In a wellness market flooded by the latest gurus promoting expensive programs and products, I’m increasingly interested in focusing my blog on highlighting the freely available, nature-based elements that impact human health.
One of the most obvious and underrated of which is our relationship with light.
A while back I wrote a post extolling the power of spending adequate time in darkness (aka avoiding screens at night). I’ll recap the basics here but for a deeper look at the dark side of the light equation and its importance for human health, start with my first article.
Since I wrote it, screen addiction has been discussed ad nauseam in the media and we’ve likely all been saturated with messages regarding the hazards of blue light at night, so I won’t focus as much there. In this follow-up piece, I’d like to discuss the underrated power of exposing yourself to adequate natural light during the day. Despite its reputation in the media, blue light is not the problem. It’s the timing of blue light exposure that determines whether it is poison or medicine: bright, blue light is beneficial during the day and detrimental at night.
I’ll begin with a brief background on circadian biology, which explains why light matters.
How does our body keep time?
We evolved being exposed to predictable and alternating periods of light-dark every 24 hours. Our brains and cells evolved sensors to attune its physiology to the natural light-dark cycles in order to determine biological time.
More specifically, our master clock (the suprachiasmatic nucleus nucleus) in the brain entrains with light-dark cycles, as our optical nerve is constantly scanning the intensity and spectrum of light. The body is most sensitive to short wavelength light (blue light) and least sensitive to long wavelength light (like red light). In addition every cell in the body has clock cells which make up the peripheral clock. Our peripheral clock cells are most sensitive to metabolism (or in other words meal timing).
Timing physiological functions with light-dark cycles in nature led to more biological success. Historically, it made sense to be alert and active during daytime hours when food acquisition, preparation, and the majority of feeding most successfully occur. It made sense to sleep and focus on tissue repair and regeneration at night.
The field of chronobiology is helping us understand that optimal health occurs when the master clock (light is strongest cue) and the peripheral clock (meal timing is strongest cue) are in sync with each other and both are in sync with natural cycles of light and dark.
In other words, optimum health occurs when our sleep, meals, and light exposure inputs align with the natural cycles of light and dark.
THE POWER OF DARKNESS FOR HEALTH
Here’s a quick recap of why darkness matters. Bright, blue light at night signals to your biology that it is daytime. One of the way it signals this to your body is by blocking the release of melatonin in your brain. Melatonin, known as the “hormone of darkness,” relies on light intensity to know if it should be produced or blocked. If your eyes are sensing blue light at night, melatonin release doesn’t occur. We are all likely familiar with melatonin as a hormone (and supplement) that helps initiate sleep.
Perhaps more compelling is that melatonin appears to be a POWERFUL antioxidant, anti-inflammatory, and oncostatic (cancer-fighting) hormone that helps your body repair and heal at night. If you are deficient in DARKNESS, and thus deficient in melatonin, you won’t sleep as well but you are also lacking a powerful repair mechanism you evolved to expect in adequate quantities each day. Rather than spending your money on expensive antioxidant supplements (that likely don’t work), prioritize your daily dose of darkness instead.
How to actually make it happen!
Avoid looking at bright screens beginning ideally two hours before bed. Decide on a screen curfew time (at least one hour before ideal bedtime) and do your best to stick with it. Set a digital sunset alarm on your phone as a reminder. FUN FACT: TV screens (likely due to their distance from your eye) were shown to not decrease melatonin levels in the same way that personal devices do. Good news for us nighttime Netflix bingers :) Study linked here.
If you work a night shift or simply need to use a lot of electronic devices at night, consider wearing blue-blocking glasses. I like the Uvex brand, which you can buy on amazon. Additionally, download the f.lux program on your computer which blocks blue light as it gets dark: https://justgetflux.com/. Nightshift is the equivalent for Iphone http://www.apple.com/ios/preview/.
Use dim red-spectrum lights for night lights. Red light has the least power to shift circadian rhythm and suppress melatonin.
LIGHT IS THE NEW COFFEE
Morning light is the original coffee. Bright light in the morning gives our bodies a signal it’s daytime (known as daytime anchoring), which elicits a cascade of alerting hormones that make us energized and ready for the day.
Today, humans spend 90% of time indoors. This is problematic as many of us are not receiving adequate light cues to signal to our circadian rhythms that it’s daytime. It’s easy to assume that that indoor lighting is brighter than outdoor light, especially on a cloudy day. This isn’t true. The brightest lit office spaces are only around 500 lux, while being outside on a cloudy day exposes you to about 10,000 lux (and as much as 30,000 on a sunny day).
The impact of low light exposure on mood is illustrated in the modern understanding of Seasonal Affective Disorder (SAD) and the connection between low mood and lack of exposure to light in the winter. Too much time spent indoors is making it so that we are living in a chronic, low-light, “winter-like” environment. Studies have now found that exposure to bright light during the day positively impacts cognition, memory, energy, mood, and alertness (study here). Additionally, exposure to bright light during the day leads to better sleep at night and is protective against the harmful effects of blue light at night.
This means that most of us are exposed to inadequate, dim lighting environments during the day and too much light at night. In this environment, our bodies never receive a robust message as to whether it is biological day or night, which leads to circadian misalignment.
You can use light boxes or other high tech solutions but none are as elegantly designed for your physiology as simple sunlight. In the words of renowned light scientist Mariana Figueiro during her awesome Ted Talk on Light and Health, “Daylight is the ideal light source for the circadian system - it goes on and off at the right time, and is the right color and right intensity”.
Below are my top tips for harnessing the power of bright light during the day for optimal health.
How to actually make it happen!
The #1 practical way to get enough bright light during the day is by creating a morning walk habit. Go for at least a 10-30 minute walk each morning (ideally before 10:30am) and you will ensure you are getting adequate daylight anchoring each day. The most potent results happen within the first 30 minutes of exposure, so set this as a daily minimum for total time outdoors.
Get outside as much as possible during daylight hours. Particularly if you get groggy in the mid-afternoon, swap your coffee for a brisk walk outside.
If it is not possible to get outside during the day, consider using a light box of at least 10,000 lux in the morning. I haven’t used one myself but this looks like a good product.
*It’s important to mention that wearing sunglasses can reduce your bright light exposure by 7-15 fold, so don’t wear them on your walks where light exposure is the priority.
Like many topics, there are a lot of high tech, expensive ways to optimize sleep, energy, and moods. I argue that none are as potent and effective as intelligently using light-dark cycles to optimize your circadian rhythm. Light is an ally we co-evolved with. If we use the right spectrum and brightness at the right time, it has positive benefits on every system of the body. The best part is that it is free and democratically available as long as you have access to the outdoors!
As always, I’d love to hear about your own creative ways to optimize your circadian rhythm - feel free to post below!
If you need help improving your sleep and circadian cycle and are ready to transform your personal habits, I’d love to support you as your health coach. Click here to schedule a free consultation call.