Within our bodies, an ancient and beautiful clock is ticking. It doesn’t measure seconds or minutes, but the sweeping cycle of day and night. This is our circadian rhythm, an internal 24 hour biological clock that governs everything from our sleep-wake cycle to our mood, metabolism, and even our immune response. When this clock is in sync with the external world, we feel energised, focused, and balanced. But in our modern, artificially lit world, it’s easier than ever to knock this delicate instrument out of tune.
Understanding how your circadian rhythm works is the first step towards reclaiming your sleep. This guide will explore the science behind your internal clock and provide evidence based strategies to reset it for a more restorative night and a brighter day.
The Master Clock: Your Suprachiasmatic Nucleus
The conductor of our body's complex biological orchestra is a tiny region in the brain's hypothalamus called the suprachiasmatic nucleus, or SCN. Comprised of about 20,000 neurons, the SCN acts as our "master clock," keeping the rest of our body in time (Mohawk, J. A., et al., 2012).
The SCN’s most important job is to synchronise our internal world with the external 24-hour cycle of light and darkness. Its primary cue for this is light. When light enters our eyes, specialised cells in the retina send a direct signal to the SCN, informing it that it’s daytime. The SCN then sends signals to the rest of the body to promote wakefulness, increase body temperature, and ramp up metabolism.
Conversely, as darkness falls, the absence of this light signal prompts the SCN to send a message to the pineal gland, another small structure in the brain, instructing it to begin producing melatonin. Melatonin is often called the "hormone of darkness" and acts as an inducer of sleep, signalling to the entire body that it's time to wind down and prepare for rest.
Coloured spots mark nuclei involved in sleep and arousal state regulation. Credit: The Picower Institute for Learning and Memory at MIT. (n.d.). Image by Lorina L. E. Lewis.
When the Clock is Out of Sync: The Effects of Circadian Misalignment
In an ideal world, our internal clock and the external environment would be perfectly aligned. We would wake with the sun and feel sleepy as darkness falls. In the modern world, however, we are constantly sending our SCN confusing signals.
Artificial Light at Night: Exposure to artificial light, particularly the blue light emitted by our smartphones, tablets, and computers, is one of the most powerful disruptors of our circadian rhythm. Studies have shown that exposure to room light before bedtime can significantly suppress melatonin production, delaying sleep onset and shortening its duration (Gooley, J. J., et al., 2011). Our master clock is essentially being told that it's still daytime, long after the sun has set.
Irregular Schedules: Our bodies thrive on routine. Inconsistent sleep and wake times, common in shift work or due to social jetlag (staying up much later on weekends), can cause a state of chronic circadian misalignment. This is akin to putting your body through a mild form of jet lag every single week, leading to daytime fatigue, poor cognitive performance, and long-term health risks (Walker, M., 2017).
Diet and Meal Timing: Emerging research also suggests that when we eat can influence our circadian rhythms. Eating large meals late at night can send conflicting signals to our peripheral clocks (the clocks in our organs, like the liver and gut), potentially disrupting the body's overall synchrony.
How to Reset Your Body Clock: 5 Science-Backed Strategies
The good news is that our circadian rhythm is not fixed; it is a flexible system that can be retrained. By sending your master clock clear, consistent, and powerful signals, you can reset your body clock and restore its natural rhythm.
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Prioritise Morning Light Exposure: The most powerful signal for resetting your clock is bright light exposure within the first hour of waking. This sends a clear "start the day" signal to your SCN, which helps to anchor your entire 24-hour cycle. Aim for at least 10-15 minutes of direct, unfiltered sunlight each morning.
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Maintain a Consistent Sleep Schedule: As much as possible, try to go to bed and wake up at the same time every day, even on weekends. This consistency is the single most effective long-term strategy for maintaining a stable and robust circadian rhythm.
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Create a "Digital Sunset": In the 60-90 minutes before bed, create an environment that signals to your brain that the day is ending. Dim the lights, and crucially, avoid the blue light from screens. This will allow your pineal gland to begin its natural production of melatonin without interruption.
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Be Mindful of Evening Meals: Try to eat your last meal of the day at least two to three hours before you go to bed. This gives your digestive system time to work and avoids sending energising signals to your body when it should be winding down.
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Strategic Use of Supplements: While not a replacement for good habits, certain supplements can help to support your body's natural sleep processes. Ingredients that provide a natural source of melatonin or the cofactors needed for its production can be a powerful tool for reinforcing your body's natural sleep-wake cycle.
At Renightalize, we are deeply committed to a scientific understanding of sleep. Our philosophy is to create products that work in synergy with your body's natural rhythms, not against them. By understanding and respecting the power of your internal clock, you can take the first step towards achieving the deep, restorative sleep you deserve.
References
Gooley, J. J., Chamberlain, K., Smith, K. A., Khalsa, S. B. S., Rajaratnam, S. M. W., Van Reen, E., ... & Lockley, S. W. (2011). Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. The Journal of Clinical Endocrinology & Metabolism, 96(3), E463-E472. Link to study
Mohawk, J. A., Green, C. B., & Takahashi, J. S. (2012). Central and peripheral circadian clocks in mammals. Annual Review of Neuroscience, 35, 445-462. Link to study
Walker, M. (2017). Why We Sleep: The New Science of Sleep and Dreams. Penguin UK.
The Picower Institute for Learning and Memory. (n.d.). The structure of sleep. MIT. Retrieved September 28, 2025, from https://picower.mit.edu/news/sleeping-brain.