Sleep disruption, low energy, and hormonal changes are some of the most common concerns I see in clinic. And more often than not, they trace back to one underlying system that doesn’t get enough attention – your circadian rhythm.

Melatonin is often described as the “sleep hormone”, but in practice, it is better understood as a timing signal within a broader biological rhythm system that regulates sleep, hormones, metabolism and energy.

Recent research published in PubMed continues to highlight how circadian rhythm disruption is linked not only to sleep disturbances, but also to metabolic changes, mood shifts, and hormonal imbalance. When out of sync, everything feels harder – sleep becomes lighter or fragmented, energy dips during the day, and hormonal symptoms can intensify.

In this melatonin and circadian rhythm guide, I’ll walk you through how melatonin and circadian rhythm really work, and how you can support them naturally.

For a more in-depth information on circadian rhythm and its functions, read my Circadian Rhythm Health article.

If you’re also experiencing gut symptoms alongside sleep disruption, you may find it helpful to read my guide on gut health and the microbiome connection to overall wellbeing helpful. These systems are deeply interconnected.

Quick Answers

What is melatonin?

Melatonin is a hormone produced by the brain that regulates sleep-wake cycles in response to light and darkness. Melatonin is also an important antioxidant.

What controls circadian rhythm?

Your circadian rhythm is primarily regulated by light exposure, especially morning sunlight, along with cortisol rhythm, lifestyle habits, and metabolic signals.

Why does this matter after 40?

Hormonal changes can disrupt sleep, stress resilience and energy production, making circadian rhythm regulation much more important in midlife. Circadian rhythm shifts during perimenopause and menopause making circadian stability more important than ever.

Key Definitions

Circadian rhythm: Your internal 24-hour body clock that regulates sleep-wake cycles, hormone secretion, digestion, metabolism and energy.

Melatonin: A hormone and antioxidant produced mostly during the day and released at night in alignment with the body’s internal clock. It helps to initiate and support sleep.

Cortisol rhythm: The daily pattern of cortisol release which should peak in the morning and gradually decline toward the night.

What is Melatonin and Why Does it Matter?

Melatonin is a naturally occurring hormone primarily produced by the pineal gland in response to darkness. It plays a central role in regulating sleep timing, circadian rhythm, cellular repair, immune signalling, and overnight recovery processes.

While melatonin is commonly referred to as the “sleep hormone”, its function is much broader than sleep alone. Melatonin acts as a downstream signal within the body’s wider circadian rhythm system, helping coordinate biological processes according to the light-dark cycle. It’s also a powerful antioxidant.

This means melatonin does not work independently. Its production and release are strongly influenced by:

  • Morning sunlight exposure
  • Evening light exposure
  • Sleep timing
  • Stress and cortisol patterns
  • Meal timing and metabolic signals
  • Circadian rhythm alignment

When circadian rhythm becomes disrupted, melatonin production often becomes delayed, reduced, or inconsistent.

While commonly associated with sleep, most melatonin is produced during the day and released at night in alignment with the body’s internal clock. Only 5% of melatonin is produced at night by the pineal gland, approximately 95% comes from multiple tissues throughout the body and is synthesised in the mitochondria of these cells. 

If you would like a broader understanding of how the body clock regulates sleep, hormones, metabolism, and nervous system function, read my foundational guide on: Circadian Rhythm Health

Melatonin and Circadian Rhythm: Understanding the Connection

Melatonin is best understood as part of the body’s internal timing system rather than simply a sleep chemical. I often explain this to clients as a light-driven timing system rather than a single hormone issue or a hormone deficiency problem.

The circadian rhythm system acts as the body’s master biological clock, coordinating:

  • Sleep-wake cycles
  • Cortisol rhythm
  • Hormone timing
  • Metabolic activity
  • Digestive function
  • Cellular repair

Melatonin is one of the key signals produced by this system in response to darkness. Melatonin doesn’t force you to sleep. It signals that it’s time to wind down. That signal is heavily influenced by your exposure to light and darkness.

  • Morning light helps “set” your circadian rhythm for the day
  • Darkness in the evening allows melatonin to rise
  • Artificial light, stress and irregular routines can disrupt this cycle

When the timing is off, melatonin may be released too late, too early, or not in a strong enough pattern to support deep, restorative sleep.

In a healthy circadian pattern:

  • Cortisol rises in the morning to promote alertness and energy
  • Melatonin rises in the evening to support rest, repair, and sleep initiation

When this timing system becomes misaligned, the body may experience:

  • Difficulty falling asleep
  • Night waking
  • Light or fragmented sleep
  • Daytime fatigue
  • Evening alertness or “wired but tired” patterns

For many people, especially after 40, the underlying issue is not simply “low melatonin”, but broader circadian dysregulation driven by modern lifestyle patterns such as artificial light exposure, stress, irregular schedules, and insufficient natural daylight.

That is why restoring circadian rhythm often improves melatonin function naturally.

Key insight:
Morning light exposure anchors your internal clock, while evening darkness allows melatonin to rise at the correct time. However, modern lifestyle factors such as artificial lighting, irregular sleep patterns, and stress can shift this timing system out of alignment.

Learn more about hidden impacts of artificial lights on your health, melatonin function and biological clock in my article.

If you want a deeper, practical step-by-step approach to restful sleep, I expand this further in my Sleep Better Tonight guide, where I walk through real-world circadian reset strategies.

How Sunlight Regulates Melatonin

One of the simplest and most powerful circadian regulators is morning natural light exposure. Sunlight regulates melatonin production by influencing the body’s circadian rhythm. Exposure to light, especially in the morning, suppresses melatonin levels, signalling the body to be alert and active, while darkness increases melatonin production, preparing the body for sleep.

This is now strongly supported in circadian biology research and is a key factor discussed in sleep and metabolic studies indexed in PubMed. Your body relies on natural light to anchor your circadian rhythm. Without it, the entire system can drift.

In clinical practice, this can look like:

  • Difficulty falling asleep
  • Waking during the night
  • Feeling tired but wired
  • Low morning energy

Even 10–20 minutes of morning light daily can make a measurable difference. It can help:

  • Anchor melatonin timing
  • Improve sleep onset in the evening
  • Support cortisol rhythm stability
  • Enhance daytime energy regulation

This is especially relevant if you are working on hormonal balance or perimenopause-related sleep changes.

This is also something I cover in my broader sleep optimisation and circadian rhythm articles, where I go deeper into light exposure, cortisol timing and evening routines (link to sleep blog hub).

Clinical insight
Natural light is particularly important if you are working on improving sleep as part of a broader hormonal reset or menopause transition. Light exposure is one of the most powerful “non-supplement” tools we have.

Melatonin and Hormonal Health

This is where I see the strongest clinical overlap. During perimenopause and menopause, changes in oestrogen and progesterone can influence:

  • Sleep depth
  • Night waking frequency
  • Stress sensitivity
  • Thermoregulation

At the same time, melatonin production may become less stable with age. There’s usually a deeper pattern underneath. Sleep changes in midlife are rarely just “sleep problems”, they are often part of a broader hormonal transition. What I often see is:

  • Increased night waking
  • Early morning waking
  • Reduced sleep depth
  • Heightened stress sensitivity

Circadian rhythm disruption doesn’t just affect sleep, it can amplify hormonal symptoms. Supporting this system becomes one of the most effective ways to stabilise energy, mood and overall resilience.

If you’re navigating hormonal shifts, I go deeper into this in my menopause support and hormonal balance framework. Sleep disruption here is rarely isolated, it is usually part of a broader hormonal and stress adaptation pattern.

Understand what your menopause symptoms and signs are really telling you in my comprehensive guide.

Circadian Rhythm and Metabolism

Circadian rhythm is not just about sleep – it is also a metabolic timing system. This surprises many people: your circadian rhythm also regulates:

  • Blood sugar balance (glucose metabolism)
  • Insulin sensitivity
  • Appetite regulating hormones
  • Mitochondrial energy production

Disruption in this system is increasingly associated with metabolic changes, weight resistance, and fatigue patterns in midlife populations.

This is also closely linked to gut health, which I cover in my microbiome and gut–brain axis guide.

Melatonin, Sleep and Ageing

Melatonin is being researched for its potential anti-ageing properties. It acts as an antioxidant and has been shown to support cellular functions that decline with age, including brain health support.

As we age, melatonin rhythms can become disrupted due to:

  • Reduced daylight exposure
  • Increased artificial light at night
  • Hormonal changes
  • Chronic stress and inflammation

This can contribute to:

  • Insomnia
  • Early waking
  • Non-restorative sleep

The Gut–Sleep Connection

One of the most overlooked aspects of sleep regulation is the gut–brain axis.

The gut microbiome influences neurotransmitter activity and inflammatory signalling, both of which can indirectly affect sleep quality and circadian rhythm stability. When gut health is compromised, sleep quality often follows.

This is why I rarely treat sleep in isolation in clinical practice – it is part of a wider interconnected system involving digestion, hormones, and metabolic health.

Why Melatonin Matters After 40

Melatonin production declines with age, particularly in women over 40. At midlife, and particularly during perimenopause and menopause, women experience shifts in:

  • Estrogen
  • Progesterone
  • Cortisol

These can directly affect melatonin production and signalling, increasing vulnerability to sleep, mood, and metabolic challenges. This m)elatonin and circadian rhythm guide highlights changes that happen in midlife transition. Find out more about the sleep-hormone connection in my article.

Common Causes of Melatonin Disruption

Melatonin disruption can significantly affect sleep patterns, nervous system and overall health. The key causes are:

  • Inadequate morning sunlight and also during the day
  • Excessive evening light exposure
  • Artificial light exposure to blue light (screens, phones, TVs)
  • Shifted sleep–wake timing
  • Irregular sleep schedules
  • Shift work
  • Travel
  • Chronic stress and inflammation
  • Ageing
  • Medical conditions such as anxiety and depression

Understanding and managing these multifactorial causes can help maintain and improve melatonin levels.

How to Support Melatonin and Circadian Rhythm Naturally

The good news is that this system responds very well to consistent, simple inputs. From a clinical perspective, the most effective natural ways to support melatonin and circadian rhythm are often simple but consistent.

Here are the foundations I focus on in practice:

  • Get natural light exposure within the first hour of waking
  • Reduce artificial light in the evening, especially screens and bright lights
  • Have dark nights – dark, quiet bedroom with light blocking curtains, if needed
  • Keep consistent sleep and wake times
  • Support blood sugar balance throughout the day
  • Manage stress nd cortisol load
  • Support gut health as part of your overall strategy
  • Review nutrition patters – e.g. investigate nutrient deficiencies that can interfere with sleep such as tryptophan (an amino acid found in foods like turkey, fish, eggs, and dairy), as well as magnesium and vitamin B6.

These circadian rhythm and sleep regulation strategies may sound simple, but when applied consistently, they can shift circadian rhythms and sleep patterns quite significantly.

If you would like personalised support with this, I offer online naturopathic consultations Australia-wide where we assess sleep, gut health, and hormones as an integrated system.

Common Questions

Why is melatonin not working for me?

Melatonin supplements can be useful short-term in select cases but they correct circadian misalignment if underlying light exposure, stress, or metabolic timing is disrupted.

Does sunlight really affect sleep hormones?

Yes. Morning light is one of the most powerful regulators of circadian rhythm and melatonin timing.

How long does it take to reset circadian rhythm?

With consistent changes, many people notice improvements within 1–2 weeks, although deeper regulation can take longer.

Can menopause disrupt circadian rhythm?

Yes. Hormonal shifts can alter sleep patterns, cortisol rhythm and melatonin production.

Key Takeaways

  • Melatonin is primarily a daytime-produced hormone
  • Sunlight is essential for healthy melatonin rhythm
  • Midlife hormonal shifts can disrupt melatonin e.g. sleep problems in menopause
  • Circadian and lifestyle support matters more than supplements

Final Thoughts

When sleep becomes disrupted, it is rarely just about melatonin alone. It is about timing, light exposure, metabolic stability, hormonal transitions, and gut–brain communication working together as one system.

Once you start addressing circadian rhythm as a whole-body regulatory system, rather than an isolated sleep issue, outcomes tend to be more stable and sustainable.

By supporting your circadian rhythm through light, lifestyle and metabolic balance, you’re working with your biology rather than against it. And that’s where sustainable change happens. This melatonin and circadian rhythm guide is a good place to start.

If sleep has become unpredictable or you’re navigating hormonal changes, addressing circadian rhythm can make a meaningful difference. My eBook: Morning light to better nights: the practical circadian health handbook can guide you how to align circadian rhythm and sleep in practical and simple ways.

Next Steps

If you’re unsure how this information applies to your own health, individual support can make all the difference. I offer online consultations for Australia-based clients.

👉 Learn More About Consultations

Using information is different from applying it. Education is an important first step – and you’re already doing that. If you’re ready for guidance that takes your unique health history into account, I’m here to help. 

I work virtually as an online wholistic naturopath and nutritionist helping clients based anywhere in Australia. Book an online consultation or click on the button below to book a free 20-minute initial discussion to talk about your circumstances and how I can help.

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I look forward to connecting with you and to working with you towards better health and wellbeing.

Best of Health

Joanna Sochan
Wholistic Health and Lifestyle Therapist
Integrative health support combining clinical evidence and traditional naturopathic wisdom for lasting health and wellbeing

References and Sources

If you’d like to learn more about the natural melatonin cycle and circadian rhythms, I wrote a series of in-depth and practical blogs to explain why they have key importance to health and wellbeing for everyone.

Disclaimer: The above material is for informational and/or educational purposes only. It should not be used to self-diagnose and it is not a substitute for medical advice, diagnosis, treatment, prescription or recommendation. All viewers of this content, especially those taking prescription or over-the-counter medications, should not make any changes in their health regimen or diet before first consulting a doctor or other qualified health provider with any questions they may have regarding a medical condition or their particular circumstances.

Joanna Sochan is a Wholistic Naturopath and Nutritionist and founder of Naturimedica Wholistic Wellcare. She has a passion for helping her clients transform their lives by becoming healthy and well naturally. Joanna has 15+ years experience in clinical practice and has special interest in solving complex cases, gut health, food sensitivities, hormone imbalances, detox and weight loss. She helps clients individually (mostly online) Australia-wide and also offers online therapeutic programs, eCourses and self-help books. View full bio.