Key takeway 1 : Moonlight, candles and fireplaces don't impact your circadian rythms

Intensity and wavelengths of those light sources are such that they don't impact our circadian rythms. Plus, the sensitivity of the cells located in the eyes that react to light to set the circadian rythm adjust their sensitivity throughout the day i.e. they are less sensitive at the end of the day.

Key takeway 2 : Use of red light is unnecessary and most red light devices are too bright to be used at night

Some equipment producing red lights exist. However, they produce too bright of a light to be used at night without disrupting the circadian rythms.

Key takeway 3 : Blue blockers don't save you at night

You need blue light during the day. So don't wear blue blockers during that time.

And at night, even with blue blockers, seeing intense lights will disrupt the circadian rythms (roughly between 10pm and 4pm). So at night, avoid all bright lights even with blue blockers (in other words, blue blockers are useless).

Key takeway 4 : Only light to the eyes matter to set circadian rythm

A few commercial products claim that light introduced by the ears or the nose or the mouth can impact the circadian rythms.

Until serious studies are done, this is not considered as true and only light provided through the eyes can set circadian rythms.

Key takeway 5 : Viewing light through a windows takes forever to impact the circadian rythm

Viewing light through a window is inefficient as the intensity of light (measured in Lux) is drastically diminshed.

Plus, it does not scale linearly. So half the lux DOES NOT MEAN you can just stay twice longer and get the same effect. It does not work that way.

So to set-up your circadian rythm, get outside.

Key takeaway 6 : Prescription glasses are fine

Prescription glasses are fine since they focus light to the eyes. Contrarily to windows or windshield that scatter light.

Key takeaway 7 : Add-up your lights early in the morning before the circadian dead zone

Adding-up light works during the early morning (few hours after sunrise). So, if you live in a low light period, get oustide longer during the morning. Set-up bright lights, especially overhead, when inside again during the morning. These lights will add-up and help set-up your circadian rythm.

After these few hours in the morning, you will be in a circadian dead zone and won't be able to change your rythm even with bright lights.

Key takeway 8 : Viewing light at sunset helps your body to "shield" against other lights at night

Viewing the light at sunset (again … from outside) helps prepping the body for sleeping. And somewhat provides a protection against other lights (e.g. TV, screens, …) that one will still be subject to after sunset.

Key takeway 9 : Seasonality is important

Seasonality regulates body mechanisms. During winter, less light is received by the cells. Therefore, the melatonin signal will be stronger and this tends to downregulate some mechanisms like reproduction, protein synthesis, fat oxidation, … And also people tend to be more depressed in winter. The contrary is true during summer.

In other words, it's logical to be (and feel) less in shape in winter than summer. Obviously, not everyone reacts the same way or shows the same sensitivity to seasonality. But it's a real thing.

Key takeway 10 : You can't just bathe in light

Based on key takeaway #9, one could think that bathing in sunlight all day long during winter could prevent strong melatonin signal and therefore prevent seasonal depression.

But melatonin has other effects and benefits e.g. stimulating the immune system. Therefore, one can't just stay exposed to light all day long because this would have adverse effects on other necessary systems.

In summary, everyone will need to determine how much light he needs during the day and how much light he can tolerate at night to have an optimal system.

Key takeway 11 : Golden timings for exercising

Litterature suggests that 30 minutes, 3 hours and 11 hours after waking-up are windows of opportunity for exercising and performance.

However, exercising at other times is better than nothing.

Key takeway 12 : Pavlovian tricks for neuroplasticity

Hearing a tone or smelling an odor during learning and having that stimulus repeated during the nights significantly increases the learning rate. Tactile stimulus e.g. vibrations on the wrist should also provide similar gains in learning rate improvement.

Key takeway 13 : Increase learning efficiency by taking naps

Short 20 minutes naps or non-sleep deep rest protocols (e.g. yoga nidra) following an intense learning bout (whatever the learning was : intellectual, music, movement) of 90 minutes have shown to increase both the amount of information retained as well as the depth of retention.

Key takeway 14 : Your temperature matches the daytime

If circadian rythms are correctly tuned, the body temperature shall match daytime. And it matters a lot because body temperature triggers various things like a rise in temperature promotes ability/desire to engage in an activity (learning or physical).

If someone has not slept very well the day before and experiences a morning chill by 11am, it's because its body temperature really is low and promotes sleepiness.

Key takeway 15 : Cold shower early in the morning shifts advance your clock

Taking a cold shower early in the morning will wake you up (duh!) for sure. But more importantly, it will phase-advance the internal clock i.e. one will want to wake-up earlier.

This is because there is a rebound after an ice bath causing thermogenesis i.e. an increase in body temperature.

Key takeway 16 : Eating schedule influences wakefulness or sleepiness

A fasting state tends to promote wakefulness (think : being active to search for foods) while a good meal tends to promote sleepiness.

Particularly, a protein-rich meal tends to promote tryptophan, therefore serotonin and therefore sleepiness (rather read : happy with current situation).