Getting an adequate amount of quality sleep is among the pillars of metabolic health. Most of us have similar sleep-wake cycles, regulated by a part of our brain called the suprachiasmatic nucleus (SCN for short). Located in the hypothalamus, SCN is considered the body’s timekeeper from its position just above the crossing for optic nerves. At night, a lack of light produces melatonin, a hormone that causes us to feel sleepy. Melatonin also impacts daily bodily activities related to a smooth metabolism that can balance between energy needs and body weight regulation.
Through the reception of light in the environment, our body can keep time. When the body receives less light, typically at night, it is detected by the receptors in our SCN (suprachiasmatic nucleus), a part of the brain that regulates physical and digestive functions based on light input.. (1) Melatonin synchronises our body’s clock, also called circadian rhythm, with that of the external environment. (9) An increase in the levels or concentration of melatonin is responsible for us to feel and be sleepy, while its ebbing is essential to keep us awake and functional.(2)
Melatonin – what it does & how?
Melatonin is a natural hormone generated by the pineal gland in the brain and then secreted into the bloodstream and cerebrospinal fluid (the fluid around the brain & spinal cord). It then transmits signals to distant organs. Darkness triggers the pineal gland to start producing melatonin while light puts a stop to the production. It is primarily recognised for its ability to aid sleep. (4) Melatonin is present in small quantities across various organs – bone marrow, eyes, and the gut. (5) Serotonin is the precursor to melatonin. It is also a neurotransmitter that is derived from the amino acid tryptophan. Within the pineal gland, serotonin is acetylated (acetylation neutralizes the positive charge of lysine, an amino acid and thus affects diverse aspects of protein function, such as stability) and then methylated (methylation is a form of alkylation) to yield melatonin. The pineal gland receives adrenergic innervation, which prompts a cascade of circadian events that ushers in the nightly generation of melatonin from serotonin. Serotonin is present at high levels in the pineal gland during the day and increases further at night in the absence of melatonin formation. Tissues expressing proteins called receptors exclusively tethered to melatonin spot the peak in circulating melatonin at night and this signals the body that it is night-time. Night-time levels of melatonin are almost 10-fold higher than daytime concentrations. The amount of light detected by our SCN from one’s retina dictates the concentration and release of melatonin to our body, which cues our body into the restful state preceding sleep. (6)(7)
Melatonin is considered the central regulatory hormone that interprets the external environment for the body’s circadian rhythm. This arrangement sets the stage for the processes in the body that regulate the harmony between energy needs and body weight. The circadian modulation of carbohydrates metabolism is vital for glucose homeostasis and energy balance. Imbalances in glucose and insulin tissue and blood levels have been associated with metabolic disorders such as obesity, metabolic syndrome, cardiovascular diseases and type 2 diabetes. Melatonin, the pineal hormone, is the dominant mediator molecule for the cohesion between the cyclic environment and the circadian distribution of physiological and behavioral processes as well as the optimization of energy balance and body weight regulation.
Melatonin regulates insulin through signaling brown adipose tissue – a type of fat. Further, melatonin levels bifurcate our physiological processes into two. When melatonin is low, it cues the body for activity, wakefulness, & feeding. When melatonin is high, it cues the body for rest, sleep, and fasting. (2) Shifts in melatonin patterns – whether from illuminated environments or patchy sleep – consequently disrupt circadian rhythms and metabolic processes.
Melatonin and metabolic health
A fluctuation in melatonin levels can disrupt metabolic processes, leading to consequences for groups like evening and night shift workers, people who eat at later hours of the night, as well as roughly 3 million adult Americans who use melatonin over the shelf. (3) This explains the discomfort and digestive problems arising from jet lag. This is also affiliated to the ways in which meal timings can affect sleep and weight change.
The molecular clock that modulates the timing of every physiological process like the secretion of hormones and neurotransmitters, the immune cell activity and the time you feel sleepy, alert or depressed, keeps ticking within every cell of the body. These timekeepers work in harmony with each other and with the time of the day. This synchronicity is achieved through the suprachiasmatic nucleus (SCN), the small speckle of brain tissue described above. It functions in tandem with photoreceptive retinal ganglion cells (ipRGs), light-receptive cells behind the eye. The purpose of these clocks is to foresee and prepare for consistent events in the environment. Varied biochemical reactions are at work at different times of day, facilitating our internal organs to switch gears and recover.
“Unless we have access to light, we struggle to stay awake and eat at the wrong time. The timings of our meals can also turn the hands of the clocks in the liver and digestive organs, even though the timepieces in our brain cells are unchanged.” says Satchin Panda, a circadian biologist to a leading science publication.
Melatonin and glucose metabolism
In our bodies, glucose is metabolised as insulin lowers blood glucose by increasing its uptake in the liver and muscles through the processes of glycolysis and glycogenesis. There is research (2) stating that melatonin replacement therapy, carried out suitably in terms of dose quantity & strength, as well as at the right time of the day, could be a contributing factor in the stabilising of blood glucose levels in people with diabetes. The evidence of melatonin triggering insulin and enhancing white blood cell function signify it as a treatment option to reestablish glucose homeostasis – the condition in which insulin and glucagon aid the maintenance of a suitable blood glucose level.
Other research indicates that high melatonin levels, typically taking place at night, overlapping with food consumption may have a negative impact on glucose sensitivity – the body would process glucose less effectively as melatonin brings the circadian rhythms to a restful, fasting state to encourage sleep. This is in contrast to the state of awakened, energy-led active state that metabolism is best carried out in.(3)
Melatonin and metabolic syndrome
Metabolic syndrome is the label given to a range of simultaneously occurring conditions that raise one’s risk of heart disease, stroke, and type 2 diabetes. It includes conditions like high blood sugar and pressure, pockets of fat around the waist, and fluctuating cholesterol and triglyceride levels. Melatonin can be an important factor when it comes to the prevention and the treatment of metabolic syndrome. Its levels are found to be lower in conditions linked to insulin resistance (a diabetic precondition), such as metabolic syndrome. A rise in melatonin levels – whether through natural or organic in-body means, or through external consumption, holds the potential to be a treatment for metabolic syndrome.
Melatonin and inflammation
Inflammation is a natural occurrence in our body when it detects alien substances or threats. It is a protective process that has the potential to cause us damage when it perceives a threat that isn’t real – whether at infection or wound level. Melatonin carries certain anti-inflammatory properties. (11) It has a range of ways to minimise tissue damage during an inflammatory reaction. It absorbs toxic free radicals to reduce macromolecular impact across various organs. (13) These toxic free radicals aid the body’s inflammatory response and the consequent tissue damage. It also indirectly inhibits the production of molecules with adhesive properties that aid leukocytes to stick to endothelial cells. As such, it takes the edge off certain cell movement and swelling that contribute to tissue damage. Finally, consumed melatonin can drop the count on inflammation markers and holds the potential to prevent and treat inflammation disorders – such as chronic inflammation. (14)
Melatonin and weight loss
Melatonin levels dictate the body’s digestive and regulative processes. Certain studies indicate that melatonin could catalyse metabolism and enhance our capability to reduce weight. This takes place in two ways (16)
- It uses fat as energy (glucose) instead of as a stored form of energy
- It allows the cell’s powerhouse, mitochondria, to process fat at an improved capacity
These qualities make a case for melatonin to be a complementary weight loss tool along with an increase in physical activity or switching to a holistic diet. (15)
Melatonin and stress
An increase in melatonin levels puts the body in a state of rest and relaxation. It is a natural antidote to stress and its impact on cortisol and the development of related states like anxiety. In group tests on rats, subjects following CIS protocal were administered with 10mg per kg a day of melatonin. (17) At the end of a 6-week period, such rats had a visibly reduced amount of anxiety-driven behaviour. (Do note that Ultrahuman does not recommend or prescribe the use of any melatonin supplements). They also had greater levels of serotonin – the daylight hormone that signals an active state to the circadian rhythm, noradrenaline (22) – a neurotransmitter that controls brain attention and responsiveness, and oxytocin – a hormone that is responsible for social bonding (23).
In another study, it was found that at night, when the endogenous level of melatonin is high in rats, exposure to stressful stimuli leads to a lower incidence of gastric ulceration than during the day. It was also found that small doses of melatonin inhibited gastric stress ulceration in a dose dependent manner, indicating the involvement of melatonin in stress.
Cortisol, a hormone produced by stress, impacts melatonin synthesis in the pineal gland negatively at night. It may do so with a spike on serotonin, causing a disturbance in the functions melatonin carries for metabolism, relaxation, and regulating the body’s active state. (18) In a study on Korean high school students, there is also a pointed reverse relationship between cortisol and melatonin. (24)
How to Boost Your Melatonin Levels Naturally
Melatonin has found popularity and common use as an over-the-counter supplement. It is primarily taken as an aid in sleep. However, research is essential to prove the efficacy of its over-the-counter use. It is possible to enhance one’s melatonin levels without consuming it at all. (10) Some methods to do so are:
- Be mindful of light: using phones or screens inhibits melatonin, as does a fully lit room at night. Sunlight produces serotonin, which essentially reduces melatonin levels.
- Some fruits and vegetables have a melatonin presence to them. This list includes asparagus, olives, corn, cucumbers, and pomagranate.
- Physiological relaxation: a warm bath to lower cortisol, ie, the stress hormone, or attempting conscious breathing are prudent ways to enhance melatonin production.
Conclusion
Known for its ability to help us rest and subsequently sleep, melatonin is produced in the pineal gland at the end of the day in environments of suitably low light. It is a key hormone produced near the brain that regulates and activates our circadian rhythm, or the body’s internal clock, aligning it with the external world. Melatonin has properties that nudge digestion and metabolism as well as general health in various ways. It can contribute to fat loss, prevent tissue damage during periods of inflammation. The right levels of melatonin are important for the body to carry out its functions. During the day, the body requires low levels that signal it to act, eat, and digest. At night, the body requires higher levels to enter a state of rest, fasting, and sleep.
Disclaimer: The contents of this article are for general information and educational purposes only. It neither provides any medical advice nor intends to substitute professional medical opinion on the treatment, diagnosis, prevention or alleviation of any disease, disorder or disability. Always consult with your doctor or qualified healthcare professional about your health condition and/or concerns and before undertaking a new health care regimen including making any dietary or lifestyle changes.
References
- Your Body’s Internal Clock and How It Affects Your Overall Health – The Atlantic
- Melatonin: A Silent Regulator of the Glucose Homeostasis | IntechOpen
- MELATONIN EFFECTS ON GLUCOSE METABOLISM: TIME TO UNLOCK THE CONTROVERSY (nih.gov)
- Melatonin for Sleep: Uses, Dosage, Side Effects & More (healthline.com)
- Melatonin: Pharmacology, Functions and Therapeutic Benefits (nih.gov)
