April 16, 2015
A Dark Night Is Good For You
That's right, darkness is your friend. We already know that most of us aren't getting enough sleep and it is great that we are paying attention to that and trying to change it but the need for dark is still mostly ignored.
Being exposed to regular patterns of light and dark regulates our circadian rhythm. Disruption of this rhythm can increase your risk of developing health conditions like obesity, diabetes and breast cancer.
The physiological processes that control our sleep and wake, hunger, activity levels, body temperature, melatonin level in the blood (to name only a few), are called endogenous circadian rhythm.
The endogenous circadian rhythm is nearly, but not quite, 24 hours. This rhythm has evolved with us and is deeply connected to our genetic make up. Our bodies rely on the sun to reset this cycle making light and dark very important signals.
During the night, in the dark, our temperature lowers, metabolism slows and melatonin rises. When the sun rises, melatonin drops and you start to wake up.
If you were to put someone in a dark cave, without any light, the cycle would last close to 24 hours. But over time, without any time cues from the sun, the person would become out of sync with the people outside the cave. In fact, many profoundly blind people -- those who cannot perceive light, must deal with this lack of synchronization on a daily basis.
Not all light is created equal, some make you more awake and alert while others have little effect.
Light from the sun is a strong blue (although it does contain other colours) and this is important in the morning when you need to be alert. But when it comes to the evening, blue light is not good. It tricks our bodies into thinking it is daytime and we know that bright blue light has the strongest effect on lowering melatonin.
Your tablet, phone, computer or compact fluorescent lamp (CFL) all emit blue light. Using these things at in the evening can prevent your natural physiological transition to night making it harder to sleep and increasing your long term risk for poor health.
Red and yellow lights, like that from a candle or a campfire, have little effect on these transitions.
Light regulates our sleep and wake patterns
The physiological processes that control our sleep and wake, hunger, activity levels, body temperature, melatonin level in the blood (to name only a few), are called endogenous circadian rhythm.
The endogenous circadian rhythm is nearly, but not quite, 24 hours. This rhythm has evolved with us and is deeply connected to our genetic make up. Our bodies rely on the sun to reset this cycle making light and dark very important signals.
During the night, in the dark, our temperature lowers, metabolism slows and melatonin rises. When the sun rises, melatonin drops and you start to wake up.
If you were to put someone in a dark cave, without any light, the cycle would last close to 24 hours. But over time, without any time cues from the sun, the person would become out of sync with the people outside the cave. In fact, many profoundly blind people -- those who cannot perceive light, must deal with this lack of synchronization on a daily basis.
What does your body do in the dark?
Your body does a lot in the dark. Levels of the hormone leptin, which control hunger, go up meaning you don't feel hungry. Why does this happen? Having evolved without artificial light at night, one theory says that leptin goes up at night because it was better to not be hungry at night, meaning we didn't have to forage in the dark when the risks would be far greater than during the day. In the last several years, it has become clear that the genes that control endogenous circadian rhythm also control a large part of our entire genome. This includes genes for our metabolism (how we process the food we eat), DNA damage response (how we are protected from toxic chemicals and radiation), and cell cycle regulation and hormone production (how our cells and tissues grow). Light at night messes all this up. Exposure to electric light at night has biological links to common modern day diseases like diabetes, obesity, cancer and depression.Blue light, red light, no light
Not all light is created equal, some make you more awake and alert while others have little effect.
Light from the sun is a strong blue (although it does contain other colours) and this is important in the morning when you need to be alert. But when it comes to the evening, blue light is not good. It tricks our bodies into thinking it is daytime and we know that bright blue light has the strongest effect on lowering melatonin.
Your tablet, phone, computer or compact fluorescent lamp (CFL) all emit blue light. Using these things at in the evening can prevent your natural physiological transition to night making it harder to sleep and increasing your long term risk for poor health.
Red and yellow lights, like that from a candle or a campfire, have little effect on these transitions.