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Sunlight is the most important environmental cue for daily human activity and for setting our biological clocks. Our biological clocks run on a 24-hour cycle called a Circadian rhythm. One of the most important and well-known circadian rhythms is the sleep-wake cycle. But did you know that each of the body's individual cells contains its very own biological clock, whose rhythm is entirely gene coded?
Located just behind the bridge of the nose is a tiny region of the brain in the hypothalamus called the suprachiasmatic nucleus or (SCN). The SCN serves as the central control room for all our biological clocks; it oversees all of the body's time-activated processes.
When a light stimulus hits the retina of the eye a signal travels to the SCN and then onward to the brain's pineal gland, the gland responsible for the production of melatonin. This interaction between the SCN and pineal gland, affects our sleep cycle and other functions that show circadian rhythmicity like: physical activity, alertness, hormone levels, body temperature, immune function, and digestive activity. The SCN coordinates these rhythms across the entire body and in addition it regulates gene expression in specific tissues.
Visible light comes in different wavelengths that dictate the color –just like a rainbow the light spectrum goes from violet (ultra-violet light) to red (infra-red light). Shorter wave lengths are violet/ blue and red is the longest. With natural sunlight are brains are exposed to the full spectrum of light. At sunrise there is red and blue light in the sky. At mid-day it is all blue and at sunset red returns until there is complete darkness.
This pattern of light signals different activities in the brain. For example, in the morning at sunrise, the combination of red and blue light signals the body to make hormones, which are essential communication molecules. Hormones get released into the blood and travel to distant glands throughout the body instructing those glands to make hormones. For example, the adrenal gland is instructed to make and release the hormone, cortisol.
Morning light signals the brain to release cortisol, which is our wake hormone. Cortisol wakes us and should be at its peak in the morning. Melatonin is our sleep hormone or the hormone of darkness and is released at night time in an opposite relationship. Cortisol levels are highest at 6am and lowest at midnight. Melatonin levels are highest at 3am and lowest at mid-day.
When the eye sees blue light in mid-day that color of light sends a message to the brain to stop producing hormones and therefore the production of hormones in other glands is also turned off. This ensures that hormone production factories are not running 24/7 and overly taxed.
When the sunsets and light disappears that signals the brain to release melatonin which encourages sleep. Proper light and darkness cycles are required to help us sleep.
Sleep is essential for our health. It gives the brain time to brain repair, restock, and reenergize. It is during sleep that debris from the daily brain functions and activities is cleaned up. There is a layer of piping that surrounds the brain’s existing blood vessels called the glymphatic system. During sleep the space between brain cells increase this allows the brain via the glymphatic system, to flush-out debris and toxins that build up during waking hours. Without sleep debris piles up and actually damages the brain.
Therefore sleep is essential to regulate the circadian rhythm; the time clock of the body and to allow clean up from the daily activities as well as a time to consolidate memories and reflect upon what the brain learned that day.
Quality sleep is essential to brain health!
Wearing blue light blocking glasses at night can mimic the proper light exposure which should be red light fading into darkness. This tells the brain it is time for sleep and time to release melatonin, which helps regulate the sleep cycle.
Chronic exposure to blue light at night interferes with our natural circadian rhythm and the signal to turn off hormone production protecting them from being depleted too quickly.
It is important to NOT have continued exposure to blue light at night.
Our circadian cycles regulate our energy levels, performance, metabolism and our recovery. Regular exposure to cycles of natural light is required to synchronize these circadian rhythms. Unfortunately most of us don’t get enough natural light during the day and get too much artificial light at night. Studies show that artificial light at night disrupts our circadian rhythms and thereby increases the risk of insomnia, depression, cancer, diabetes, and cardiovascular disease.
Sleep deprivation can alter the function of up to 711 genes, including some involved in stress, inflammation, immunity and metabolism. We depend on genes to produce a constant supply of proteins for replacing or repairing damaged tissues and they stop working after just a week of poor sleep. Insomnia alters the function of the immune system and impedes the metabolism and absorption of nutrients. A lack of sleep affects your ability to heal!
Emergent research confirms that our sleep habits have a direct impact on the composition of our gut bacterial colonies. When we don’t get enough rest, the health and diversity of our microbiome suffers.
Scientists even suggest that the microbiome is the link between sleep deprivation and mental decline. When we don’t get enough sleep, imbalance in our guts causes inflammation in the brain which manifests as anxiety and depression and contributes to the eventual development of dementia and Alzheimer’s.
Get quality light and sleep!
Manage your circadian rhythms by trying to expose your eyes to changing natural light intensities. You might have to wake earlier and step outside to watch the sunrise. Get outside at lunch time so your eyes are exposed to natural blue light. At night time limit as much exposure to artificial blue light as you can. This is especially important if you are having a difficult time falling asleep.
At night turn off as many LED lights as you can. Consider using candlelight as that is natural red light. Limit your use of computer screens and cell phones that emit blue light. You can mitigate blue light exposure from you computer by downloading an App called f.lux. This app changes the light intensity on your computer screen. It warms up your screen at night to help you relax and wind down before bed.
You can also change your iPhone screen to red at night by triple-clicking the Home Button. Follow the instructions on the link below.
Red light is a healing frequency of light and when used correctly could provide health benefits. Red light stimulates the production of collagen; it can help with joint pain and aid in muscle recovery. The frequencies of light with the most proven benefits are 660 nm visible red light and 850 nm invisible infrared light. These are the two frequencies to look out for when purchasing a red-light therapy device. Red light also has the ability to stimulate ATP production and ATP is energy! For further information click on the link below.
Consider purchasing blue light blocking glasses. Make sure you get quality glasses that truly block the short wavelengths of 400 nm to 500 nm of blue/green light. Check out this website that have quality glasses.
These glasses are great to use if you are on the computer at night or if you like to read with your ipad.
TV screens emit blue light but because you generally sit a fair distance from the screen that helps mitigate exposure. This is not the case if you are watching movies on your laptop at night! Blue light blocking glasses would be beneficial in this situation as you are so close to the screen.
You need to make sleep a priority! The best way to set your circadian rhythms is to practice good sleep hygiene. Good sleep hygiene is all about putting yourself in the best position to sleep well each and every night. For tips on how to improve your sleep hygiene check out the link below.
It is a misconception that being a morning or evening person is a “choice”. It's our genes that predetermine whether we'll be early birds or night owls. We can tweak our natural programming, but not by more than two hours in either direction. Everyone’s circadian rhythm is slightly different.
Dr Michael Breus is a clinical psychologist and a sleep expert. He has taken circadian rhythms one step further. He has come up with four classifications called sleep chronotypes. Based on morning and evening preferences, he identified four different chronotypes, or circadian rhythm personalities, and then associated each one with an animal whose sleep-wake habits best mirrored them.
When Dr Breus switched up his patients’ daily routines to accommodate their sleep chronotype, their productivity soared and several sleep issues resolved.
Understanding your particular sleep chronotype could help you figure out the best time of day to make an important decision, work out, and do anything better.
It’s easy to learn your chronotype by taking this quiz: www.chronoquiz.com.
For more information from Dr Breus Phd checkout his website. He is also a good resource for sleep supplement information.
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