How often do you think about the type of light that exists in our modern day world?
Do you know that different types of light have different effects on how well we sleep during the night and how energetic we feel during the day?
Scientific research has shown that the type of light we are exposed to plays important roles in maintaining our health.
In this post, we discuss how people have evolved to live in day-night cycles. Why is it important to behave in ways that ‘obey’ the natural sleep-wake cycle?
Next, we focus on blue light and we discuss how the blue light spectrum influences our body’s physiological processes. Why are the effect of blue light especially important to learn about?
Last, we discuss optimizing the type of light we are exposed to using blue light blocking technology. What are the scientific discoveries about the benefits of blocking blue light as a health strategy?
Part 1: Natural Sleep-Wake Cycles
The circadian rhythm is the body’s physiological mechanism that regulates energy levels, metabolism, and feeling awake or tired during each day.
To understand why it is important to optimize our sleep-wake cycle, first let’s review how humans have evolved to function in 24 hours day-night cycles environments.
1.1 Melatonin – The Sleep Hormone
The hormone melatonin is the most researched mechanism by which our body regulates our circadian clocks .
During the day, natural light provokes the body to suppress melatonin production leading to lower melatonin concentrations and people feeling awake and alert.
Due to decreased light exposure in the evening and at night, melatonin concentrations steadily increase and this causes sleepiness. When melatonin is administered in people, it promotes earlier onset of sleep and extends sleep duration.
When melatonin is administered in people, it promotes earlier onset of sleep and extends sleep duration . Among the other important findings
Why is it important to learn the basic role of melatonin in regulating our sleep-wake cycles? The answer is because
Evening-time exposure to light also shifts the circadian clock to a later time . Combined, these two effects make it more difficult to fall asleep at night!
Last, exposure to light also strongly increases brain alertness at night – further making it more difficult for people to fall asleep .
1.2 Importance of Restful Sleep
How long we sleep is an important factor in our journey towards optimal health.
Not sleeping enough (aka. sleep deficiency) is a considerable risk factor for several chronic conditions including:
On the flip side, there is also convincing research evidence that sleeping longer than 9 hours per night is also associated with adverse health effects . However, in modern 24/7 societies sleeping too little is a much bigger problem compared to sleeping too much.
Data from the National Health Interview Survey demonstrate the degree to which people are missing restful sleep
|Sleep Duration (occurrence in %)||Year 1977||Year 2009|
|Very Short Sleep|
(less than 5 h / night)
|1.7 %||2.4 %|
(5 to 6 h / night)
|19.7 %||26.7 %|
|Too much sleep|
(more than 9 h / night)
|11.6 %||7.81 %|
The table clearly demonstrates that not sleeping enough is becoming more common, while oversleeping is becoming less common in today’s fast-paced world. Adapted from: 
Recently, a large meta-analysis study, conclusively showed that short sleep influences cardio-metabolic factors and does have an adverse effect on longevity (increases overall mortality in people) .
Part 2: Blue Light Matters More Than Other Wavelengths
Different light wavelengths have different effects on our body. The difference is determined by the signals our eyes send to our brain – as a response to the type of light registered by the retina zone in our eyes.
Blue light is a specific type of light at 400-780 nm wavelength in the visual spectrum. The effects of blue light on our overall health are well researched and useful to learn about in terms of striving towards optimal health.
2.1 Health Effects of Excessive Blue Light Exposure
Of all wavelengths of light, blue light carries the highest amount of energy per photon – meaning per unit of light. Researchers started to study the effects of blue light because of the scientific likelihood that blue light has the potential to cause photochemical damage to the retina zone in the eyes .
Common sources of blue light include the sun and artificial light sources such as light-emitting diodes (LED lights) or fluorescent light tubes. Combined, these sources emit the amount of blue light that is nearing the internationally set limits for blue light exposure .
In addition, results from cell experiments with animals and cells suggest that as the eyes age, the eyes become even more sensitive to damage caused by blue light .
Researchers have already studied the molecular mechanism leading to damage in
2.2 Blue Light Exposure During The Day Is Healthy
We already discussed how evening and nighttime exposure to blue light negatively influence our body’s ability to fall asleep and how important it is to get enough restful sleep during the night. We also discussed how sleep shortage compromises our overall health status.
However, being exposed to enough blue light during the day is just as important as avoiding blue light during the evening dark hours of the day. In a study set in workplace environments, artificial office light enriched with blue light led to improvement in self-reported alertness and employee sleep quality at night . This makes sense – by inhibiting melatonin release during the day, blue light stimulates our brain to remain alert and focused during
In addition, exposure to blue light during daytime:
- improves our ability to discriminate colors 
- allows us to see better when nighttime arrives 
- improves our working memory (better performance at tasks) 
3 Blue Light Blocking Technology
How to achieve a more balanced personal sleep-wake cycle?
As a general rule of thumb, you should strive towards more blue light exposure during daytime and less blue light exposure in the evening and, especially, during night. Sunlight is the best light for optimal health!
Another good rule of thumb is to get some sunlight during the daytime hours – even 10 min open-air walk matters in terms of getting natural sunlight (which also contains blue light).
Last and maybe most important – get enough hours of sleep during each night. Remember that not sleeping enough is a modifiable factor that strongly influences our overall health.
Next, we discuss how to block blue light on your mobile screen during night hours. If you find yourself in a blue light rich environment during the evening or night (for example office or staying up late at home), we also discuss how blue light blocking glasses are a good strategy for optimal health.
3.1 Block Blue Light on Mobile Phone Screens
Devices that contain LED – backlight displays are rich in blue-light emission. To produce normal looking white light in the background, electronic devices emit light at short wavelengths – including wavelengths in the blue light range.
The popularity of LED smartphones, portable tablets, and computer screens
Compared to non-LED screens, 5 hours exposure to LED computer screens during evening hours lowers melatonin levels . The research team behind this study also discovered that although melatonin levels were rising during the evening (as expected), melatonin did not rise as steeply when compared to participants in the study who remained in more dark environments during evening hours .
Researchers have also discovered that 2 hours – or longer – exposure to tablets with blue light screens results in significantly lower melatonin levels in participants .
The good news is that the manufacturers of electronic devices have begun to implement tactics towards delivering healthier screen time to users.
At this time, it is a good idea to check for yourself whether your
Since a few years ago, major companies such as Google, Samsung, and Apple have started implementing blue light blocking technology in their electronic devices.
Today, numerous phone models allow you to set blue light parameters including
Mobile Phones With Blue Light Settings
3.2 Blue Light Blocking Glasses
Scientists refer to
Blue light filtering lenses are particularly useful in terms of filtering the high-energy wavelengths of light without having a negative impact on visual performance and quality of sleep at night .
Results from previous laboratory studies show that reducing blue light exposure by 50% could reduce approximately 80% of blue