Healing Space | Health effects of light exposure: Here comes the sun

Circadian rhythm: When we systematise our habits to night and day schedules, then the body finds it easier to fall asleep and wake up, it knows when to ramp up activity and when to shut it down. (Illustration by Suneesh K.)

Note to readers: Healing Space is a weekly series that helps you dive into your mental health and take charge of your wellbeing through practical DIY self-care methods.

Light is a zeitgeber, a ‘synchroniser’ for the body. We are beings with circadian rhythms that deeply affect the state of our well-being. Circadian rhythms are the physical, mental, and behavioural influences a day has on us (‘circa’ means ‘of the day’). It is decoded by a cluster of 20,000 neurons in the base of the hypothalamus known as the suprachiasmatic nucleus. It governs how we sleep, eat, our hormones, how fit we feel and how well adjusted we are to our environments. When we rise and sleep and eat along with the light of the sun, signals are sent down to the nucleus that activate the release of hormones such as cortisol in time for our needs so that we are more attuned with our environments.

Zeitgebers are those that send the signals to the body. When you eat at night, you are signalling that it is a time of eating, not of sleeping and digestion needs to happen when it would normally be shut down. Melatonin is a hormone your brain secretes in darkness to promote sleep and blue light is a melatonin-suppressant, signalling it’s time to be active. When you use light as the guide, digestion is appropriate, and sleep is timely. This is a system that has primal roots in our need to use optimal sunlight for our functioning as hunter-gatherers, and instinctively we use this cycle to feel safe. If you’re working a night shift or into late nights or are in a tube lit room or cubicle without ventilation and access to daylight, your instances of stress, irritability, anxiety are prone to be higher naturally.

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How to set your circadian rhythm

Typically, once a circadian rhythm is set, it is pretty hard to change. This is what we mean when we say, ‘I am a morning person’ or ‘I am a night person’. One way to set it, is to sleep and wake up at the same time every day.

Another would be to use the zeitgebers – sleep, food, social interaction, body temperature, physical activity – to signal when it is day and when it is night. When we systematise our habits to night and day schedules, then the body finds it easier to fall asleep and wake up, it knows when to ramp up activity and when to shut it down.

Daylight increases the cortisol in the body. You may have heard the term cortisol when referring to or checking the stress levels. High cortisol indicates stress but what cortisol is, is an agent of movement. As it rises, you need to use it for momentum. So as the body releases the hormone, it's the right time to use it to exercise, go for a walk, put it to use to get the system pumping. Cortisol that doesn’t get used is what goes to the belly and sits there accumulating fat. Using the energy as it is released and at the appropriate time is the best way to utilize the body to its optimal energy cycles.

Exposure to sunlight

The ancient Chinese systems of Tai Qi and Qi Gong, Indian yoga asanas such as the Suryanamaskar or simply spiritual sun salutations, offering water to the sun, prayers to the sun, etc., are prevalent in all indigenous systems. Apart from being a conscious gratitude practice (which releases dopamine and serotonin, which aid in emotional self-regulation), these are practices that allow us to raise our levels of activity with the sun’s rays. Waking to the sunlight, allowing ourselves to ease into the day as the sun’s rays gain strength and increasing activity proportionately are important to feel aligned. For instance, if you’re an early riser, don’t drink your coffee before the sun is well up, allow the sleep to lift naturally by heading out for a gentle walk. It will be far more effective in utilizing your energy levels. Don’t exercise late at night, it will affect your sleep cycles and your eating cycles. That’s how you end up popping supplements such as melatonin instead of allowing your body’s natural secretions to govern your sleep.

Sunlight also boosts vitamin D and your general state of wellbeing, your ability to regulate your moods, and your energy. If your work shifts change or you fly across time zones frequently and you don’t have the option to shift your work hours, then try to use the sun wherever you are as an appropriate guide.

So, use lighting devices to mimic sunlight, use music and physical activity such as walking or standing a lot instead of being seated and sedentary to mimic the day, but also if you’re sleeping during the day, put the blinds down to mimic darkness and reverse the order of your night and day with some care.

How to use light for good health

1. Use the sun as a guide, your key zeitgeber – eat, move, sleep when the sun is up.

2. When active after sundown, minimise activity to light and relaxing levels (such as reading, or listening to soothing music).

3. Raise your activity level according to the strength of the sun.

4. Avoid caffeine, stimulants or intoxicants too early or too late in the day.

5. Systematise your schedule into day and night activities on a consistent basis.