The Nexus between Sunlight Exposure & Sleep

Dr. Manal Ghazzawi, BPharm (Hons), Pharm D, FPCP, MPH

By: Dr. Manal Ghazzawi, BPharm (Hons), Pharm D, FPCP, MPH

Why is sunlight so important to the human body?

Let’s go to the cellular level. Every cell in our body has a mitochondrion which is the machinery or powerhouse in our body that produces energy. The mitochondria take the food that we eat and transform it into energy. However just like every machine it can overheat, shut down and produces a byproduct called oxidative stress which are oxygen radicals! When oxidative stress builds up too much, it can cause lots of problems that could lead to less optimal health causing inflammation, cancer, dementia, diabetes, learning disabilities and even COVID-19 mortality. When oxidative stress builds up in the mitochondria, there’s a cooling system which occurs day and night. There is a fascinating chemical which is activated to be produced to reduce oxidative stress in the mitochondria, interesting right? This chemical is called melatonin, produced in our brain both at night and during the day, it is one of the strongest antioxidants, twice as potent as vitamin E. According to a published paper in 2019, by Professor Scott Zimmerman, it was highlighted that melatonin produced in the mitochondria to reduce oxidative stress, may play a role in the prevention and/or treatment of Alzheimer’s and Parkinson’s disease.

At night melatonin is produced in the brain, enters the blood stream, and then goes into every cell of our body to mop off the oxidative stress produced by the mitochondria. We can say this is how the body gets rid of oxidative stress at night and we are able to sleep. Any form of light at night, exposed to our eyes can shut down melatonin production from the brain. During the day, there is a completely different system that stimulates the production of melatonin to combat oxidative stress. At day time, melatonin production in the mitochondria is stimulated by near infra-red radiation (NIR) from the sun. This is a new scientific discovery which makes us rethink as to how much sunlight we are getting, and what happens if we don’t get enough?! It is important to understand that melatonin produced by our brain at night (Hormone of Darkness) helps us sleep, and the melatonin produced at cellular level inside the mitochondria, this is stimulated by sunlight (hormone of daylight) play different roles – which has nothing to do with sleep at all! Mind you the above effects do not occur with melatonin supplements that you might be taking, melatonin supplements just go directly to your blood stream and tell the body to sleep.

How do humans interact with light?

One way we can explain our interaction with light is through the circadian rhythm (CR). CR is a 24-hour cycle that is part of the body’s internal clock, running in the background to carry out essential functions and processes. The CR regulates our body temperature, helps in production of melatonin, and many other chemicals that are essential for our body functions. According to the CR, melatonin production starts at 9 pm and that is the time you would want to avoid bright light exposures to prevent shutdown of melatonin production. Consequently, is it very important that the CR is in sync, and it is well regulated. There is scientific evidence to prove that dysregulation of the CR, can cause induced sleep wake misalignment which in turn can cause unscheduled production of insulin and other hormones, circadian misalignment due to sleep deprivation can induce production of inflammatory markers and insulin resistance which is a main culprit in type 2 diabetes (Scheer et al.). Disruption of the CR can cause stress hormone production at a rate which can be associated with anxiety and depression during the day.

One way to allow the CR to align with what goes on outside your body and to help you sleep at night is by avoiding screen time or bright lights during bedtime, as this could shut down the production of melatonin and leads to insomnia. In other words, avoid using laptops, phones at the time you are supposed to be sleeping. If you need to work at night with your laptop avoid screen time at least 2 hours before bed. In addition, if you are awake before bedtime, it is inevitable that you need some lighting but let it be low on the floor below your visual field and as dim as possible. Orange or red dim light below your visual field could also be better if you need to have light in your room.

Why should we be happy with a sunny weather or Salone’s beautiful weather?

If you have lived abroad in a country long enough during winter, you will learn to appreciate and long for sunny weathers. You will appreciate sunlight even if it is freezing cold, you will feel rejuvenated to see the sun shining bright while you are outside. The sun actually elevates your mood, for this reason people experience seasonal affective disorder during the winter season, and women are more prone to be depressed during winter than men according to studies. In a meta-analysis, it was proven that exposure to bright light during the day between 15 minutes to an hour for 4 weeks improved mood, hence reduced seasonal affective disorder.

To anchor the circadian rhythm or to set it right, NIR sunlight exposure should be done before 9am in the morning ranging between 30 sec to 30 mins. Wearing sunglasses will limit kick starting the CR accordingly. The brighter the sunlight the shorter time you need to spend outdoor, if it is a cloudy day up to 30 mins exposure will be needed. NIR penetrates your clothes deep into the skin/body and can be perceived as heat. Sunscreens can only block ultraviolet radiation but not NIR. When we say sunlight exposure, sitting in your car driving somewhere does not count, it is about really getting outside in the open; direct sunlight exposure I mean. Notwithstanding that, interestingly, you can still be in the shade and get NIR exposure because leaves of trees reflect the latter. Sunlight exposure is safest before 10 am and after 3pm. The more time spent under direct sunlight the more Vit D will be produced by the skin through ultraviolet B (UVB) radiation.

Environmental research published in 2018, demonstrates that spending time and living close to natural green spaces reduces the risk of type2 diabetes, cardiovascular diseases (heart and blood vessel diseases) and premature death. People living closer to nature have reduced blood pressure, heart rate and stress. Exposure to light or sunlight improves subjective wellbeing, cognitive performance, reduces depressive disorders and cancer. In fact, the World Health Organization classifies CR disruptive work shift, as a probable carcinogen (cancer-causing agent).

To cut matters short, go for a walk every morning; enjoy Mother Nature’s sunlight while you can, to live a healthy and prolonged life! Rely on sunlight to naturally produce melatonin, get your CR on sync to help you sleep like a baby!


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