Melatonin: the sleep hormone explained – Netdoctor

Last Updated on November 27, 2020 by

Often referred to as the ‘sleep’ hormone, melatonin is central to your body’s sleep-wake cycle. Levels rise gently throughout the evening and peak during hours of darkness, regulating the timing of our 24-hour internal clock, the circadian rhythm, as we drift off into hour upon hour of deep, consistent, high quality slumber.

That’s how it should go, anyway. But our modern lifestyles frequently interfere with the functioning of this physiological process – oftentimes without us even knowing it – leaving us feeling fatigued, overstimulated, and craving a solid night’s kip. The good news is, there are ways to re-calibrate your melatonin levels without popping a supplement.

We spoke to psychologist Dr Juliet Anton, GP and medical advisor at Prescription Doctor Dr Giuseppe Aragona, therapist Juan Carlos Gouveia and business psychologists Johanna Scheutzow and Elissa Makris of NHS-backed wellbeing platform Thrive to talk us through the intricacies of natural melatonin:

What is melatonin?

Melatonin plays an important role in your circadian rhythm, which is a naturally occurring 24-hour cycle that is part of the body’s internal clock. Darkness signals your brain to release melatonin, while light – be it artificial, natural, or the blue light emitted from our TV and phone screens – halts production.

‘The body will produce melatonin as the days start to turn to night, peaking during the middle of the night to the early hours of the morning and will then start to reduce during daylight hours,’ says Dr Aragona. ‘Melatonin is an essential hormone because it encourages and enables us to have a good, uninterrupted night’s sleep.’

In humans, the hormone is produced by the pineal gland in the brain. But we aren’t the only melatonin producers in nature.

In humans, the hormone is produced by the pineal gland in the brain. But we aren’t the only melatonin-producers in nature. ‘It’s naturally present in a number of organisms, such as bacteria, algae, fungi, plants, insects, vertebrates and humans,’ says Scheutzow, ‘but it can also be found in different types of foods such as vegetables, fruits, rice, and wheat.’

When the hormone is created within the body, it’s known as endogenous melatonin. When produced artificially, it’s exogenous melatonin. Sometimes this kind of melatonin is sold as a dietary supplement in pill, capsule or liquid form. However, there is very little data about the long-term effects of melatonin supplements in children or adults, and there are issues related to the dosage and quality of such sleep aids. For the purposes of this article, we’re referring to the natural occurring hormone only.

the way this ‘sleep’ hormone acts on your body is complex, and begins in the brain

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Does melatonin help you sleep?

Melatonin doesn’t put you to sleep, but it does promote it. The way the hormone acts on your body is complex, and begins in the brain. ‘The suprachiasmatic nucleus – a small bit of the brain located in the very centre of your head – is the master clock for the body and is connected to the eyes directly,’ says Makris. ‘This master clock regulates how much melatonin is released into the brain and the rest of the body.’

The hormone is produced by the pineal gland and secreted into both the bloodstream and cerebrospinal fluid – a clear colourless fluid found in the brain and spinal cord, says Scheutzow, ‘one of its functions is for protection and buoyancy of the brain’. Approximately 90 per cent of melatonin is cleared in a single pass through the liver, she adds, while any remaining unmetabolised melatonin is eliminated when you urinate.

The onset of melatonin secretion typically occurs between approximately 10pm and 11pm and peaks at around 3am to 4am during a regular sleep cycle, Makris continues. ‘The suppression of melatonin production occurs at approximately 7am to 9am,’ she says. ‘However, it’s important to keep in mind that melatonin rise can vary considerably among individuals. External factors, such as light exposure, play a significant role.’



What else does melatonin do?

Melatonin is no one-trick pony. Aside from regulating the sleep-wake cycle, the hormone has a variety of actions within the body, including ‘antioxidant actions, bone formation and reproduction’, says Scheutzow. It offers protective effects, especially for psychiatric disorders and cardiovascular disease, she says, and is associated with the body’s thermoregulatory system.

‘As the core body temperature decreases, melatonin levels in the blood increase,’ Makris explains. This is why you find it easier to drift off after a hot bath – the warm water draws blood away from your core, cooling your body internally.

Melatonin has an enhancing effect on our immune system, regulating cytokine expression and inhibiting cell death in immune cells.

‘Melatonin has also been found to have an enhancing effect on our immune system,’ Makris continues. ‘It stimulates natural killer cell activity, regulates cytokine expression and inhibits cell death in immune cells.’

And that’s not all. ‘Melatonin helps us maintain our daily mood, promotes cognitive functioning, and protects us from gastrointestinal problems, including ulcers,’ says Dr Anton. The hormone may even have protective effects against cancer, says Gouveia, by enhancing the impact of treatments and reducing stroke damage. ‘It may also reduce the damaging effects of obesity on the body by lowering inflammation – and slow mental decline in people with dementia,’ he adds. Phew.



What causes low melatonin levels?

From nutrient deficiencies to high stress levels, many everyday habits and lifestyle factors can lead to low melatonin levels. ‘Exposure to too much light at night – especially blue light from TVs, computers, tablets or mobile phones – not getting enough natural light during the day, and shift work can all affect melatonin production levels,’ says Gouveia.

Drinking alcohol before bed and smoking have been shown to inhibit melatonin. ‘Research indicates that drinking moderate amounts of alcohol in the evening suppresses melatonin by nearly 20 per cent,’ says Scheutzow. ‘Smoking causes oxidative stress – imbalance between free radicals and antioxidants in the body – and decreases blood melatonin levels.’

Medical drugs – especially non-steroidal anti-inflammatory drugs (NSAIDs) and beta blockers – can also interfere with melatonin, says Gouveia, as can certain health conditions, including dementia, mood disorders, chronic pain, cancer and type 2 diabetes. ‘Sleep disorders like insomnia, sleep related breathing disorders, and circadian rhythm disorders are also contributing factors to lower melatonin levels,’ he says.

People at risk of low melatonin levels include:

  • People with alcohol dependence: Alcohol dependent people have reduced levels of melatonin, which are also slow to rise, says Makris. ‘This negatively affects their ability to fall asleep,’ she explains.
  • Elderly people: ‘Melatonin levels tend to decline over the life-span and this is evident in elderly people who find it difficult to get a good night’s sleep,’ says Dr Anton.
  • People who suffer from chronic stress: ‘Chronic stress can negatively influence the synthesis of melatonin,’ says Dr Anton. When the stress hormone cortisol is released, it counteracts the production of melatonin, she explains.
  • Pregnant women: Pregnant women have fluctuating levels of melatonin, says Scheutzow. ‘During the first and second trimester, the high levels of melatonin during the night are lower,’ she says. ‘Melatonin rises until the child is born, where levels are shown to be the highest. After the birth, levels will go back to normal.’
  • Substance misuse: ‘Prolonged exposure to external substances has been associated with physical changes in the brain biochemistry, which could lead to melatonin deficiency and thus, a disruption in circadian rhythm,’ says Dr Anton.

    Unfortunately, low melatonin levels are known to contribute towards a number of diseases usually seen among elderly people, says Gouveia. ‘Parkinson’s, Alzheimer’s and other types of dementia increase in prevalence with age and also are tied to low melatonin levels,’ he says.



      How to increase melatonin production

      Melatonin is manufactured from tryptophan, an amino acid that is only accessible through diet. Gouveia recommends the following food sources to boost your melatonin stores:

      • Sea vegetables like kelp, seaweed and spirulina are rich sources.
      • Nuts, especially pistachios, contain the highest concentration of melatonin among plant foods.
      • Eggs and fish are also good sources of the hormone.
      • Other foods with high levels include grapes, cherries, strawberries, tomatoes, peppers and mushrooms.

        If you’re concerned about melatonin suppression, focus on reducing your exposure to blue light in the evenings, reduce your alcohol intake and refrain from smoking. But resist the temptation to take supplements. ‘Melatonin supplements should not be taken unless recommended by the doctor,’ says Scheutzow. ‘The body is able to naturally regulate melatonin levels so it can be harmful to intervene if not necessary.’



        Last updated: 27-11-20

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