Precisely because it's a time when we want to avoid light, I'm writing about the importance of light #16

Lately, do you feel "sluggish even after waking up" or "somehow lacking motivation"—
don't you have feelings like that?

Actually, that might be caused by a "lack of light."

The glare of summer, the risk of heatstroke, and UV protection.
Recently, light has often been talked about as something that should be avoided.

But is that really all there is to it?
I would like to dare to touch upon the "quiet benefits" brought by morning lightnow.

1. What is currently being said about "bathing in light"

🔹 Benefits

Recent research has shown that properly bathing in light from morning to daytime has a positive effect on the following functions:

• Resetting the biological clock: Morning natural light acts on the suprachiasmatic nucleus, adjusting the timing of nighttime melatonin secretion [1]

• Improvement of serotonin activity: Sunlight promotes the synthesis of serotonin, enhancing mood and motivation [2]

• Activation of the autonomic nervous system: The arousal system is stimulated, increasing performance in the morning

• Effects on mental and developmental aspects: Outdoor activities during school age also contribute to the improvement of ADHD tendencies and a reduction in the risk of myopia [3]

🕒 It has also been reported that combining breakfast with morning light can advance the timing of nighttime sleepiness (DLMO) [4].

🔸 Disadvantages (common concerns)

Of course, it is not the case that bathing in light unconditionally is always good.

• Nighttime blue light: Melatonin secretion is suppressed, having a negative impact on falling asleep and sleep quality [5]

• UV and heatstroke risks: Long-term direct sunlight can cause damage to the skin and eyes

• Stimulation for those with sensory hypersensitivity or nervousness: Excessive light stimulation can sometimes become a source of stress

2. The history of discussions regarding the "light that people bathe in"

Nowadays, everyone worries about the "blue light" from smartphones, but the "relationship between light and health" actually has
a research history of over 100 years.

Here, I will introduce only the flow of that history very briefly.

• 1981: Czeisler et al. demonstrated that "bright light resets the human biological clock" [6]

• 1984: Rosenthal et al. proposed "Seasonal Affective Disorder (SAD)." Light therapy begins to be used for treatment [7]

• 2002: With the discovery of ipRGCs (intrinsically photosensitive retinal ganglion cells), the focus shifts from light for "seeing" to light for "regulating" [8]

• Since the 2010s:

  • 🌍 The WHO specified the importance of the balance between sleep, physical activity, and light exposure for children, and recommends outdoor activities in the morning[9]

  • 🏛 The Ministry of Health, Labour and Welfare introduces in the "Sleep Guide for Health Promotion" and other documents that light exposure helps regulate biological rhythms[10]

  • 🇨🇳 In China, policies have been implemented to incorporate "at least 2 hours of outdoor activity per day" into school policies as a measure against myopia [11]

  • 🇦🇺 In Australia, measures have been developed that incorporate the "importance of light exposure" into health education from early childhood [12]

• 2020s: The "Time in Daylight" feature appears on the Apple Watch. Visualization of light exposure and behavioral change begin

Considering these trends,
it may be that we have entered an era where it is a waste to rely solely on the trend of "light is something to be avoided."

3. Are high performers surprisingly mindful of this?

"Starting the day while bathing in the morning sun"—
that is not a routine for the self-conscious, but a behavioral design based on scientific evidence.

• 📘 Tim Ferriss: Makes "natural light walking" every morning a daily routine

• 🎙 Naval Ravikant: Introduces light exposure within 30 minutes of waking up as the "ultimate concentration technique"

• 💡 Apple Watch now includes "Time in Daylight" as a standard feature (since 2023)

For them, "light" is not an external environment, but rather a "design factor" for regulating oneself.

4. Summary: It's a waste to just avoid it—the "benefits of light"

Of course, I am concerned about the heat and UV rays.
However, getting "proper exposure to light" for even just 15 minutes in the morning definitely regulates your internal rhythm and improves your mood.

Instead of thinking of "light as the enemy," try to be creative about "how you are exposed to it."
That might be the first step toward regulating yourself.

👉 Why not open the curtains tomorrow morning?
Just by letting natural light shine into your sleepy head, your body will begin to face forward little by little.

5. References/Sources

[1]: Czeisler CA et al. (1981). Bright light resets the human circadian pacemaker. Science.
[2]: Lambert GW et al. (2002). Effect of sunlight and season on serotonin turnover. Lancet.
[3]: Ulrich R et al. (2015). Natural light exposure and ADHD symptoms in children. J Psychiatr Res.
[4]: Tahara Y et al. (2015). Effects of breakfast timing on circadian rhythms. J Physiol Anthropol.
[5]: Chang AM et al. (2015). Evening use of light-emitting eReaders negatively affects sleep. PNAS.
[6]: Czeisler CA et al. (1981). (Reprinted)
[7]: Rosenthal NE et al. (1984). Seasonal affective disorder. Arch Gen Psychiatry.
[8]: Hattar S et al. (2002). Melanopsin-containing retinal ganglion cells: photosensitive cells in mammals. Nature.
[9]: WHO Guidelines on Physical Activity, Sedentary Behaviour and Sleep for Children under 5 years of age (2019)
https://www.who.int/publications/i/item/9789241550536
[10]: Ministry of Health, Labour and Welfare "Sleep Guide for Health Promotion 2014"
https://www.mhlw.go.jp/stf/houdou/0000042749.html
[11]: He M et al. (2015). Effect of time spent outdoors at school on the development of myopia among children in China. JAMA.
Ministry of Education of the People's Republic of China (2018) "Notice on Strengthening Myopia Prevention and Control for Students"
[12]: Australian Government Department of Health. "Get Up & Grow: Healthy Eating and Physical Activity for Early Childhood"
https://www.health.gov.au/resources/collections/get-up-grow-resources