• Light and Darkness Affect Your Health and Wellbeing

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    If you don’t sleep well, you’re not going to be optimally healthy no matter how good your diet and exercise are. To maintain and “anchor” your master clock, you want to get bright outdoor light exposure for 30-60 minutes a day, ideally at solar noon. Sleep in maximal darkness. Blackout shades or a sleep mask is recommended.

    By Dr. Mercola

    While it may not be immediately obvious as to why, light is actually crucial to your health. I've always believed that you could have the ideal lifestyle with respect to the food you're eating, the water you're drinking, and exercise, but if you don't sleep well, you're just not going to be optimally healthy.

    Poor sleep inevitably leads to health problems. Maintaining a natural rhythm of exposure to daylight, and darkness at night, is an essential component of sleeping well.

    Researcher Dan Pardi works with the Behavioral Sciences Department at Stanford University and the Departments of Neurology and Endocrinology at Leiden University in the Netherlands 

    “I look at how sleep deprivation, or not getting enough sleep or the amount of sleep that you need, can influence decision making and cognitive processes like reaction time, memory, impulsivity, and how that relates to food choice,” he explains.

    He’s also the CEO of a health-behavior technology company called Dan’s Plan, which seeks to help people optimize their health by establishing and sustaining an effective daily health practice, which includes maintaining good sleep habits. 

    How Much Sleep Do You Really Need?

    Your sleep requirements change across your lifespan. Most infants will sleep a good percentage of the day. By adulthood, the amount of sleep typically settles somewhere around seven to nine hours. According to Pardi, the average, across a sample population, is about eight hours of sleep per night.

    That said, sleep requirements are highly individual, and can change from one day to the next, depending on factors like stress, physical exertion, illness, pregnancy, and so on.

    With so many variables, figuring out your optimal sleep requirement is a bit like a moving target. So, how can you tell you’ve achieved enough sleep? According to Pardi, the following three factors are key to determining how restorative sleep is

    • Duration— The number of hours you sleep
    • Timing—i.e. going to bed at approximately the same time each night. Even if the duration of sleep is the same, when the timing of your sleep is shifted, it's not going to be as restorative
    • Intensity—This has to do with the different stages that your brain and body goes through over the course of the night; the sequence of them, and how those stages are linked. Some medications will actually suppress certain phases of sleep, and certain conditions like sleep apnea will lead to fragmented sleep. With these scenarios, even if a person is sleeping for an adequate duration and has with consistent timing, sleep is not as restorative 

    How to Improve the Quality of Your Sleep

    As mentioned earlier, the quality of your sleep has a lot to do with light, both outdoor and indoor lighting. The reason why light is important is because it serves as the major synchronizer of something called your master clock. This master clock is a group of cells in your brain called the suprachiasmatic nuclei (SCN). 

    As a group, these nuclei synchronize to the light-dark cycle of your environment when light enters the eye. You also have other biological clocks throughout your body, and those clocks subsequently synchronize to your master clock. 

    Exposure to Light Before Bedtime Hinders Sleep

    Among other things, melatonin acts as a marker of your circadian phase or biological timing. In a nutshell, this hormone influences what time of day or night your body thinks it is, regardless of what time the clock on the wall displays. Somewhere between 50-1,000 lux is the activation range within which light will begin to suppress melatonin production. Melatonin is a regulator of your sleep cycle, and when it is suppressed, there is less stimulation to promote sleepiness at a healthy bedtime. This contributes to people staying up later and missing valuable sleep! 

    One 2011 study[i] compared daily melatonin profiles in individuals living in room light (<200 lux) vs. dim light (<3 lux). Results showed that, compared with dim light, exposure to room light before bedtime suppressed melatonin in 99 percent of individuals, and shortened the time period when the body has an elevated melatonin level by about 90 minutes. Furthermore, exposure to room light during the usual hours of sleep suppressed melatonin by more than 50 percent. The authors concluded that:

    “These findings indicate that room light exerts a profound suppressive effect on melatonin levels and shortens the body's internal representation of night duration. Hence, chronically exposing oneself to electrical lighting in the late evening disrupts melatonin signaling and could therefore potentially impact sleep, thermoregulation, blood pressure, and glucose homeostasis.”

    Simply closing your eyes is not enough as light can penetrate your eyelids. Aim to make sure your bedroom is very dark. I recommend installing blackout shades for this purpose. A far less expensive alternative is to use a sleep mask to avoid disrupting your melatonin production and circadian rhythm. Also keep in mind that digital alarm clocks with blue light displays could have a detrimental effect.

    Tracking Sleep to Maintain Mindfulness of Your Sleep Practice

    As discussed, getting the right light exposure across the day, evening, and night is crucial to helping you get regular deep sleep and to support robust wakefulness during the day. It takes time to experience the maximal benefit of proper light exposure. You need to have the right light at the right time for multiple days in a row to experience the full effect. However, as we introduced in the beginning, duration and timing of sleep also impact sleep quality and daytime performance. In our modern world – due to a large amount of forces of the modern life –

    Pardi says, it’s easy to both get less sleep than you need and to have too much variability in when you sleep.  To solve this problem, he created a free sleep tracking tool (video description) on his website ( that uses effective behavioral techniques to keep you mindful of how you’re living day by day. Making this sort of tool a part of your daily routine can lead to the addition of 30 extra minutes of sleep per night. If you’re like most people, and you’re getting insufficient sleep on a regular basis, these 30 minutes per night are a huge benefit. Practiced over time, the difference is equivalent to you missing 22 complete nights of sleep over 1 year! 

    There are several new devices that provide feedback on sleep quality. However, it’s normal for sleep to adjust itself every night so this sort of feedback – unless your diagnosing a sleep issue – isn’t really necessary. At worst, it’s misleading. A better use of these new technologies should aim to help you maintain the behaviors that help you get good sleep, like getting into bed at the right time. If I were to tell you that your sleep efficiency score from last night was 85%, what does that mean to you? Is that good, bad, or normal?

    On the other hand, if the tool were to remind you that your target bedtime is, let’s say, 10:45p, but you’re going to bed on average at 11:30p recently, now you have increased mindfulness and a clear goal for what you can do tonight to get the sleep you need. That’s very useful, especially since there are many temptations that make missing sleep easy. This sort of tool helps you fight back, making the right sleep behavior more visible and salient in your day-to-day lifestyle. Tracking, therefore, is useful for both the novice and expert alike, because regardless of you level of knowledge of the sleep science, mindfulness of your own daily sleep practice helps you maintain a healthy pattern long term, and that’s what counts in the end.”

    Bottom line:

    It’s challenging to get the sleep you need in the modern world. To get the sleep that helps keep you healthy and performing at your best, Pardi recommends that it’s useful to learn the fundamental components of good sleep (discussed here), maintain smart light rhythms day by day, and engage with the right tools to keep you mindful of your daily sleep practice. Sleep is hugely important in our health and these are some of the cutting-edge but practical techniques to help you get the best sleep possible. For even more guidelines to help you get a good night’s sleep, please see this previous article.


    Staff Writer

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