain’s master clock, which controls the production of melatonin and other hormones in the 24-hour cycle of day and night.
When activated at night, the pineal gland secretes melatonin into the bloodstream as well as into the cerebrospinal fluid around the brain and spinal cord, from where it is carried to all areas of the body. Receptors in the cells and tissue of the body detect the peak in melatonin being circulated at night (about ten times higher than daily levels) and signals to the body that it is time to sleep. Melatonin levels typically begins to rise around dusk and peak during the night at around 02:00, before falling to very low levels shortly before dawn. The duration of melatonin secretion by the pineal gland is between 7,5 and 8 hours.
Melatonin helps to promote sleep by assisting the body’s master clock in regulating sleep-wake cycles, resulting in healthful sleeping patterns. When your biological clocks function properly and you sleep well at night, it helps to improve your mood as well as energy levels and overall health.
Around sunrise the retina starts to detect large amounts of light. When these signals reach the pineal gland, the production of melatonin is suppressed and synchronized with a rise in the secretion of hormones such as cortisol and insulin in order to stimulate wakefulness in the morning as well as focus, energy and alertness during the day.
Other functions of melatonin:
As scientists continue to study how the hormone melatonin works in the body, understanding how it contributes to health and disease protection is expanding rapidly.
Melatonin is known for its powerful role as an antioxidant that may work to protect the body against cell damage, particularly oxidative damage in brain cells. As an antioxidant and scavenger of harmful oxygen radicals, melatonin is considered to play an important role in protecting against cognitive impairment and neurodegenerative diseases such as Alzheimer’s.
The antioxidant effects of melatonin help to protect the mitochondria (which generates energy currency inside the cells in the body), as melatonin – working synergistically with vitamin D to optimize mitochondrial function – has the ability to enter the mitochondria and protect it from oxidative damage.
Melatonin also appears to have protective antioxidant effects in physiological systems, such as the cardiovascular and gastrointestinal systems.
Through melatonin’s role in immune regulation, it is known that melatonin interacts with and enhances the body’s immune system, as well as having an anti-inflammatory effect by facilitating the decrease of the immune system’s inflammatory response.
Recent research has indicated that melatonin shows promising potential to assist in treating certain forms of cancer, by slowing the growth of certain types of cancerous tumours. Melatonin has also shown promising results in the treatment of the side effects of other cancer treatments, such as chemotherapy. Research in this regard is ongoing.
The seasonal rhythm of melatonin production according to the length of the solar day also plays a role in the seasonal breeding rhythm of animals, as various species time their mating or breeding to coincide with favourable seasons, such as spring.
Keeping the lullaby active
A regular good night’s sleep and getting plenty of bright sunlight during the day helps to set your circadian clock and optimize melatonin production. There are, however, many factors that can affect optimal melatonin production and sleeping patterns.
Exposure to bright lights during the evening and blue light from electronic screens and LED light bulbs before going to bed can inhibit the production of melatonin. You can increase natural melatonin levels a few hours before going to bed by dimming all lights and avoid watching TV or other electronic screens, such as cellphones and computer screens.
Research has found that many children and adults with autism spectrum disorder (ASD) may have lower levels of nighttime melatonin, and correlations between abnormal melatonin levels and the severity of ASD were also found. Supplementing with melatonin may be effective to improve sleep quality and quantity in people with ASD.
Melatonin supplements can be taken to assist with a variety of sleep disorders, such as insomnia, or to adjust sleep schedules after your biological clock has been thrown out of kilter by events such as jet lag after crossing time zones, or due to doing shift work. High levels of stress can also interfere with sleep patterns.
Older people may also experience sleep disorders, as our bodies produce less melatonin as we age. Melatonin supplements can effectively be used for treatment of age-related insomnia.
Melatonin supplements should be taken after dinner or during the course of the evening and not directly before going to bed, as they are aimed at boosting the body’s natural melatonin levels and don’t work like quick acting sleeping tablets.
Medical advice is recommended to help determine the real cause of sleep disturbances, before taking melatonin supplements.
While melatonin supplements are not sedatives or sleeping tablets, it helps to shorten the time it takes to fall asleep, as well as improving the quality of sleep and increasing overall sleep amounts.
The common dosage, to get the lullabies going again, usually ranges from 1-10 mg per evening..
Melatonin. Published online and reviewed March 2018. You and your hormones, an education resource from the Society of Endocrinology. (www.yourhormones.info)
Melatonin: Pharmacology, functions and therapeutic benefits. Published in Current Neuropharmacology, April 2017. (www.ncbi.nlm.nih.gov)
Melatonin. Published in Encyclopedia Britannica. (www.britannica.com)
Side effects of melatonin: What are the risks? Published 8 February 2018. Healthline. (www.healthline.com)
How melatonin can help you sleep and feel better. Published 3 September 2017. Healthline. (www.healthline.com)
Understanding melatonin: How melatonin can help sleep and bio time. Published 6 June 2017. Sleep Doctor. (www.thesleepdoctor.com)